A review of the potential constraints to crop production ... · compacted layer are from earlier...

A review of the potential constraints to crop production on sandy soils in low rainfall south-eastern Australia and priorities for research

A report for the GRDC Low Rainfall Zone Regional Cropping Solutions Network

31 July 2014

Murray Unkovich

School Agriculture, Food and Wine

The University of Adelaide

Citation;

Unkovich, MJ (2014) A review of the potential constraints to crop production on sandy soils in low

rainfall south-eastern Australia and priorities for research. A technical report for the Grains Research and

Development Corporation. Mallee Sustainable Farming, Mildura NSW.

Mallee Sustainable Farming Inc

152 Pine Avenue, Mildura, Vic, 3500

Phone: (03) 5021 9100 Email: [email protected]

PO Box 5093, Mildura, Vic, 3502

ABN: 99 557 839 332

This review has been written through funding provided by Grains Research & Development Corporation.

Acknowledgements

I am very grateful to the large number of people who have very kindly assisted with input for this report

in the form of the provision of data or their expertise. In no particular order I would like to thank the

following

Craig Liddicoat (Department of Environment, Water and Natural Resources, SA), Stephen Davies, Chris

Gazey (Department of Agriculture and Food, WA), Therese McBeath, Rick Llewellyn, Phil Ward, Mike

Wong, Margaret Roper (CSIRO), Richard MacEwan (Department of Environment and Primary

Industries, Vic,), Bob Holloway (Mintaro, South Australia), Sean Mason, Ashlea Doolette, Ann McNeill,

Cameron Grant, Fien Degryse, David Chittleborough (University of Adelaide), Alan MacKay, Nigel

Wilhelm (South Australian Research and Development Institute), Michael Moodie (Moodie Agronomy),

Rob Norton (International Plant Nutrition Institute), Brian Hughes, Dave Davenport and Amanda Schapel

(Primary Industries and Regions, SA), Neil Fettell (NSW). I would also like to acknowledge the

enthusiastic input from all of the attendees at the Sandy Soils workshop.

Foreword

The GRDC Low Rainfall Zone Cropping Solutions Network represents grain grower stretching from the

Central West of NSW, across the Victorian and South Australian Mallee, the Upper North region of

South Australia and across to the upper Eyre Peninsula. The group identified crop yields on sandy soils

across their regions to be well below water-limited yield potential, more so than for their finer textured

soils. The group determined that identifying the key yield limiting factors specific to representative sandy

soil types in the low-rainfall zone, and then to develop or extend commercially viable management

practices to improve production and water use on sandy soils was a high priority. This document begins

to tackle the first of these two issues, identifying key yield limiting factors on sandy soils, by collating

and analysing as much of the relevant information available in solution of sub optimal growth of crops

on coarse textured (sandy) soils across this low rainfall environment. The problems of sandy soils have

been apparent since agricultural lands were first cleared, but have perhaps been somewhat neglected in

favour of other soils which are easier to manage and are typically more productive. This initiative has

now put the considerable problems of farming sandy soils on the agenda, and with it great hope and

expectation for identification of new farming practices and technologies which will lift production on

these difficult soils and provide an incentive for more certain investment and returns on these soils. The

gap between potential and current yields achieved highlights an opportunity which if realised, will make a

substantial contribution to improved whole farm productivity. This report provides the foundation stone

for this journey.

Respectfully submitted

Murray Unkovich

31 July 2014

A review of the potential constraints to crop production on sandy soils in low rainfall south-eastern Australia and priorities for research

Contents 1 Introduction .......................................................................................................................................... 1

2 Sandy soils, general properties and challenges ..................................................................................... 3

2.1 Where do they occur in the target region? .................................................................................... 5

3 Potential limitations to crop growth in coarse textured soils ................................................................ 8

3.1 Water repellency ........................................................................................................................... 9

3.2 Soil pH ........................................................................................................................................ 12

3.3 Soil erosion ................................................................................................................................. 13

3.4 Crop root growth and water extraction ....................................................................................... 14

Deep ripping to increase rooting depth of crops ................................................................................. 19

3.5 Soil amelioration with clay or organic matter ............................................................................ 22

3.6 Crop nutrition ............................................................................................................................... 1

Nitrogen and sulphur ............................................................................................................................ 1

Phosphorus ........................................................................................................................................... 5

Potassium .............................................................................................................................................. 7

Micronutrients ...................................................................................................................................... 8

Deep placement of nutrients ................................................................................................................. 9

Nutrition summary .............................................................................................................................. 10

3.7 Soil carbon and biological fertility ............................................................................................. 10

3.8 Pests and diseases on sandy soils ............................................................................................... 11

3.9 Weeds and herbicides ................................................................................................................. 13

4 Water use efficiency as a measure of productivity ............................................................................. 14

5 System effects ..................................................................................................................................... 17

6 Summary and Conclusions ................................................................................................................. 19

7 References .......................................................................................................................................... 22

8 Appendix 1 – Workshop summary ..................................................................................................... 27

Phil Ward ............................................................................................................................................ 33

Neil Fettell .......................................................................................................................................... 34

Jeff Braun ........................................................................................................................................... 34

Andy Bates ......................................................................................................................................... 34

Workshop outcomes ........................................................................................................................... 35

9 Appendix 2 - Example soil descriptions ............................................................................................. 38

9.1 Murray Mallee ............................................................................................................................ 39

9.2 Eyre Peninsula ............................................................................................................................ 51

Index of Figures

Figure 1 Cropping zones of Australia. The region of interest in the present study is labelled in the figure as the “SA

Vic Mallee”. .................................................................................................................................................. 1

Figure 2 Relatively recent erosive forces have shaped many of the sandy rises in the Mallee regions. Here one can

see a second fence erected on top of the earlier fence, the barbed wire stand at the bottom being the top

strand of the earlier fence. In some cases a third fence has been erected. This erosion and deposition has

created soils extremely low in organic matter. ............................................................................................ 3

Figure 3 Areas in western Victoria where the soil is (A) predominantly sand (<15% clay), or (B) where sand occurs

but is is subdominant in the soil profile. The Victorian Mallee is defined within the upper solid black

boundary. Maps courtesy of Department of Environment and Primary Industries Victoria. ....................... 5

Figure 4 Areas of agricultural land in western Victoria indicated in yellow. The Victorian Mallee is defined within

the upper solid black boundary. Maps courtesy of Department of Environment and Primary Industries

Victoria. ........................................................................................................................................................ 6

Figure 5 Occurrence of sands over clays in South Australian agricultural lands. Map courtesy of Dept Environment,

Water and Natural Resources SA. ................................................................................................................ 7

Figure 6 Occurrence of deep sands in South Australian agricultural lands. Map courtesy of Dept Environment,

Water and Natural Resources SA. ................................................................................................................ 7

Figure 7 A sandy soil profile from Rankins Springs in central western NSW (photo courtesy of Michael Pfitzner).... 8

Figure 8 Comparison of the crop lower limit of water extraction and the drained upper limit in a toposequence

within a single field at Karoonda South Australia. The plant available water capacity of the soil ranged

from 31mm on the dune crest (A) to at least 116mm on the clayey soil on the adjacent flat (C). Figure

courtesy of Therese McBeath, CSIRO. ........................................................................................................ 15

Figure 9 A sandy soil from Rankins Springs in central western NSW where water has been onserved remaining in

soils after crop harvest (photo courtesty of Michael Pfitzner). .................................................................. 17

Figure 10 Change in penetration resistance of a sandy soil with depth, following deep (0.6m) ripping at Loxton in

South Australia (from Sadras et al. 2005). ................................................................................................. 20

Figure 11 Exposure of an impenetrable layer in a sandy soil at Corrigin in Western Australia. The furrows in the

compacted layer are from earlier deep ripping. Photo courtesy of Dr Chris Gazey, Department of

Agriculture and Food Western Australia. ................................................................................................... 20

Figure 12 Clay delving (left) and (right) a spading machine for clay incorporation into a sandy surface soil .......... 22

Figure 13 Total nitrogen (%) in the top 10 cm of dune and swale soils at three sites in north west Victoria. The soil

at the Karawinna site is a sandy across the whole site (From Moodie 2012b). ........................................... 2

Figure 14 Mineralisable nitrogen in dune and swale soils at sowing of a second wheat crop in 2012, following a

range of of break crops two years previous at Karoonda in the South Australian Mallee. The

toposequence runs up a slope from a clay flat (Swale) to a sandy rise (Dune) . (from McBeath et al.

2013c). ......................................................................................................................................................... 2

Figure 15 Crop grain yield response to N fertiliser application for a fifth (A) or seventh (B) consecutive wheat crop in

a toposequence at Karoonda in the South Australian Mallee (from McBeath et al. 2011 and McBeath et

al. 2013b). .................................................................................................................................................... 3

Figure 16 Fixation of soil P as a function of soil pH. (Adapted from Glendinning 1999) .............................................. 6

Figure 17 Variation in proportion of available Phosphorus with depth as a function of landscape position and soil

type in a single field at Karoonda, South Australia (data courtesy of S. Mason, University of Adelaide). ... 7

Figure 18 Organic carbon (%) in the top 10 cm of dune and swale soils at three sites in north west Victoria. The

Karawinna site is a sandy across the whole field. Data from Moodie (2012b). ........................................ 11

Figure 19 Change in Rhizoctonia (R. solani AG8) DNA density in soil under different crop rotations over the summer

fallow period at Waikerie in the Murray Mallee. Clouds indicate rain events and arrows tillage events

(from Gupta et al. 2010). ........................................................................................................................... 12

Figure 20 Rhizoctonia solani (AG8) inocula concentrations under a range of crops (following wheat) across the

toposequence at Karoonda (from Gupta et al. 2012b). ............................................................................. 12

Figure 21 Average weekly open pan evaporation and average weekly rainfall totals for Walpeup, in the Victorian

Mallee. ....................................................................................................................................................... 15

Figure 22 Relationship between (A) evaporation from soil, plant transpiration and seasonal dry matter (DM)

production, and (B) transpiration efficiency and dry matter production or grain yield (GY), and (C)

introduction of radiation limited growth at luxury water supply. ............................................................. 15

Figure 23 Break crop effects (t/ha) reported by farmers in the Victorian Mallee following canola or pulse crops on

dunes (sand), mid-slope (loam) or heavy (swale) soils. ............................................................................. 18

Figure 24 Opportunities for mitigating current constraints and bringing crop yields closer to water limited yield

potentials on sandy soils, and for soil reformation through more radical amelioration strategies........... 35

Index of Tables

Table 1 Approximate physical properties of some soil classes based on sand and clay content (adapted from

Brady and Weil 1999) ................................................................................................................................... 4

Table 2 Areas of sandy soils (ha) in South Australian agricultural lands of the Murray Darling Basin and the Eyre

Peninsula ...................................................................................................................................................... 6

Table 3 Comparison of wheat anthesis shoot dry matter and grain yield for crops grown on sandhill or interdune

soils at Walpeup, Victoria (from Walsh 1995).............................................................................................. 9

Table 4 Water repellency as a function of landscape position and soil type in a single field at Karoonda, South

Australia. (data courtesy of T. McBeath CSIRO). ........................................................................................ 10

Table 5 Soil bulk density and pH as a function of soil depth and landscape position for a single field at Karoonda,

South Australia. (Data courtesy of T. McBeath CSIRO) .............................................................................. 12

Table 6 Shoot and root dry weights for barley grown in pots containing unamended soils sourced from different

depths from a sandhill profile at Walpeup, Victoria (from Walsh 1995) ................................................... 13

Table 7 Plant available water capacity (mm) for wheat crops across a paddock toposequence at different sites in

the SE Australian Mallee. Data from Moodie 2010). ................................................................................. 16

Table 8 Analysis of non-wetting soils prior to clay addition (A) or after clay addition (B) in the south Australian

Murray Mallee. (from Eldridge and Hughes 2006) ....................................................................................... 1

Table 9 Macronutrients in a sandhill soil profile at Walpeup, Victoria. from Walsh (1995) ..................................... 1

Table 17 Anthesis dry matter and grain yield for barley grown in different landscape position at Walpeup, Victoria

(from Walsh 1995) ......................................................................................... Error! Bookmark not defined.

Table 10 Plant available (mineral) nitrogen (kg/ha) at sowing of a seventh consecutive wheat crop in 2012 at

Karoonda in the South Australian Mallee (from McBeath et al. 2013b). ..................................................... 3

Table 11 Plant available (mineral) nitrogen (kg /ha) in the top 1m of soil at sowing for consecutive wheat crops at

Karoonda in the South Australian Mallee. Annual N fertiliser rates applied after soil sampling are given in

parentheses. (data from T McBeath, CSIRO). ............................................................................................... 4

Table 12 Soil nitrate-N (kg N/ha) in a toposequence at Karoonda at sowing of a wheat crop in 2010(from McBeath

et al. 2011) ................................................................................................................................................... 4

Table 13 Soil fertility indicators as a function of landscape position and soil type in a single field at Karoonda,

South Australia. (data courtesy of T. McBeath CSIRO). ................................................................................ 6

Table 14 Variation in Phosphorus buffering index with depth as a function of landscape position and soil type in a

single field at Karoonda, South Australia (data courtesy S. Mason, University of Adelaide). ...................... 7

Table 15 Risk of micronutrient deficiency for Australian soil orders. From Norton (2013). ........................................ 8

Table 16 Shoot dry matter and grain yield of wheat as a function of landscape position and soil type in a single

field at Karoonda, South Australia (from Whitbread et al. 2010) .............................................................. 16

Table 18 Percentage of cropping area sown to cereals, grain legumes or canola in the 2011 agricultural census . 19

Table 19 List of attendees at the workshop on potential constraints to crop production on sandy soils in low

rainfall south-eastern Australia and priorities for research. ................................................................... 27

Table 20 Comments on original scoping paper primary recommendations as follows ......................................... 29

Table 21 Research questions raised by workshop participants in relation to mitigation of problems of crop

production on sandy soils ......................................................................................................................... 30

Table 22 Extension questions raised by workshop participants in relation to mitigation of problems of crop

production on sandy soils ......................................................................................................................... 31

Table 23 Questions raised by workshop participants in relation to amelioration of sandy soils with clay and/or

organic matter amendments .................................................................................................................... 32

Executive summary

Coarse textured (sandy) soils which by definition have a very low clay content represent approximately

30% of cropping soils in the low rainfall SE Australian cropping region. An area which is characterised

by low rainfall and low fertility soils. Opportunities for increasing crop production are probably

substantial on these soils because crop yields appear to be well below the water-limited potential.

Significant soil constraints might be overcome with judicious management informed by solid science.

The primary opportunities lie in a better understanding of soil water extraction by crop roots, and the

nutrient dynamics associated with water movement within the crop root zone. Crop nutrition and crop

rotations will also play a key role in lifting crop root growth in time and in space and thereby increase

total crop water and nutrient use. Soil compaction, either natural or traffic induced may be a significant

limitation, the extent and causes of which need to be ascertained. If these opportunities can be realised

then soil organic matter may be raised on sands, providing significant whole system benefits.

The primary challenges on coarse textured soils in low rainfall SE Australia are thus:

ensuring that crops grown have deep rooting capacity and deep rooting opportunity

ensure that nutrients are accessible within the crop rooting zone

that crop rotations include more frequent broad leaf species

the movement of water and nutrients down the soil profile are understood to the extent that they

can be predicted

the extent of non-wetting and high soil resistance to root growth across the region are better

defined

the specific causes of high soil resistance to root growth are identified

to increase soil organic matter and thereby improve chemical, biological and physical fertility

Further opportunities in revolutionary soil amelioration, involving additions and incorporation of clay and

organic matter to soils have been trialed by many farmers and offer the possibility of a more elevated crop

yield plateau. Considerable research would be required to provide predictive capacity with respect to the

efficacy of these practices and thus the returns on the substantial investment required to deploy these on-

farm. In the meantime the challenges listed above can be progressed with a combination of basic,

strategic and applied research, and adaptation and extension of existing technology from elsewhere in

Australia.

Inherent Sand Potential

Reduced Sand Potential

Raised Soil Potential

Poor root growthWater repellencyLow fertilityDeclining soil CRotational crops

AM

ELIO

RA

TIO

N

MITIGATION OF

AMELIORATION BY

ClayingDelvingDeep rippingSoil reformingDeep nutrients

$

$

Establishment NutritionWeeds DiseaseRotations

Ongoing management

For each of these recommendations it is important that research questions are carefully framed, and

relevant material thoroughly examined, prior to any experimental work being planned. Much can be

learnt and adapted from Western Australian research into water-repellency on sands and extended to low

rainfall SE Australia. Many of the other questions can be answered with specifically targeted research,

rather than large scale programs incorporating many treatments and few measurements. This document

provides a background not a plan for action. The opportunities are significant but will only be realised

through the prosecution of experiments based on specific, well informed, clearly framed hypotheses.

Potential constraints to crop production on sandy soils

1 Introduction

This review is concerned with the coarse textured soils of the low rainfall grain cropping zone in north

western Victoria (and adjacent NSW), the South Australian “Murray Mallee”, Upper North of South

Australia, and the Eyre Peninsula in South Australia (Figure 1). This target region is characterised by a

very high evaporative demand relative to rainfall, making it one of the driest cropping environments in

Australia. In addition to a sparing and erratic water supply, another characteristic of the region is a range

of soils which are inherently low in fertility and organic matter, making it one of the most fragile

cropping environments on the continent (Coventry et al. 1998). The landscape is made up of a mosaic of

soils, coarse textured soils of neutral to alkaline pH which are either deep, or shallow and overlay calcrete

rubble or clays. Sodicity, salinity and or phytotoxic boron may be associated with the clays in some cases.

While the region features a range of sandy soils, the soils of interest are primarily deeper sands with the

great majority of the seasonal plant available water and annual crop root growth in the sandy layer.

Texture contrast soils with shallow sands over clays, clay loams or calcrete layers, which are also

common in the region, are not the focus of this review. Some of the problems with texture contrast soils

were investigated in an earlier GRDC initiative on “subsoils” (see Price 2010).

Figure 1 Cropping zones of Australia. The region of interest in the present study is labelled in the

figure as the “SA Vic Mallee”.

Potential constraints to crop production on sandy soils Page 2

Newell (1961) describes the agricultural development of the soils at Walpeup in the Victorian Mallee in

the first part of the 20th century, this probably reflects what has happened elsewhere…

“Agricultural practices have been a marked impact on the soils of the Mallee. Clearing of the more

favoured parts for wheat-growing commenced about 1890 and, by the turn of the century this was the

main agricultural pursuit. The then current practices of bare fallowing and stubble-burning, assisted by

the activities of rabbits, were conducive to blowing of the light surface soils. This was accelerated as

settlement immediately following the 1914-1918 war pushed cultivation into margin areas. Soil erosion

reached disastrous proportions by 1930. Its effects are evident on the Research Station. The narrow

shelter belt in paddock No. 6 has given rise to a north-south sand dune about 15 ft high. Subsoil is

exposed in many places as in paddock No. 3 while surfaces have been altered elsewhere. Sand sheets in

paddock Nos 1, 2, 3, 7 and 9 appear to date from this erosive period.”

Soil erosion has now been largely arrested, although this position is still precarious in some situations.

The great improvement is due to the amalgamation of properties into larger farming units with greater

emphasis on grazing sheep, assisted by a succession of favourable seasons, and in part to changes in

farming methods developed on the Research Station since 1939. Principally these are the use of barrel

medic pasture in rotation with cereals, and trash fallowing in place of stubble burning.

……..There is usually a well defined zone of organic darkening 4 to 8 in. deep, in both virgin and

cropped areas, though this may be blown away in some cases, or in others covered by recently drifted

sand. Sand sheets in extensive, uncleared areas have apparently originated from wind action on

neighbouring fallows….exceptional drifts up to 15 ft deep, are mapped…”

Thus while the sandy soils of low rainfall SE Australia may not be of aeolian (wind deposited) origin

(Pell et al. 2001), many of them have been reformed by wind following agricultural development (see

Figure 2). This has effectively resulted in new soils beginning to form at a local scale, on top of the

regional land systems and soils. While the earlier erosive processes have been very much reduced by

contemporary practices (Cooke et al. 1989), they cannot be completely eliminated on these soils.

Pell et al. (2001) recognised two dune systems in the SE Australian Mallee, the Lowan Sands and the

Woorinen Formation. The Lowan Sands are characterised by a lack of bonding clay and carbonate and the

absence of soil development, where dunes occur they tend to be west-south west facing. They often have

bleached layers. In contrast the Woorinen formation sands are calcareous in nature and contain some clay,

they are typically found in closely spaced east-west dunes. Lowan sands are also found on the upper Eyre

Peninsula. “Moomba”, (calcareous red) sands have also been defined in South Australia, these are more

fertile and less water repellant than Lowan Sands (Jeffrey and Hughes 1995).


Figure 2 Relatively recent erosive forces have shaped many of the sandy rises in the Mallee regions.

Here one can see a second fence erected on top of the earlier fence, the barbed wire stand at the bottom

being the top strand of the earlier fence. In some cases a third fence has been erected. This erosion and

deposition has created soils extremely low in organic matter.

2 Sandy soils, general properties and challenges

Sandy soils are characterised by their grain size, typically having low clay content and being dominated

by coarse particles (Table 1). This coarse texture confers certain physical properties on the soils which

influence the ability of the soil to hold water (Table 1), and therefore its biological activity. The low clay

content associated with sandy soils also has several physical, chemical and biological drawbacks. The

lack of clay reduces the physical protection of organic matter in soils, increasing the rate of organic

matter breakdown. While this can have a positive effect in increasing mineral nutrient availability in soils,

sandy soils have a very limited capacity to “hold” these elements in the soil because sands tend to have a

low ion exchange capacity, ions can thus be readily leached down the soil profile and out of the reach of

plant roots and microbes. Thus compared to finer textured soils, sands generally have lower physical,

chemical and biological fertility.

In terms of water holding capacity, sandy soils have larger pores than finer textured soils, making it more

difficult to hold soil water against gravity and consequently sandy soils have a lower capacity to store soil

water for plant uptake. Conversely, sandy soils have a lower surface area which means that less water is

tightly bound to soil particles (hygroscopic water) and plants can extract a higher proportion of the total

water from the soil (a lower, lower limit of extraction. Table 1). In a mallee sand in Victoria only about

20% of the soil pore space was occupied by water at field capacity, providing a maximum of only 63mm


of plant available water in the top 2m of soil ((Walsh 1995).Coarse textured soils sometimes support

better crop growth in strongly water limited seasons because when the soil water content is low plants can

extract a greater fraction of the water in the soil from sands than clays. Furthermore, many crops are able

to root deeply on some sandy soils (Tennant and Hall 2001), thus the total available water capacity can

sometimes be higher in sandy soils than adjacent finer textured soils.

Table 1 Approximate physical properties of some soil classes based on sand and clay content

(adapted from Brady and Weil 1999)

Sand content

(%)

Clay

content

(%)

Drained upper

limit

(% water w/w)

Lower limit of

extraction

(% water w/w)

Available water

capacity

(mm/m soil depth)

Sand >75 5 14 4 100

Sandy loam 55-65 10 18 7 120

Loam 30-55 10-30 30 13 220

Clay loam <30 30-40 34 18 210

Clay <30 >40 42 25 160

The lack of organic matter, low water holding capacity and low clay content mean that sandy soils do not

tend to “aggregate” and thus are very susceptible to wind and water erosion if there is no surface cover

from living plants or from plant residues. Erosion of sandy soils has been an ongoing problem across

much of low rainfall southern Australia and in a recent assessment (Smith and Leys 2009) was rated as

widespread on sandy soils across the Mallee systems in NSW, Victoria and South Australia, including the

Eyre Peninsula. In some areas within this zone it was rated as severe. The region was considered the

highest priority for wind erosion control in the national assessment of Smith and Leys (2009).

These coarse textured soils may be derived from siliceous, or carbonaceous parent material. The siliceous

soils in the region can be mildly acidic but are primarily neutral-alkaline in pH, while the carbonaceous

soils are by nature alkaline, often strongly so. The differing pH of these soils confers different inherent

soil fertilities and nutrient toxicities. Nutrient deficiencies of nitrogen, phosphorus, sulphur, zinc,

manganese, copper, cobalt, boron, molybdenum and selenium have been recorded for sandy soils across

low rainfall south eastern Australia. If carbonate is also present in these soils, it can greatly reduce the

availability of phosphorus, manganese, zinc and iron (Holloway et al. 2001).

One advantage of coarse textured soils is that they tend not to suffer from primary salinity because excess

salts are readily leached down the soil profile and into the groundwater systems. Conversely, they can

suffer from secondary salinity where groundwater rise brings salt with it to the surface, or near surface,

where it can be concentrated through evaporative water losses.


2.1 Where do they occur in the target region?

The main soil orders across this region are Calcarosols (Typically EP, SA Mallee Vic Mallee), Sodosols

(Typically eastern EP, Northern Vic Mallee) Tenosols (Typically western EP, northern Mallee) ,

Vertosols (Typically Wimmera), and Chromosols (scattered, typically Upper North, east of Burra Hills to

Robertstown in South Australia, and parts of western Victoria, see McKenzie et al. 2004). The primary

soils of interest in the present analysis have various classifications, depending on the level to which each

of these orders can be subdivided. Most are within the Tenosol, Calcarosol or Sodosol groups. In the

central Mallee of Victoria sandy dunes make up about 30% of the landscape (Rowan and Downes 1963).

Siliceous sand hills occur in dune-swale systems right across the low rainfall SE Australia from north-

western Victoria to the Eyre Peninsula. These dune overlay heavier textured soils, often with a strong

texture contrast. At Karoonda McBeath et al. (in prep) describe a “Kandosol (deep sand) on a dune crest,

a Calcarosol- mid-slope (sand over clay loam) and a clay loam over clay, Chromosol, in the swale. There

are however significant variations in the development of these sandy soils and the dune swale systems

across the region and many local variants can be recognised (see e.g. Hall et al. 2009). Calcarosols make

up almost 60% of the soils of the Eyre Peninsula, and Tenosols a further 20%. Examples of a few sandy

soil profiles from South Australian low rainfall cropping areas are given in Appendix 2, but there are too

many variants to be able to be defined in the present analysis. A general overview of the occurrence of

sandy soils in the cropping areas of Victoria and South Australia is given below.

Figure 3 Areas in western Victoria where the soil is (A) predominantly sand (<15% clay), or (B)

where sand occurs but is subdominant in the soil profile. The Victorian Mallee is defined within the upper

solid black boundary. Maps courtesy of Department of Environment and Primary Industries Victoria.

A B


Figure 4 Areas of agricultural land in western Victoria indicated in yellow. The Victorian Mallee is

defined within the upper solid black boundary. Maps courtesy of Department of Environment and

Primary Industries Victoria.

The area sown to crops in 2010 within the intersection of the Mallee area in Figure 3 was 388,000 ha,

21% of the total cropped area in the region, however, the total area of sandy soils used for agriculture in

the region would be much higher than this because this figure does not include land under pasture or

fallow.

The Atlas of Key Soil and Landscape Attributes (Rowland 2001) records 3.6 mill. ha of sands in the 10

mill. ha of agricultural lands of SA, and 1.4 mill. ha of sand over clay. Deep sands thus make up 36% of

the agricultural soils of South Australia (Table 2 and Figures 5 and 6).

Table 2 Areas of sandy soils (ha) in South Australian agricultural lands of the Murray Darling Basin

and the Eyre Peninsula

Soil Group Description SA Murray-Darling Basin Eyre Peninsula

G1 Sand over sandy clay loam 9,421 97,734

G2 Bleached sand over sandy clay loam 41,562 59,337

G3 Thick sand over clay 92,831 65,675

G4 Sand over poorly structured clay 97,167 76,951

G5 Sand over acidic clay 0 5,673

H1 Carbonate sand 395 75,903

H2 Siliceous sand 148,510 328,091

H3 Bleached siliceous sand 91,215 170,347

I1 Highly leached sand 0 1,220

I2 Wet highly leached sand 0 1,117

Total ha 556,608 806,539


Figure 5 Occurrence of sands over clays in South Australian agricultural lands. Map courtesy of Dept

Environment, Water and Natural Resources SA.

Figure 6 Occurrence of deep sands in South Australian agricultural lands. Map courtesy of Dept

Environment, Water and Natural Resources SA.


Figure 7 A sandy soil profile from Rankins Springs in central western NSW (photo courtesy of

Michael Pfitzner).

3 Potential limitations to crop growth in coarse textured soils

The potential key limitations to crop production on sandy soils in the region are highlighted in this

section. While some of these problems are not restricted to coarse textured soils, the report attempts to

focus on those aspects which relate more specifically to such soils. Many of the constraints are

inextricably linked, such that there is considerable overlap between some of the headings, especially in

the opportunities for management.

Yields on sandy soils are often lower than on adjacent finer textured soils because of lower physical,

chemical and biological fertility. The report leans heavily on a few study sites on what are known as

dune-swale systems where there have been direct comparisons between the sandy dune soils and the

adjacent finer textured soils on the “swales”. These are very useful, because they have the soil types as

the primary contrast, with climate being identical (except perhaps for frost) and management being as

close to the same as is practical. Such studies thus allow a definition of processes and properties unique to

the sandy soils of the region. It is however recognised that not all relevant sandy soils in the target region

are situated in such dune-swale systems. An illustration of the relatively poor performance of coarse

textured (sandhill) soils relative to finer textured (interdune) soils is shown in Table 3. Here it can be seen

that crop shoot dry matter, grain yield and harvest index were all consistently lower on the sand than the


interdune soil. Based on the in-crop rainfall it can be seen that the efficiency of water use was very much

lower on the sand than the finer textured soil. Based on the rainfall use efficiency one would thus

anticipate that the potential for yield improvement would be significantly greater on the sands than the

finer textured soil. Within a single season in a single field, the gross margin on the more sandy parts of

the field was less than half of that on the soils elsewhere in the field with a higher clay content (Karoonda,

SA, McBeath et al. 2013a).

Table 3 Comparison of wheat anthesis shoot dry matter and grain yield for crops grown on sandhill

or interdune soils at Walpeup, Victoria (from Walsh 1995).

Year In-crop Sandhill soil Interdune soil

rainfall Anthesis DM Grain yield Anthesis DM Grain yield

(mm) (t/ha) (t/ha)

1988 273 1.30 0.20 4.59 2.68

1989 243 1.91 0.20 4.45 2.57

1990 234 1.12 0.11 2.44

1991 226 0.70 0.11 4.38 2.06

1992 384 1.74 0.47 4.01

mean 247 1.35 0.22 4.47 2.75

Coventry et al. 1998 described the (mainly calcareous) sandy soils of the Eyre Peninsula and the primary

challenges facing farmers cropping on these soils as phosphorus, manganese and zinc deficiency, root

pests and diseases and water repellency. Problems associated with fine textured subsoils were also

considered widespread.

3.1 Water repellency

In water repellent (non-wetting) soils water does not infiltrate the soil surface in an even manner,

resulting in dry patches and increased water run-off. For crops this often causes poor germination and can

also reduce nutrient availability because crops cannot access nutrients in dry soil patches. Poor crop

establishment subsequently increases the risk of wind erosion and increased run-off can also cause soil

erosion. The problem is primarily caused by waxes produced in the soil during breakdown of crop and

pasture residues. The low surface area of soils with low clay contents results in these waxes coating a

larger fraction of the soil surfaces and/or filling soil pores more easily, resulting in water repellency. This

is primarily a problem for soils with a clay content of <3%. In such sandy soils only 1-3% of the sand

grains need be coated with hydrophobic compounds to induce water repellency (Steenhuis et al. 2005).

Table 4 highlights the difference in water repellency within a single field at Karoonda as a function of

changing soil texture


In South Australia >900,000 ha of agricultural land are thought to be susceptible to strong water

repellency (Rowland 2001). These areas are primarily on sands in the Murray Mallee, south of Kimba on

the Eyre Peninsula, and in the south east of the State. The Tenosols are particularly susceptible to water

repellency (Jeffrey and Hughes 1995).

Table 4 Water repellency as a function of landscape position and soil type in a single field at

Karoonda, South Australia. (data courtesy of T. McBeath CSIRO). In this case repellency is taken as the

time (seconds) it takes for a drop of deionised water, placed on the soil surface, to infiltrate the soil.

Values above ca 200 seconds would indicate moderate water repellency.

Topography Soil Description Water Repellency

(seconds)

Swale Clay-loam over clay 1

Swale 3

Mid-slope 31

Mid-slope Sand over clay loam 205

Mid-slope 246

Crest Deep sand 201

Dune 224

Dune 260

Uneven wetting at the break of the season resulting from water repellency can also cause staggered weed

germination with consequences for herbicide efficacy. Furthermore, if a non-wetting soil wets up only to

dry out again, the non-wetting nature of the soil returns, and thus a series of weak rainfall events can be

very ineffective for germination on water repellent soils (Roper 2005). This has great implications for

both sown crop emergence and weed control.

A comprehensive review of the management of water repellency in Australian soils has recently been

completed (Roper et al. 2014). That review details amelioration strategies, practices which remove the

water repellency, and mitigation practices which try to minimise the effect of the repellency on crop

production. Low cost mitigation options tend to result in short-term, single season, responses, but options

for longer term amelioration are more expensive. We focus here on mitigation practices. Since

amelioration strategies involve a raft of changes to soil properties in addition to water repellency, these

are discussed in Section 3.5.

Crop establishment is the major problem. Sowing of crops into the previous year’s row can assist as

biopores provide very important water infiltration channels in minimum tillage systems. While

channeling of water into furrows carries the risk of excessive preferential flow and leaching of mobile

nutrients and pesticides (Blackwell 2000) and also carries the risk of movement of herbicides into the


seed row, furrow sowing technology has been successfully developed for non-wetting sands in Western

Australia (Blackwell et al. 2014), using winged points or boots, wetter formulations and sowing near or

between previous crop rows. In other studies in Western Australia (Roper et al. 2013) the combination of

stubble retention and minimum tillage resulted in good soil water infiltration despite persistent non-

wetting of the surface soils. This may be a result of preferential flow of water. Thus while increased

organic matter input was associated with the production of more hydrophobic compounds in soils, this

may not necessarily result in decreased water infiltration.

Water repellency of sandy soils can be reduced through the addition of clays, sourced either externally,

and spread on the surface, or “delved” from the subsoil in situ in some cases. Interestingly, in studies in

Western Australia, the clay itself was only able to explain about 20% of the variance in reduced water

repellency following addition (McKissock et al. 2000) and so the mechanisms are not entirely clear.

Spreading of clay on to the acid sands of the south-east of South Australia has generally doubled crop

yields (Cann 2000). Studies on acid sands in Western Australia (Hall et al. 2010) indicated that a clay

content above 3% was required to alleviate water repellency and improve crop yield. Yields were

improved by a combination of increased seedling establishment, better plant nutrition (especially K which

came with the clay), and greater water infiltration and more even wetting of the soil. All of these

mechanisms are likely to apply to sandy soils in low rainfall SE Australia, although K deficiency is yet to

be demonstrated there.

Water repellency of soils may exhibit temporal variation, but not merely as a function of soil water

content. Evidence for hydrophobic compounds moving down the soil profile through leaching, and for

microbial activity breaking down waxes have been presented (Hardie et al. 2012; Roper 2005). On acid

soils addition of lime and increasing soil pH may stimulate the activity of wax degrading microbes and

reduce repellency (Roper 2005). Promoting microbial activity should thus reduce water repellency. While

strains of wax-degrading bacteria have been isolated and found to reduce the repellence from severe to

low in laboratory experiments under ideal conditions, reducing repellence by inoculating paddocks with

these wax degrading organisms is limited by competition from other soil micro-organisms and

insufficient soil moisture to maintain effective populations and activity of the introduced organisms

throughout the year. Attempts to introduce microorganisms to the soil to assist in breakdown of

hydrophobic compounds have not been as successful in the field as in the laboratory. Only marginal

improvements in wettability were observed in field experiments in Western Australian acid sands (Roper

2006). Whether such organisms would persist in soil over time and be able to maintain improved

wettability is yet to be ascertained.

Management options for water repellency are available and are being implemented in Western Australia

where there has been considerable research investment. Soils affected in WA are mostly deep pale sands,


sandy duplex soils and sandy gravel soils. The problem may affect some 3.3 mill ha of soils in WA. In a

recent review of management of water repellent soils Roper et al. (2014) stated that the primary questions

which remained unanswered in relation to mitigation of repellency were the interaction between dry

seeding and water repellency, and the possible role of biological soil amendments in management.

3.2 Soil pH

Acidity is generally not a major problem across the zone but high soil pH is likely to influence

availability of nutrients. Calcareous soils usually have some (1 to 90%) carbonate associated with them,

primarily as calcium carbonates and these sparingly soluble salts result in a soil a pH of 8.0–8.2 which is

generally not a severe problem for plant growth or agricultural production. However, problems are

encountered in alkaline soils when sodium accumulates and forms salts such as sodium bicarbonate and

sodium carbonate. These are highly soluble and increase the soil pH above 8. When the pH is more than

9, the soils are considered highly alkaline and often have toxic amounts of bicarbonate, carbonate,

aluminium and iron (Rengasamy 2013).

Table 5 Soil bulk density and pH as a function of soil depth and landscape position for a single field

at Karoonda, South Australia. (Data courtesy of T. McBeath CSIRO)

Relative position Depth (cm) Bulk density pH (1:5 H2O)

Swale 0-10 1.37 7.44

10-20 1.35 8.78

20-40 1.41 9.33

40-60 1.65 9.58

60-80 1.72 8.45

80-100 1.72 6.42

Mid-slope 0-10 1.59 8.12

10-20 1.56 9.41

20-40 1.85 9.70

40-60 1.76 8.79

60-80 1.71 6.32

80-100 1.71 7.24

Crest 0-10 1.58 6.32

10-20 1.62 7.24

20-40 1.62 8.00

40-60 1.80 8.71

60-80 1.54 9.20

80-100 1.73


The pH (H2O) of four non-wetting sands from the southern SA Mallee ranged from 6.7 – 7.2 (Eldridge

and Hughes 2006). High soil pH at depth in sandy Mallee soils may be an impediment to root growth and

water uptake. While it is also high in swale and mid-slope soils (Table 5) crops do not need to root as

deep in finer textured soils because more water and nutrients are typically held nearer the surface. Walsh

(1995) reported soil pH (CaCl2) on a Mallee sand to range from 8 at the surface to 9 at 1m and 9.5 at 2m

depth, and in a pot experiment growing barley in each 20cm soil increment, plants grew well in the layers

with pH>9 (Table 6). He concluded that nutrition rather than pH or salinity were likely candidates for

poor growth on sandhill soils. However, in the same pot experiments barley seedlings responded to acid

addition alone, and this was interpreted to be a possible response to bicarbonate toxicity.

Table 6 Shoot and root dry weights for barley grown in pots containing unamended soils sourced

from different depths from a sandhill profile at Walpeup, Victoria (from Walsh 1995)

Depth (cm) pH

(CaCl2)

Shoot DW

(mg)

Root DW

(mg)

0-20 7.9 15.6c 106

20-40 8.2 16.3c 120

40-60 8.3 25.0a 110

60-80 8.4 22.6ab 106

80-100 8.6 25.1a 102

100-120 8.7 25.1a 94

120-140 8.8 27.4a 104

140-160 8.8 22.3a 88

160-180 9.0 25.1a 86

180-200 9.1 18.4bc 92

It is clear from the above that many sandy soils in low rainfall SA Australia have high pH, what is not

clear is whether pH per se could restrict root growth, or whether the primary effects might relate to

nutrient deficiencies and nutrient toxicities. It should be noted that soils with a pH >5 should be measured

in water because with CaCl2 as an extractant some of the carbonate and bicarbonate in the soil will

become bound to the Ca from the extract and thus lower the measured pH.

3.3 Soil erosion

An assessment of soil susceptibility to erosion in the Mallee rated coarse sands less susceptible to wind

erosion than fine-medium sands and sandy loams/loamy sands (Anon 2011a). The east-west dune system

in the central Victoria Mallee was rated the highest risk of wind erosion. Wind erosion risk in the region

is primarily a function of soil cover, especially during the period between crop harvest and establishment


of the following crop the next winter (Anon 2011b; Anon 2013a). There was no greater risk of erosion on

sand dunes than on slopes or swales in recent studies of break crops (Anon 2013a). The highest erosion

risk was following fallow or hay crops. The wind erosion risk of sandy soils is primarily early in the life

of the crop when both leaf area and groundcover are low. In extreme cases crop establishment might be

compromised, however, the impact of sandblasting on final crop yield for an established crop may be

greater later in the life of a crop than earlier (Bennell et al. 2007).

Problems with establishment of canola on sandy soils in the region have been documented (Anon 2013b)

but are not restricted to sands. Establishment is compromised by a weak seasonal break (low soil water

content) which leads to poor establishment and subsequent greater susceptibility to wind erosion. Water

repellency would also lead to poor germination and increase the risk of wind erosion. The erosion risk

following grain legume crops such as field pea and chickpea, is very high on coarse textured (dune) soils

of the Mallee (Moodie 2012a). However, for other broad leafed crops the risk of erosion can be managed

by sowing break crops at recommended densities and retaining all stubble. The erosion risk on coarse

textured soils was greatest under fallow and hay systems where there was lower stubble cover (Clough

2012).

3.4 Crop root growth and water extraction

In deep sandy soils many crops have been shown to root to well over 1m depth (Tennant and Hall 2001),

and some annual crops such as lupin (Hamblin and Hamblin 1985; Unkovich et al. 1994), wheat (Incerti

and O'Leary 1990) and cereal rye (Hamblin and Tennant 1987) can develop roots and extract water to

more than 2m depth. There is however substantial evidence to show that root growth of crops in sandy

soils in low rainfall SA Australia may be much more limited.

Water extraction on a sandy rise was restricted to ca 45cm at Karoonda, whereas water extraction

continued to at least 1m on the adjacent mid-slope and associated flat (Figure 8). This resulted in a

potential plant available water storage of only 31mm for crops on the crest of the sandy rise. Clearly the

inability of crops to extract water below 30cm greatly reduces the yield potential in these coarse textured

soils. The depth of this layer (30-35cm) is similar to the compacted layer observed in earlier studies in the

South Australian Mallee (Sadras et al. 2005). However, factors other than resistance to root penetration

may also contribute to poor root growth at depth, including accumulation of ions or organic chemicals

hostile to plant roots, or a lack of nutrients in soil. Investigation of why roots do not penetrate below these

subsurface layers is warranted. Similar observations have been made on sandy soils in a different land

system in western NSW (Barry Haskins pers. comm.).


Dep

th (c

m)

Volumetric water content (%)

(A) Dune crest (31 mm)

(B) Mid slope (>110 mm)

(C) Flat (>116 mm)

Crop lower limitDrained upper limit

Figure 8 Comparison of the crop lower limit of water extraction and the drained upper limit in a

toposequence within a single field at Karoonda South Australia. The plant available water capacity of the

soil ranged from 31mm on the dune crest (A) to at least 116mm on the clayey soil on the adjacent flat (C).

Figure courtesy of Therese McBeath, CSIRO.

How widespread compaction might be needs to be ascertained, it is certainly not evident everywhere on

sands in the region. For example in only three of eight dune/swales investigated in South Australia and

Victoria (Table 7)was the plant available water capacity in dune soils drastically lower than in associated

swales. Restricting root growth to such a shallow zone very much restricts plant available water. On a

sand at Walpeup in Victoria, Walsh (1995) found that the plant available water capacity in the top 1m of

soil was only 23mm, with another 40mm in the next 1m. In this case cereal crops were shown to root to

2m depth. Associated root measurements showed that 80% of cereal roots were in the top 20cm but this

only contained 8% (5mm) of the PAWC.


Table 7 Plant available water capacity (mm) for wheat crops across a paddock toposequence at

different sites in the SE Australian Mallee. Data from Moodie 2010).

Location Dune Mid-slope Swale

Paringa 142 110 144

Loxton 72 118 128

Lameroo 78 179

Ouyen 134 142 240

Natya 134, 75 167

Millewa 71 95

Root growth is typically impeded at resistances of 1MPa and ceases at 5 Mpa (Passioura 2002). High soil

strength restricts root growth, with the effects very much exacerbated in drier soils, thus roots would not

be expected to extend beyond the wetting front in high strength soils. Wheat was shown to penetrate wet

soils with high bulk density (>1.6 kg/m3) at 1m depth in the Victorian Mallee (Incerti and O'Leary 1990).

While inhibited root growth will obviously lead to reduced uptake of water and nutrients and therefore

lower crop productivity, high resistance to root growth can also constrain plant growth independent of the

effects of reduced water and nutrient uptake. High resistance to plant root growth is reflected in smaller

plant shoots due to a reduced number of cells (Passioura 2002).

Wheat, barley and ryegrass had the least root penetration into a compacted soil layer in field experiments,

lower than a range of broad-leafed species (Materechera et al. 1992). Continuous cropping with cereals

such as wheat is thus likely to exacerbate problems with the development of hard pans because cereal

roots might be less likely to produce useful biopores. Root thickness not root density is the key plant

property in relation to ability to penetrate hard soil layers (Clark et al. 2003), and because broad leaf

species have thicker roots (Materechera et al. 1992) these are likely to be more effective in penetrating

compacted soils and be beneficial to following cereal crops.

Soil bulk density can be readily increased by heavy wheeled traffic, especially when soils are wet (Hamza

and Anderson 2005), but it can also occur naturally in sandy soils if they have a particular combination of

fine and coarse sand particle sizes such that the finer particles settle down between the coarse particles.

This can lead to very high bulk density layers regardless of wheeled traffic. Newell (1961) refers to a

“hard pan variant” of a Kattyoong sand in the Mallee, …”characterised by an extremely hard-drying

sand or sandy loam horizon within 12 in of the surface…The pan is 2 to 6 in. thick, soft when moist.” and

describes the soils as having coarse and fine sand, with little silt.

Some of the Mallee sands may thus have a natural tendency to form impenetrable layers just below the

surface. A natural sorting and movement of soil particles can occur such that they become more tightly

packed over time, with fine sands, clays and silts settling further from the soil surface. This can result in


increased bulk density in this zone. Within such zones in sandy soils Fe and Mn oxides, and CaCO3 can

form and cause cementing of the soil particles, resulting in a thin cemented layer of high strength,

independent of a change in bulk density. Such cemented layers typically appear as a thin yellow/red (Fe)

or black (Mn) zones in the soil. An example can be seen in Figure 12, the abrupt colour change perhaps

indicating a natural high strength layer rather than a traffic induced compacted layer.

Figure 9 A sandy soil from Rankins Springs in central western NSW where water has been observed

remaining in soils after crop harvest (photo courtesy of Michael Pfitzner).


Figure 10 A sandy soil profile at Karoonda in the South Austrian mallee, displaying Fe oxide formation

which could result in high penetration resistance to root growth independent of soil bulk density. (image

courtesy Therese McBeath CSIRO).

Crop roots may be inhibited by high bulk density or high soil strength. It should be noted that bulk

density and soil strength are not the same, bulk density reflects the closeness of the packing of soil

particles, and while this influences soil strength, the latter may be increased independent of bulk density

through cemented layers etc which do not increase bulk density. Bulk density is thus not a reliable

measure of the resistance to plant root growth. To ascertain whether bulk density or soil strength are a

limitation to root growth requires measurement of bulk density, soil strength (penetration resistance) and

pore size distribution. With information on all three of these it might be possible to ascribe the relative

contributions of bulk density and strength to compromised root growth. Effective management responses

to compromised root growth can only be formulated with a knowledge of the process one is trying to

tackle and so an untangling of bulk density and soil strength will likely be required.


Soil compaction induced by wheeled traffic is typically apparent at ca 15 cm depth (Holloway and Dexter

1991; Materechera et al. 1992) but can be deeper in sandy soils (Sadras et al. 2005). Although soil

pressures from sheep hooves can be as high or greater than for tractors (Proffitt et al. 1993), the

compaction of soils due to sheep is very much restricted to the surface and is readily penetrated by normal

tyned seeding implement depths (Bell et al. 2011). With the widespread adoption of reduced tillage

systems, the number of machinery passes per crop have decreased in recent years (Llewellyn and

D'Emden 2009). However, this has also been associated with an increase in crop intensity, replacing

fallow and pasture systems, and may mean that the total number of passes by machinery may not have

decreased where pasture phases have been replaced with continuous cropping. Even under minimum

tillage systems it is thought that 60% of the field will still receive wheeled traffic in any given year

(Hamza and Anderson 2005).

While conservation agriculture practices (reduced tillage stubble retention) are known to increase the

conductivity of the soil and storage of soil water, the relative effects of no till and stubble retention may

be different. There is ample evidence that biopores from previous crops increase infiltration of soil water

and soil water content, and that tillage destroys these biopores (Roper et al. 2013). Furthermore, soils of

low organic matter content are likely to have much lower densities of invertebrates such as earthworms,

ants and termites which are important for creating macropores and enable roots to penetrate soils

(Passioura 1991).

Deep ripping to increase rooting depth of crops

Hard pans need to be disrupted to improve root growth, whether the use of disc seeders, which result in

minimal soils disturbance, compared to tyned implements, makes any difference is unclear. Disc

implements may be friendlier to soil biopores but this will be of little value if there are none in the soil.

Impacts of wheeled traffic is also exacerbated by low organic matter content of soils (Hamza and

Anderson 2005), a feature of sandy soils in low rainfall southern Australia. In trials in Western Australia

(Hamza and Anderson 2008), sandy soils were more responsive to deep (>30cm) ripping than adjacent

finer textured soils.

Increased penetration resistance of soils tended to be deeper on sands (ca 30cm) than on finer textured

soils (ca 15 cm) in studies at Loxton and Caliph in South Australia (Sadras et al. 2005). In ripped soils

plants were able to extract more soil water at depth. Grain yield response to ripping was up to 43%, with

responses still evident in the second crop after ripping. The response to ripping was greater on sands than

finer textured soils. Under ripped soils crop transpiration accounted for a greater fraction of ET than in

control soils and thus crop biomass and grain yield were higher. Responses to ripping will be evident

when deep soil water is critical for crop yield. In seasons with regular rainfall responses to ripping may

not be evident because deeper soil water is less important.


Ripped

Control

0 1 2 3 4

0

0.3

0.6

Penetration resistance (MPa)

Dep

th (

m)

Figure 11 Change in penetration resistance of a sandy soil with depth, following deep (0.6m) ripping at

Loxton in South Australia (from Sadras et al. 2005).

Figure 12 Exposure of an impenetrable layer in a sandy soil at Corrigin in Western Australia. The

furrows in the compacted layer are from earlier deep ripping. Photographer Chris Gazey © Western

Australian Agriculture Authority, 2003.

In a summary of deep ripping trials on Eyre Peninsula from 2006-2008, Paterson and Sheppard (2008)

concluded that (i) sandy soils were more responsive to deep ripping than finer textured soils, (b) that

responses did not persist past 2 years, and (iii) responses did not appear to provide an economic return on


the cost of the deep ripping practice. Also on the Eyre Peninsula, Mayfield and Trengove (2007) observed

a wheat growth and yield response to ripping on sandhill tops and slopes but not on the adjacent flats. The

yield response was also matched by an increase in crop N and P uptake.

In Western Australia Tennant and Hall (2001) felt that deep sands had a higher potential for yield

improvement through removal of compacted layers and increased water uptake, than did finer textured or

texture contrast soils.

There is some evidence that increased growth of crops following ripping results from the extraction of

additional soil water which is otherwise unavailable (e.g. Holloway and Dexter 1991; Sadras et al. 2005).

A wheat crop at Loxton on a ripped sand hill soil had 17mm more water available than a crop in adjacent

unripped soil (Sadras et al. 2005). Ripping must thus increase root penetration in soils, giving access to a

greater volume of soil, and soil water if it is available. The legacy of the ripping will depend on the

frequency of soil profile rewetting, and the relative dependence of the crop on that fraction of the soil

water, although the general experience has been that the effects are only apparent for 1-3 years (Hall et al.

1989; Paterson and Sheppard 2008)

Roget et al. summarised earlier work on deep ripping in the SE Mallee as follows

soil compaction occurred and reduced access to water and nutrients, while at the same time

increased water loss through drainage

ripping increased crop water and nutrient uptake and yield

They also highlighted that there remained a large number of questions around this problem, namely

how widespread is compaction in the region?

is it a consequence of management, soil properties or both

how would different soils respond to ripping?

what is the relationship between response to ripping and rainfall?

would ripping improve grain quality?

how would ripping interact with subsoil constraints?

how long will the ripping effects last?

what is the optimum ripping depth?

how does it stack up economically?

Deep ripping breaks up massive soil structure and provides vertical zones of reduced soil strength,

enabling crop roots to penetrate the soil easier. Where impenetrable layers occur in the soil this provides

the opportunity for crops to extract additional soil water and/or nutrients from deeper in the soil profile.

Trials which investigate responses to ripping of soils should include an investigation of the rooting

response of crops, and the associated extraction of water and nutrients. In the absence of such


measurements it is not possible to ascertain whether the deep ripping has been effective in achieving the

desired amelioration, regardless of crop yield responses. In other words, deep ripping trials which only

report yield responses are not very enlightening because one does not know whether there has been any

change in root growth, or water and nutrient uptake.

3.5 Soil amelioration with clay or organic matter

In some cases amelioration of physical and chemical problems of sandy soils can be effected by

increasing the clay content of the soil. This can be achieved using an external source of clay, spreading it

on the soils surface, and possibly incorporating it by spading to ca 30 cm, or, where there is a suitable

layer of clay beneath the sand, by “delving” it up through the soil. The latter by default also includes deep

ripping.

Clay spreading - clay is applied to the surface of sandy soils and incorporated to 10-15 cm

Spading - a technique used to incorporate clay into the sand surface to a depth of 30-40 cm

Delving - using very deep tillage to bring subsurface clay to a sandy soil surface

Incorporating deep tillage along with combinations of clay delving and/or deep placement of organic

includes a raft of changes to the soil-plant system, and can have substantial effects on crop yields (e.g.

Masters and Davenport 2012). However there remains a need to untangle the specific role of some of

these effects so that the use of these practices can be better managed and outcomes made more

predictable. Farmer guidance on clay spreading and delving technology is available in Leonard (2011).

Figure 13 Clay delving (left) and (right) a spading machine for clay incorporation into a sandy

surface soil


There is substantial grey literature on deep ripping, spading and claying, much of it reporting yield

responses but not the underlying causes of yield response. At times this makes it difficult to untangle

some of the possible interactive effects of the treatments and limits the usefulness and transferability of

the information. May (2006) summarised a wide range of case studies trials of clay spreading and delving

from the Eyre Peninsula in South Australia. Addition of clay was thought to decrease water repellency

and wind erosion and increase soil (chemical and physical) fertility but inconsistent results had been

observed by farmers. A summary of the primary observations from the Eyre Peninsula are as follows.

The clay content of “clays” used by farmers for amelioration of sandy soils ranged from 16-59%, greatly

impacting on the efficacy of the clay added. Clays brought to the surface with a high calcium carbonate

content, such as those from eastern Eyre Peninsula, may result in reduced availability of nutrients.

Manganese deficiencies following application of such clays have been reported, and phosphorus

precipitation is also a significant risk under these conditions. If surface soils are sandy the addition of

sodic clays should not represent a significant problems because the salts should still be readily leached.

Where clays are spread on the surface of damp soils significant compaction problems can be created. In

this case deep ripping will also be required. Leaving large quantities of clay on the surface of the soil can

result in surface sealing and poor water infiltration. Incorporation is generally recommended. Clay

delving has the advantage of deep ripping and addition of clay at the same time. Generally it is more cost

effective than clay spreading and incorporation. However, it is very much restricted to soil with a clay

layer 30-80 cm deep, substantially limiting its application in most areas and even then may only be

effective in parts of paddocks. Delving needs to be done when the soil is relatively dry, and well before

crop sowing because major trafficability problems may arise on wet, recently delved soils.

Eldridge and Hughes (2006) provides a draft review of clay spreading experiences in the southern Murray

Mallee of South Australia. Soil analyses from non-wetting and clay spread soils are given in Table 8.

Their summary notes are as follows.

Generally the water repellent sands in their “natural” state, on paddocks that have not been clay spread

had

a clay content between 4 and 6 %,

a pH (CaCl2) 6 to 6.5

a very low carbonate content, <0.34% or nil to slight,

a low cation exchange capacity (CEC), 2.7 to 4.6 meq

soil organic carbon content from 0.57 to 1.13%.

adequate N &P although one showed very low P.

of the 4 samples had less than optimum extractable K (i.e. less than 100 ppm), and all showed

low exchangeable K (<3meq)


low extractable S (<6ppm) with 2 showing very low (<3ppm)

generally adequate trace elements (Cu, Zn and Mn), although one sample was low in Cu and Mn,

and another low in Zn. However two samples had marginal Mn of 5.2 and 6.5 ppm (below 5ppm

Mn is considered low), while one sample showed high Zn with 4.8ppm (cf 0.7ppm) and Mn with

16ppm (cf 5ppm)

acceptable (low) exchangeable sodium percentages (ESP) and electrical conductivity (ECe) and

Cl, indicating no salinity or sodicity problems.

marginal (less than 3ppm) B in 2 samples

a ratio of cations (Ca, Mg, K) to CEC that are acceptable (i.e. about 65% Ca, 15% Mg, and 3%

K).

The paddocks that had been clay spread were found to have

clay contents in the top 10 cm of 6.8% to 22.3%, with most in the range 6 to 10%

pH(CaCl2) between 6.5 and 8.1

carbonate contents of 0.32 to 2.84%, with 6 samples above a critical limit of 0.5% CaCO3.

generally adequate Cu, although 3 samples showed low Cu (less than 0.3ppm).

high / adequate Zn in all except one sample, which showed low Zn of 0.3ppm (cf more than

0.4ppm considered acceptable). Most contained between 1 to 3ppm Zn.

adequate Mn in approximately 50% of the samples, however 3 of the paddocks had very low Mn

levels in the range 2.5 to 2.9ppm, while 3 had marginal about 5 to 6.5ppm.

increases in CEC in the majority of samples (to between 7.5 and 9.5meq), which correspond to

clay contents between 6.8 and 10.7%. One sample from a poorly incorporated area with clay

content of 22% had CEC of 20.82meq.

appreciable increases in Exchangeable Ca, Mg, and Na,

approximately 33% of samples contained less than adequate exchangeable K (ie <0.3meq), while

20% (3 samples) showed low extractable K (ie <100ppm)

some samples showed somewhat elevated level of ESP, but were still below levels that would

cause problems (ie <6). However on the poorly incorporated area of 22% clay the ESP increased

significantly to 27%. This area had ECe of 18.4dS/m, exchangeable Na of 5.63meq and Cl of

2116ppm, indicating a possible salinity and sodicity problem

generally increased B ranging from 0.3 to 3.8, but still well below toxic levels of 15ppm.

Interestingly two showed marginal soil B of 0.3ppm.

On the sandy coastal soils of Western Australia the effects of deep ripping and clay addition were additive

(Hall et al. 2010). The effects of deep ripping alone were very much reduced over time with recompaction

observed within three years of ripping.


One unintended but useful benefit of delving for clay that has been observed is a reduction in frost

damage of crops (Rebbeck et al. 2007). Canopy temperatures were higher in the crops on delved soil than

undelved soil and this was thought to be due to increased soil water storage and therefore increased heat

storage in delved soils. Clay additions or management practices which change the soil surface albedo

could also play a role in soil heat storage and thus susceptibility to frost but since crop leaf area index

would typically be near maximal during the frost sensitive stage of crop growth, there might be

insufficient radiation reaching the ground surface to make much of an impact. How widespread frost

incidence responses might be to delving and in how many seasons it may occur are yet to be ascertained.

Using delving as a reliable management tool to minimise frost may require a better understanding of the

relative effects of soil water content and albedo to the crop energy balance in the region.


Table 8 Analysis of non-wetting soils prior to clay addition (A) or after clay addition (B) in the south Australian Murray Mallee. (from Eldridge and Hughes

2006)

(A) Non-Wetting Clay

%

CaCO3

%

pH

water

pH

CaCl

Ext P

ppm

Ext K

ppm

Ext S

ppm

OC

%

ECe

(est)

dS/m

Exch

Ca meq

Exch

Mg meq

Exch

Na meq

Exch K

meq

CEC

meq

ESP

%

Ext Cu

ppm

Ext Zn

ppm

Ext Mn

ppm

Ext Fe

ppm

Ext B

ppm

Ext Cl

ppm

1 MO1 No clay 3.9 0.34 6.7 6.3 31 88 2.2 0.69 0.6 1.96 0.5 0.03 0.22 2.71 1.1 1 2.6 5.2 45 0.3 3

4 No clay 4.6 sl 7.2 6.5 37 87 4.4 1.13 0.7 3.70 0.7 0.03 0.19 4.6 0.6 0.6 4.8 16.1 50 0.5 12

5 Schwartz No clay 5.8 nil 6.7 6.1 11 102 2.2 0.57 0.6 2.75 0.73 0.03 0.26 3.77 0.8 0.7 0.3 6.5 47 0.5 5

6 No clay 2.94 0.18 6.8 6.1 34 67 5.4 0.71 0.9 1.75 0.43 0.04 0.17 2.39 1.7 0.33 1.32 3.75 43.17 0.2 18

(B) Clayed

Result

1 MO1 Clayed Poor 8.8 2.84 8.6 8 35 232 2.8 0.78 1.4 7.12 1.8 0.05 0.57 9.54 0.5 0.7 3.1 2.7 24 1.1 3

1 S42 Clayed Good 6.8 1.52 8.2 7.5 31 136 3.5 0.81 1.4 6.99 1.34 0.05 0.32 8.7 0.6 0.7 1.4 5.7 21 0.7 4

2 Clayed (Clayey sand) Good 10.7 0.61 8.2 7.7 24 239 2.8 0.58 1.4 5.81 2.68 0.09 0.59 9.17 1 0.7 4.6 6 25 1 4

2 Clayed Poor 14.4 1.82 8.7 8 23 221 3.5 0.46 1.8 6.34 3.1 0.49 0.53 10.46 4.7 0.6 1.9 2.9 24 3.8 7

3 Clay rise 1 Poor 7.8 1.92 8.5 7.8 50 120 4.6 0.73 1.2 5.45 1.79 0.05 0.3 7.59 0.7 0.6 2.5 2.5 18 1.1 4

3 Clay rise 2 OK 8.7 0.32 7.6 7 44 151 4.6 0.75 1.1 3.25 2.47 0.16 0.37 6.25 2.6 0.8 2.9 6.4 23 1.7 7

5 Clayed 250 t/ha & delved 10.6 Mod 8.8 7.6 8 123 2.8 0.48 1.4 5.45 1.8 0.27 0.3 7.8 3.5 0.9 0.3 9.6 56 1.7 17

6 120 t/ha 2.91 0.2 7.1 6.5 31 52 2.5 0.44 0.8 1.62 0.39 0.03 0.13 2.17 1.4 0.25 2.36 3.14 81 0.3 5

7 200 t/ha 5.86 0.38 8.7 7.9 26 114 5.4 0.39 1.2 4.38 1.24 0.18 0.29 6.09 3.0 0.44 1.38 8.2 79 0.8 5

4 250 t/ha Good 8.6 mod 8.2 7.1 29 84 3.2 0.38 1.1 3.30 0.9 0.03 0.2 4.4 0.7 0.6 0.9 11.8 42 0.6 10

6 250 t/ha 5.82 0.26 8 7.2 90 107 3.4 0.54 1.5 3.25 1.27 0.06 0.27 4.85 1.2 0.34 1.51 3.45 83 0.8 5

8 Clayed Good good 7.93 0.28 7.7 7.3 8 149 19.8 0.62 1.7 6.44 1.26 0.15 0.4 8.25 1.8 0.68 0.99 7.87 39 0.9 35

8 Clayed Poor poor 8.86 3 8.3 7.8 29 138 14.5 0.74 2.4 10.69 0.98 *0.24 0.36 *12.27 *1.9 0.13 0.8 7.14 26 0.7 110

9 Irrig Lucerne (Hard Area) 22.3 0.88 8.5 8.1 105 618 142 0.96 18.4 7.63 5.91 *5.63 1.64 *20.8 *27.0 0.55 1.02 15.21 109 3 2116

10 South Dam poor 4.9 0.22 8.2 7.5 13 50 2.5 0.51 1.1 2.75 0.78 0.05 0.13 3.71 1.3 0.14 1.03 5.46 45 0.3 36

* indicates Exch Na, CEC and ESP have been recalculated to account for high Cl present due to no prewashing of samples


3.6 Crop nutrition

The combination of low organic matter and low cation exchange capacity of sandy soils results in low

natural fertility for these soils. The surface layer is often frightfully low in macronutrients and in

subsequent layers nutrients may only be present in trace amounts (Table 9). Bleached soil layers are also

common on sandy soils and these have sometimes been termed “nutrient deserts”.

Table 9 Macronutrients in a sandhill soil profile at Walpeup, Victoria. from Walsh (1995)

Depth (cM0 Total N

(%)

Olsen P

(ug/g)

Available S

(ug/g)

Skene K

(ug/g)

Exchangeable

K (cmol/kg)

0-20 <0.05 5.48 <3 169 0.70

20-40 <0.05 <0.01 <3 150 0.76

40-60 <0.05 <0.01 <3 203 1.00

60-80 <0.05 <0.01 <3 246 1.30

80-100 <0.05 <0.01 <3 292 1.40

100-120 <0.05 <0.01 <3 273 1.60

120-140 <0.05 <0.01 <3 250 1.46

140-160 <0.05 <0.01 <3 290 1.60

160-180 <0.05 <0.01 <3 345 0.78

180-200 <0.05 <0.01 <3 332 0.80

Nitrogen and sulphur

The organic fertility of coarse textured soils is less than adjacent finer textured soils in the same fields.

Total nitrogen concentrations on dune soils are usually much less than 0.1% (Figure 14), and Walsh 1995

measured no change in total soil N (< 0.05%) or available sulphur (<3 ug/g) down to 2m depth in a sand

profile at Walpeup in Victoria (Table 9). Roget and Gupta (1999) noted that while increased nutrition led

to a profitable increase in yield and grain protein, the additional N taken up by crops in the Mallee

exceeded that added in fertiliser, and thus the long term fertility trend would probably be down with

intensive cereal crop rotations. Declining yields on sands could thus be due to declining N fertility with

the removal of pasture/fallow systems. Coventry et al. (1998) suggested that the move away from pasture

phases to continuous cropping would carry with it the risk of further eroding soil organic matter stocks

and reduce the already low soil fertility. The low organic N on the dune soils translates to lower

mineralisation of N in these soils, regardless of rotational crop (Figure 15). Interestingly differences

between the mineralisation potential of the different rotation crops remain >18 months after harvest of the

rotational crop, but this did not translate into differences in the total available N in the top 1m of soil.

Indeed all treatments and landscape positions had high available N.


Figure 14 Total nitrogen (%) in the top 10 cm of dune and swale soils at three sites in north west

Victoria. The soil at the Karawinna site is a sandy across the whole site (From Moodie 2012b).

Figure 15 Mineralisable nitrogen in dune and swale soils at sowing of a second wheat crop in 2012,

following a range of break crops two years previous at Karoonda in the South Australian Mallee. The

toposequence runs up a slope from a clay flat (Swale) to a sandy rise (Dune) . (from McBeath et al.

2013c).

At Karoonda, even after two annual applications of 80 kg N/ha to wheat, the available N to 1m on a sand

(69 kg/ha) was less than half of that on adjacent fine textured soil in the same field (144 kg N/ha, Table


10), and the sand but not the finer textured swale remained responsive to N (Figure 16). In another

sequence of four wheat crops at the same site, available N at sowing (Table 11) was less variable on the

sandy dune (33-71 kg N/ha) than on the associated swale (31 – 167 kg N/ha). After four years of

continuous wheat in a wet year at Karoonda (2010), there was a greater grain yield response to N

application up to 80 kg N/ha on the sands than the flat (Figure 16A), and in a dry year (2012, Figure 16B)

after the seventh consecutive wheat crop, the sand and mid slope but not the swale remained responsive to

N fertiliser.

Figure 16 Crop grain yield response to N fertiliser application for a fifth (A) or seventh (B) consecutive

wheat crop in a toposequence at Karoonda in the South Australian Mallee (from McBeath et al. 2011

and McBeath et al. 2013b).

Table 10 Plant available (mineral) nitrogen (kg/ha) at sowing of a seventh consecutive wheat crop in

2012 after three years of different N input at Karoonda in the South Australian Mallee (from McBeath et

al. 2013b).

N Rate Swale Mid-slope Dune

kg/ha 0-60cm 60-100cm 0-60cm 60-100cm 0-60cm 60-100cm

0 58b 23c 36b 19 36 11b

20 98a 50a 44ab 21 45 24a

80 108a 36b 60a 17 47 22a

A B


Table 11 Plant available (mineral) nitrogen (kg /ha) in the top 1m of soil at sowing for consecutive

wheat crops at Karoonda in the South Australian Mallee. Annual N fertiliser rates applied after soil

sampling are given in parentheses. (data from T McBeath, CSIRO).

Soil

Description

2009

(25kg N)

2010

(7 kgN)

2011

(9 kg N)

2012

(9 kg N)

Swale 33 167 124 101

Mid-slope 38 115 86 65

Dune 35 57 47 68

It would thus appear that crops on sandy soils are constantly N responsive. A tempting possibility is that

mineral N moves downward with soil water on the dune soils, beyond the crop rooting zone, and possibly

laterally, providing additional N and nutrients at the break of slope. The available data are equivocal in

respect to this possibility.

Table 12 Soil nitrate-N (kg N/ha) in a toposequence at Karoonda at sowing of a wheat crop in

2010(from McBeath et al. 2011)

Depth (cm) Dune Mid-slope Swale

0-10 15 29 33

10-20 8 12 38

20-40 11 22 42

40-60 7 10 21

60-80 8 13 16

80-100 7 14 18

These nitrogen data from Karoonda present somewhat of an interpretation conundrum and demonstrate

our inability to be able to effectively predict N dynamics in cropping systems. Further drilling down into

the data might provide some answers but from the summaries which are currently available it is not clear

what is driving the N responses on the sandy soils and whether leaching of NO3-N is occurring. One year

break crops would appear to provide additional available N above that being achieved with continuous

cereals.

Soil S analysis on Mallee sands (Porker and Wheeler 2013a) demonstrated that there was substantial

movement of plant available sulphur below the top 10 cm of soil, the analysis depth from which fertiliser

recommendations were often made. More reliable fertiliser S guidance was provided by deep soil (0-

60cm) analysis. Recent trials on responses of barley to N and S on sandy soils in the South Australian

Mallee (Porker and Wheeler 2013b) indicted that more crops were N than S responsive, and that where


they were S responsive, sulphate of ammonia fed crops yielded more than crops supplied with gypsum or

urea. Furthermore, at Karoonda, highest yields were obtained where trace elements (Zn, Cu and Mn) were

added as well as N, with yields 77% higher than control (no fertiliser) treatments and more than 40%

higher than N (urea) only treatments. In a survey of clayed soils in the southern SA Mallee (Eldridge and

Hughes 2006) available S was low in nearly all soils surveyed, and Walsh 1995) found that the sulphur

concentration in barley shoots grown on sandhill soil at Walpeup was lower than the recommended

critical value, at all of a range of S additions up to 24 kg S/ha.

Walsh (1995) suggested that decreases in crop yields as one moved up a sandhill soil were due to

declining fertility across the dune. Crops were responsive to the combination of both N and P. Organic

carbon, total nitrogen and Olsen P declined as one moved up the dune slope to the crest, although he did

not provide a statistical analysis or correlation between yield and soil fertility. Although Walsh (1995) did

not show a decline in available S across the sand dune he presented substantial evidence that sulfur was

likely to be limiting on the sandhill soils, and was likely to be leached and/or the S applied was not

oxidised.

Phosphorus

In the 2001 audit of nutrient balances in Australian agriculture (Reuter 2001), the low rainfall cropping

region of South Australia was considered at highest risk of phosphorus deficiency. It is generally

considered that much of the phosphorus fertiliser added to soils is adsorbed on to soil particles or

precipitated as insoluble compounds, iron below pH 5 and calcium above pH 8 (Figure 17). Phosphorus

responses appear to have been difficult to predict although McBeath et al. 2013b) found it more profitable

to apply P fertiliser to sand dunes rather than swales at Karoonda.

In studies on 31 acid sandy soil sites in south east South Australia, on average, 28% of phosphorus

fertiliser was leached below the crop root zone in the year of application (Lewis et al. 1981). Leaching

was higher in soils with low organic matter content and lower concentrations of aluminum and iron.

There is thus the possibility of phosphorus leaching from sandy soils in lower rainfall regions as well.

While the phosphorus buffering index in the coarse textured soil was much lower than on the finer

textured swale at the surface, it was slightly higher at 80cm (Table 14). Differences in the relative

distribution of available P with depth in different soils at Karoonda are somewhat equivocal with respect

to downward movement of P (Figure 18).


Figure 17 Fixation of soil P as a function of soil pH. (Adapted from Glendinning 1999)

Table 13 Soil fertility indicators as a function of landscape position and soil type in a single field at

Karoonda, South Australia. (data courtesy of T. McBeath CSIRO).

Soil

Description

Phosphorus

buffering

index

Potassium

(Colwell)

(mg/kg)

Sulphur

KCl-40

(mg/kg)

Cation exchange

capacity

(meq/100g)

Swale 61 457 3.9 14.7

Swale 43 381 4.4 11.0

Mid-slope 21 266 4.2 5.8

Mid-slope 17 227 3.4 4.4

Mid-slope 14 149 3.0 3.2

Crest 12 114 2.2 2.8

Dune 9 122 1.8 2.2

Dune 9 116 1.7 2.3

Dune 10 111 1.7 2.4


-80

-70

-60

-50

-40

-30

-20

-10

0

0 10 20 30 40 50 60

Dep

th (

cm)

Relative proportion of Colwell P - %

Swale Mid-slope Dune

Zone Colwell P (total)Swale 70Mid-slope 40Hill 52

Table 14 Variation in Phosphorus buffering index with depth as a function of landscape position and

soil type in a single field at Karoonda, South Australia (data courtesy S. Mason, University of Adelaide).

Depth Swale Mid-slope Hill

0-10cm 28 7 6

10-20cm 46 2 6

20-40cm 105 12 9

40-60cm 91 34 28

60-80cm 64 88 71

Figure 18 Variation in proportion of available Phosphorus with depth as a function of landscape

position and soil type in a single field at Karoonda, South Australia (data courtesy of S. Mason,

University of Adelaide).

Extensive research into fluid fertilisers on the Eyre Peninsula, especially P and Zn, have shown that they

are preferable on soils with a pH >8.5 and a calcium carbonate content >10%. These conditions are

unlikely to be met for the primary sandy soils of interest, although there are strongly calcareous deep

sands on parts of the Eyre Peninsula where fluid fertilisers provide significant yield advantages over

granular fertilisers (Wheeler et al. 2003) .

Potassium

Potassium deficiency has been documented on acid sands in Western Australia (Brennan et al. 2004). The

problem primarily stems from a combination of parent materials with low K and a leaching environment.

I have not found any reports of K deficiency on sandy soils in the target region for this report.


Micronutrients

Zinc deficiency is well known in sandy soils across the southern Australian cropping zone (Alloway et al.

2008), with 80% of South Australia’s agricultural lands potentially Zinc responsive (Reuter 1988 tech

report). Zinc deficiency is likely on a wide range of alkaline soil types, including the calcareous sands and

sandy loams of the region. The switch from superphosphate to high analysis fertilisers has reduced the

fortuitous zinc application with earlier phosphates (ca 0.04% zinc, Alloway et al. 2008).

A more recent analysis based on Australian soil orders (Norton 2013) indicated that Calcarosols,

Dermosols and (highly alkaline) Vertosols were the highest risk of zinc deficiency (Table 15). In

particular, Zn deficiency was considered most likely on alkaline sands with high phosphorus availability.

Where sands have a poor capacity to buffer added P, the risk of Zn deficiency might therefore be

increased if Zn3(PO4)2 mineral (hopeite) or scholzite (CaZn2(PO4)2) are precipitated. Conditions

conducive to this would be a soil available P concentration of ca ≥0.1 mM and a pH >7.5. Calcarosols

and alkaline Vertosols also considered to be at high risk of manganese deficiency. Copper deficiency has

been observed on sandy soils in the South Australian Murray Mallee o (Braunack-Mayer 2000). King

(1974) reported that copper deficiency was common in wheat grown on deep siliceous sands, calcareous

sand, sand over clay, and soils with ironstone granules in the Eyre Peninsula and Murray Mallee of

South Australia, with Cu fertiliser applications recommended every five years.

Table 15 Risk of micronutrient deficiency for Australian soil orders. From Norton (2013).

Large differences in the efficiency of use of zinc has been observed between cereal cultivars (Graham et

al. 1992; Holloway et al. 2010) and may provide a useful adjunct for infertile sandy soils, and indeed for

other micronutrients (Ma et al. 2009). However, nutrient efficient cultivars cannot provide a solution to

absolute deficiencies which can only be addressed through nutrient addition.


Addition of acid to lower the pH of Mallee sands did not increase the uptake of micronutrients by barley

grown in pots containing soils from each 20cm layer to 2m depth (Walsh 1995), therefore one might

anticipate an absolute rather than pH induced deficiency of micronutrients in these soils.

Boron toxicity is often considered a significant problem in many Mallee soils (Cartwright et al. 1986;

Nuttall et al. 2003a; Nuttall et al. 2003b), however on soils of very low clay content (<5%) boron

deficiency is more probable. In Western Australia B deficiency has been identified on siliceous sands

(Wong et al. 2005). There is a relatively narrow range between deficient and toxic concentrations of B in

soils.

Deep placement of nutrients

Reduced tillage systems tend to be associated with the targeted placement of fertilisers close to the seed,

either beside or under the seed. Compared to previous cultivation systems this can result in stratification

of nutrients in near surface zones (Ma et al. 2009). Since water can move freely down the profile of sandy

soils it can also take mobile nutrients such as N, S and K with it, beyond the reach of crop roots. This can

reduce the residual value of fertilisers and mineralised nutrients.

In a review of deep placement of nutrients topic Ma et al. (2009) concluded that the greatest responses

were to be found on infertile sandy soils in low rainfall regions. The benefits were thought to primarily

arise from having subsoil nutrients available when the surface soil is dry from which plants are generally

unable to extract nutrients. The authors considered that deep placed nutrients should have residual value

for many subsequent years, although there were few examples of this given.

There have been a substantial number of trials of deep placed nutrients, particularly on the Eyre Peninsula

in South Australia. Many of these trials have been on texture contrast soils, with relatively shallow (<50

cm) sands. On a siliceous sand over clay (35cm) at Wharminda, the placement of fluid nutrients (H3PO4,

Urea, ZnSO4, MnSO4, CUSO4, mono-ammonium phosphate, and NH4NO3) to 40cm gave consistently

high yields across four years, and similar results were observed on sandy soils elsewhere across the region

(Doudle and Wilhelm 2002). Similar nutrients placed only near surface were not as effective, nor was

deep ripping alone.

Root growth of crops may be compromised in soils zones with a lack of zinc (Nable and Webb 1993)

such that while the shoot may not be Zn compromised, water uptake will be because roots will not grow

in Zn deficient soil zones. Thus surface applied zinc may not be as effective as deep placed zinc which

might assist in extracting unused water from soil profiles. When surface soils are dry, zinc is unable to

diffuse toward plant roots (McBeath et al. 2012).


Experiments with deep placement of nutrients across southern Australia has generally resulted in

substantial crop yield improvements (Ma et al. 2009), often with residual value (Wilhelm 2005). The

responses have typically been greater on sandy than finer textured soils (Ma et al. 2009), and particularly

on sands at least 250mm deep (Wilhelm 2005). The South Australian government is currently investing in

such soil enhancement protocols in a bid to improve productivity on sandy soils and may be able to

provide effective guidelines in the medium term (see http://www.pir.sa.gov.au/newhorizons).

Nutrition summary

Soil fertility is inevitably low in the sandy soils of low rainfall SE Australia and will require ongoing,

active management. However, before this can be efficiently achieved there is a need to be able to develop

some predictive capacity in terms of which particular nutrients are likely to be limiting in different sandy

soil types, what forms the nutrients should be added in, and which crops or crop sequences may increase

the efficiency of nutrient use. The importance of leaching of nutrients, not just N, needs to be considered,

along with further investigation of trace element deficiencies, and the likely importance and availability

of nutrients below the A1 soil horizon. Because of the low cation exchange capacity of these soils, the

possibility of interactions between nutrients reducing their availability should also be explored.

3.7 Soil carbon and biological fertility

As indicated in Section 2, coarse textured soils have a poor capacity to protect soil organic matter from

breakdown and thus tend to have lower organic carbon stocks and lower soil biological activity. These

factors reduce nutrient availability, decrease aggregate stability and reduce the ability of the soil to hold

water. In the absence of substantial addition of clays these problems cannot be ameliorated in sandy soils

but they can be mitigated to some extent. Differences between soil carbon density between sands and

finer textured soils within single fields are illustrated in Figure 19 which shows that organic C density in

interdune (swale) soils can be more than double that of sandy dunes in the Victorian Mallee.

Systems with higher plant residue inputs and reduced tillage generally have greater C stocks than parallel

systems with lower residue inputs and greater tillage. Thus soil C stocks can be increased through reduced

tillage and stubble retention relative to cultivated systems with stubble removal. Evidence to support this

is often confused because the C stock in many Australian agricultural soils have not yet reached the usual

lower equilibrium which occurs after initial land clearing, and consequently the soil C stock on many

agricultural soils are decreasing regardless of management (Sanderman et al. 2010). However, in a study

at Waikerie in the Victorian Mallee the data of Gupta et al. (2008) demonstrate that soil C stocks were

maintained after eight years under increased productivity, lower tillage systems, while comparative tilled

http://www.pir.sa.gov.au/newhorizons


1.2

1.0

0.8

0.6

0.4

0.2

0

swale Chinkapook

swale Cowangie

dune Chinkapookdune Karawinnadune Cowangie

Soil

org

anic

C (

%)

and lower productivity systems showed a greater decline in soil C stock. Thus while soil C stock may not

always increase in absolute terms with conservation cropping systems, they will likely mitigate further C

loss from these soils. In some cases soil C stocks should be able to be increased, resulting in physical,

biological and chemical fertility benefits on these soils.

Figure 19 Organic carbon (%) in the top 10 cm of dune and swale soils at three sites in north west

Victoria. The Karawinna site is a sandy across the whole field. Data from Moodie (2012b).

In studies on soil microbial activity (Roget and Gupta 1999) in the Mallee it was found that overall

activity was low, due to low organic matter and low rainfall. It was considered lower than in other soils

across Australia. Systems with increased crop residue inputs have been shown to have larger microbial

populations, resulting in competitive inhibition of pathogens and increased predatory and parasitic

activity (Roper and Gupta 1995). It has also recently been demonstrated (Evans et al. 2011) that ants and

termites play a vital role in increasing soil water and fertility in arid environments, resulting in substantial

increases in wheat yield above that with depressed populations of these invertebrates. Practices which

reduce their number are likely to decrease water and N availability in soils, and crop yields, in low

rainfall environments.

3.8 Pests and diseases on sandy soils

Impacts of soil borne diseases can be significant in coarse sandy soils because plants need larger root

systems to extract moisture and nutrients. These soils also often have poor soil biology and thus reduced

competition with pathogens. These soils would also favour pathogens that prefer drier conditions e.g.

Rhizoctonia root rot, crown rot, common root rot. As a general rule nematodes also prefer soils with

relatively large pore spaces, as they cannot move well in poorly structured clay soil, so Cereal Cyst

Nematode and Pratylenchus nematodes could also thrive in these soils. Because sandy soils have lower

organic fertility and fewer microsites to protect soil biota, they may have a lower capacity to suppress

pathogens and other pests, this may be exacerbated by low water holding capacity because periods of


microbial activity over the summer are important for reducing pathogens such as Rhizoctonia (Figure 20)

and probably other fungal pathogens (rots). Coventry et al. 1998) suggested take-all might be a significant

problem on sandy soils on the Eyre Peninsula because of associated poor root growth of crops.

Figure 20 Change in Rhizoctonia (R. solani AG8) DNA density in soil under different crop rotations

over the summer fallow period at Waikerie in the Murray Mallee. Clouds indicate rain events and arrows

tillage events (from Gupta et al. 2010).

Figure 21 Rhizoctonia solani (AG8) inocula concentrations under a range of crops (following wheat)

across the toposequence at Karoonda (from Gupta et al. 2012b).


Evidence from Karoonda (Figure 21) would however indicate that Rhizoctonia inocula concentrations are

lower on sand hill than swale clay soils and so the potential susceptibility of sands to pests and diseases as

described above may not eventuate, but instead other factors may play over riding roles in controlling the

relative intensity of Rhizoctonia propagules on sands and clay soils. While rainfall events may contribute

to short-term reductions in Rhizoctonia inocula, Figure 21 illustrates that the most valuable management

tool in Rhizoctonia control is rotation with non-cereal crops.

This dataset clearly shows that rotation with grass/cereal free breaks is key to reducing rhizoctonia

inocula, and that the coarser textured soils on the dunes and slopes have lower disease loads than the finer

textured soils on the swale. Grass free rotations of Brassicas, chickpea, field pea, vetch, medic and fallow

were shown to increase what yielded by 9 -47% compared to cereals or other grassy phases (Gupta et al.

2013). The problem with this is that non-cereal crops are rarely grown in this region ( see Section 5)

Crops with low nutrient supply tend to suffer more from Rhizoctonia symptoms because of the root

pruning effect of the fungus, and this is why good nutrition can reduce the severity of the disease. This

may illustrate why summer weed control, either complete or partial, has been shown to decrease

Rhizoctonia inoculum in soils and infection of subsequent barley, and increase grain yield of barley at

Karoonda (Gupta et al. 2013). Weeds may reduce both mineral N supply to the subsequent crop and also

the amount of moisture available for microbes, reducing disease suppression. A combination of

measurement and modelling of a wheat-barley rotation on a sand at Karoonda indicated that, without

summer weed control, Rhizoctonia may reduce grain yield of barley by up to 40%, and with summer

weed control the contribution of Rhizoctonia to yield loss could be up to 27% (Gupta et al. 2013). The

impact of Rhizoctonia on cereals is greater for slow growing roots, therefore in dry years with compacted

layers rhizoctonia is likely to be a greater problem.

3.9 Weeds and herbicides

I have identified little research on weed control and herbicide management specifically on sandy soils

within the low rainfall SE Australia which might spotlight particular issues on sandy soils. This section is

thus restricted to observations of consultants in the field which have been recounted and some general

issues which should be considered. The primary concerns specific to sandy soil is crop damage from

movement of pre-emergent herbicides into seed rows or the root zone of emerging crops, water repellency

causing staggered germination of weeds, and potential leaching of soluble, persistent herbicides.

For highly soluble herbicides, such as those in Group B, herbicide translocation across the soil can occur

through movement of water over the surface (Blackwell 2000), or just below the soil surface. Such water


flow is more common in coarser textured soils and is a feature of non-wetting soils. Furthermore, when

sandy soils are dry, herbicide laden soils can be easily thrown from the inter-row across to the seed row,

again transferring herbicide to the crop row, rather than the inter-rows. These problems are not restricted

to Group B herbicides and have been observed in both cereal and pulse crops in South Australia and

NSW (Jason Sabeeney, Barry Haskins pers comm.). Leaching of soluble herbicides to >50cm has been

observed on loams in the Victorian Mallee (Stork 1995) and can readily occur on sandy soils (Ying and

Williams 2000), especially those displaying preferential water flow (McGrath et al. 2010) as observed on

non-wetting sands in Western Australia (Blackwell 2000). It is not known if this would result in problems

for sensitive crops species because of residual herbicide at depth, but one might anticipate some

degradation of the herbicide in moist environments.

Where recropping intervals for herbicides carry a minimum rainfall requirement, this may take some time

to be met in lower rainfall environments and time between recropping intervals may thus exceed 2 years

in some cases. Herbicide residues will also degrade more slowly in dry soils (Hollaway et al. 2006) and

soils with low organic matter, although conversely higher temperatures and low clay content increase the

rate of degradation. Residual herbicides can also make crops more susceptible to root diseases such as

Rhizoctonia (Rovira and McDonald 1986).

Many of the Group B herbicides degrade more slowly in alkaline soils (Hollaway et al. 2005). Legumes

and oilseeds are most vulnerable to Group B (sulfonylureas), especially lentil and medic. Barley can also

be sensitive to some sulfonylureas. A herbicide tolerant variant of barrel medic is available (Peck and

Howie 2012), in addition to being a good adaptation to these low rainfall farming systems, this could also

be a valuable research tool for examining the possible extent and impact of herbicide residues on these

sandy soils, including the possibility of residues at depth.

4 Water use efficiency as a measure of productivity

Figure 22 clearly shows that the demand for water in the region (pan evaporation) greatly exceeds the

supply of water, hence water is often the key limitation to crop growth rather than radiation. Efforts to use

all the water which is available as efficiently as possible is a primary objective for farmers. Figure 23

shows an often used framework for assessing water use efficiency. In this seasonal water use

(evapotranspiration) is split into direct evaporation of water from the soil (the X (horizontal) axis

intercept) and crop transpiration, the area under the sloping line. The slope of the line represents the

“transpiration efficiency”, the ratio of shoot dry matter produced per unit of crop transpiration (crop water

use). Transpiration efficiencies are a fairly conservative parameter, set at the leaf level (Cowan 1984) and

are unlikely to vary significantly within a site since the primary influence is through the atmospheric

demand for water (the vapour pressure deficit). Therefore the main opportunity for increasing crop


ET (mm water)Evaporation Transpiration



Sho

ot

dry

mat

ter

(or

grai

n y

ield

)

Reduced evaporative losses would be diverted to transpiration (DM production )

Opportunities for increasing DM/T are generally much smaller than for increasing T

For GY/T can be through changes in harvest index

At some point an upper limit will be defined by radiation interception

(A) (B) (C)

0

10

20

30

40

50

60

70

1 5 9 13 17 21 25 29 33 37 41 45 49

Average weeklypan evaporation

Averageweekly rainfall

Ave

rage

wee

kly

rain

fall

or

pan

eva

po

rati

on

(m

m)

Week of the year

production through the water balance is either through increasing total water use, and/or decreasing the

direct soil evaporation term (X intercept). Where water use efficiency is expressed as grain yield per mm

water transpired (e.g. Figure 23), the slope of the line should not be interpreted as a transpiration

efficiency, but a product of transpiration efficiency for dry matter, flowering capacity and flowering

success, grain development and effects of pests (especially in experimental plots), diseases and frost on

grain weight, and finally, the effectiveness of grain harvest. Shattering losses, particularly for broadleaf

crops, can have a significant impact on apparent crop water use efficiency where grain yield is plotted on

the Y axis. To avoid misleading interpretations it is thus better to examine water use efficiency in terms of

dry matter production, and in this case the X axis intercept equates directly to bare soil evaporation. Grain

yield (harvest index) efficiency analysis is best conducted after an independent water use efficiency

assessment

Figure 22 Average weekly open pan evaporation and average weekly rainfall totals for Walpeup, in the

Victorian Mallee.

Figure 23 Relationship between (A) evaporation from soil, plant transpiration and seasonal dry matter

(DM) production, and (B) transpiration efficiency and dry matter production or grain yield (GY), and (C)

introduction of radiation limited growth at luxury water supply.


In studies at Karoonda in 2009 (Whitbread et al. 2010) dry matter production of wheat was lowest on the

sandy dune and highest on the mid slope. This was interpreted as a higher efficiency per mm of water

transpired. Using the above framework we might equate it to either less total water used, a lesser fraction

of the total evapotranspiration was transpired, and/or the harvest indices differed. Given the large

difference in dry matter production between the dune and the mid-slope (Table 16) total water use and/or

the fraction as transpiration were likely to have been lower on the dune.

Table 16 Shoot dry matter and grain yield of wheat as a function of landscape position and soil type in

a single field at Karoonda, South Australia (from Whitbread et al. 2010)

Position Shoot dry matter

Sept. 23 (kg/ha)

Grain yield

(kg/ha)

Harvest index

Dune 2300 800 0.35

Mid-slope 3800 1500 0.39

Swale 2900 1000 0.34

When examining water use efficiency the difference in the efficiency of water use and actual water use

needs to be carefully considered if we are to understand where the opportunities for increasing both are to

be found. Figure 8 is quite telling in this respect, indicating that there is much unused water under crops

on the sandy dunes, it implies that an increase in transpiration might be achieved through an increase in

total water use. Evidence for increasing transpiration as a fraction of total water use is not yet evident but

may be a real possibility. A comparison of crop harvest indices on the different soils within the topo

sequence within the Karoonda dataset might also be quite illuminating in untangling the few components

of Figure 23. Walsh (1995) felt that there was a need to better define water limited potential for the

sandhill soils to better indicate how to close to potential water limited yields the crops are.

In terms of the water balance, the possibility of lateral water movement from the dune crests and

discharge to the mid slope, or even run off should not be discounted in the water balance in low rainfall

SA Australia. The high transmissivity of the sandy soils would readily permit deep percolation and lateral

movement of water, and perhaps nutrients, which could sponsor the additional growth often indicated on

the mid-slope (e.g. Table 16). In this case the water use and efficiency figures would need to be adjusted

for the additional water available to crops in this position. Such possibilities should not be dismissed as

irrelevant, but need to be understood if we are to provide reliable predictive capacity for growers in this

environment. Water movement in sands is very different to that of finer textured soils, with gravity

probably playing a greater role than capillary action. Deep drainage on Mallee soils has been well

documented (Diaz-Ambrona et al. 2005; O'Connell et al. 2003; O'Connell et al. 1995; Sadras et al. 2003).

Infiltration and drainage rates of >200mm per hour have been recorded for Mallee sands (Walsh 1995),

rates at least double those of the interdune soil. A simulated rainfall equivalent to 125mm of water had


moved to 2m depth in 4 days, and all of it had moved below 2m one week after application on a Mallee

sand (Walsh 1995). This is one of the key differences between sands and clays, water penetrates more

quickly and more deeply, necessitating deeper rooting if crops are to be able to retrieve the soil water.

The speed at which water moves down the profile is directly related to soil texture, consequently crops in

finer textured sols do not need to root as deeply as those on coarse textured soils to encounter the same

amount of water. Given that Figure 8 indicates a lower rooting depth for crops on the sands, these crops

must have a disproportionately lower total water supply, thus promoting deeper root growth on the sands

is critical to improving crop productivity.

5 System effects

It is unclear whether cereal crops are more or less responsive to break crops on sands compared to the

other soils in the toposequence. Although Figure 24 could be interpreted as sands being less sensitive to

break crop effects, without knowledge of the proportional yield increases on the different soil types the

relative responses are uncertain. This should be possible to ascertain from the data underlying Figure 24.

Gupta et al. (2012a) concluded that “The key benefits of the medic-based pasture and grain legume break

crops were increased soil N from fixed N in residues, whereas the benefits from mustard and canola were

from a reduction in Rhizoctonia solani AG8 inoculum while canola, mustard and rye all increased

microbial activity and N mineralisation potential. The reduction in Rhizoctonia solani inoculum and

mycorrhizal fungi after canola and mustard lasted for one following wheat crop only whereas nutrient

related benefits may extend for more than one following cereal crop”. Crop rotation is the key element of

sustainable production from a biophysical standpoint, however, this has probably been the Achilles heel

of farming systems on sandy soils in low rainfall SA Australia. Although there has been great progress,

there is a continuing challenge in obtaining reliable production and erosion protection with non-cereal

crops on sandy soils in low rainfall environments.


Figure 24 Break crop effects (t/ha) reported by farmers in the Victorian Mallee following canola or

pulse crops on dunes (sand), mid-slope (loam) or heavy (swale) soils.

In experiments on a series of sandy soils in the Victorian Mallee (Walsh 1995), wheat yields at one site

were consistently low and found to be unresponsive to management (rotations). This was attributed to

past erosion events decimating soil fertility, whereas as other sand hill soils which had adequate fertility

were very responsive to rotation with legumes. Even low yielding legume rotational crops have been

observed to provide good rotational benefits to following cereals (Coventry et al. 1998) but this alone

does not counter the higher costs and risks of growing legumes in the low rainfall environment. Rotation

sequence had no impact on soil water at harvest of wheat on a sand at Walpeup, suggesting that rotational

crop effects did not include influence on rooting depth or water extraction (Walsh 1995).

Although it has been repeatedly demonstrated that non-cereal rotations are of great benefit to farming

systems, the examples given above appear somewhat academic given the fact that less than 10% of the

cropping area in the SA-Vic Mallee was sown to non-cereal crops in the 2010 calendar year (Table 17).

While pasture/fallow/cereal crops were the backbone of mallee agriculture for many years, there has

always been problems with establishment of pasture legumes on sandy soils of the region (Walsh 1995).

The major challenge is thus to develop suitable broadleaf crop types and technologies for low rainfall

sandy soils, a challenge which has remained somewhat stagnant for a long period of time despite previous

investments. The reasons for the lack of progress in solution of this problem would be worthy of a

thorough review in its own right.


Table 17 Percentage of cropping area sown to cereals, grain legumes or canola in the 2011

agricultural census

Region Cereals Legumes Canola

Victorian Mallee 90 6 3

Eyre Peninsula 90 4 5

SA Murray Lands 92 3 4

6 Summary and Conclusions

The weight of evidence from low rainfall Se Australia is that productivity on sandy soils is well below

potential and that opportunities for improving productivity in the region are likely to be greater on sands

than finer textured soils.

There has been a shift in the region toward more intensive cereal cropping, primarily at the expense of

fallow and pastures, thus practices which had previously accumulated organic nutrients and water have

been replaced by fertilisers and intensive cropping. While contemporary minimum tillage systems might

result in less wheeled traffic than previous systems which used cultivation to control weeds (Cooke et al.

1989), the higher frequency of cropping may mean that there are as many machinery passes as previous

but without the disruptive tillage. Compaction on sandy soils can occur under drier conditions than for

finer textured soils. The notion that reduced tillage systems have led to less total wheeled traffic over

fields needs to be verified.

Root growth in compacted soils is reduced, this will be a factor when water is limiting but less so when

rainfall is sufficient for growth, as opposed to stored soil water. In most years soils do not wet to field

capacity in the region, and problems of high penetration resistance will thus be exacerbated in drier years

and drier environments. The possibility that rotations which include broad-leaf crop species with thick

roots may assist in reducing the impact of hard pans is worthy of investigation because it is root thickness

rather than density which seems to be the important attribute.

Sandy soils in the region may be more responsive to deep ripping than finer textured soils. Deep tillage,

with combinations of nutrients, organic matter or clay additions with spading could play a role in

ameliorating some of the constraints on sandy soils but are not sufficiently robust at present to be widely

recommended. Such approaches will attack the problem of poor root growth and unused water on a

number of fronts. The use of clay as an ameliorant will most likely be restricted to systems with suitable

in situ sub-surface clays, or clays available within the treatment paddock. However, this is likely to be

restricted in their application to very particular soils profiles and situations. This is a focus of the SA State


Government “New Horizons” imitative which could be usefully augmented with some additional targeted

science

The potential for drainage and leaching beyond the root zone of crops is very high on these sandy soils.

The coarse texture allows rapid gravitational pull on soil water. Measurement of leaching is somewhat

time consuming, but it can be readily modelled and this should be done, and a simple tool produced

which can be used to identify when leaching occurs on sandy soils across the region in response to

rainfall. This information can then be used to assist in nutrient budgeting, identifying risks of nutrient

deficiency and ways to improve nutrient management. Strategic soil coring and analysis could be used to

confirm the quantities of nutrients leached across the region.

Improving root development on sandy soils is key, not just to increase water extraction, but because

susceptibility to root damage from pathogens and pests and herbicide residues can interact to reduce

nutrient and water uptake, exacerbating problems of low water holding capacity in the near surface.

Cereals are more susceptible to the effects of compaction on root growth than a range of broad leaf

species.

The primary challenges on coarse textured soils in low rainfall SE Australia are thus:

ensuring that crops grown have deep rooting capacity and deep rooting opportunity

ensure that nutrients are accessible within the crop rooting zone

that crop rotations include more regular broad leaf species

the movement of water and nutrients down the soil profile are understood to the extent that they

can be predicted

the extent of non-wetting and high soil resistance to root growth across the region are better

defined

the specific causes of high soil resistance to root growth are identified

to increase soil organic matter

For each of these recommendations it is important that research questions are carefully framed, and

relevant material thoroughly examined, prior to any experimental work being planned. Many of the

questions can be answered with specifically targeted research, rather than large scale programs

incorporating many treatments and few measurements. This document provides a background not a plan

for action. Smart investment would include a more thorough analysis of existing research and research

data, before designing particular experiments in solution of the considerable problems of coarse textured

soils. The opportunities are significant but will only be realised through the prosecution of experiments

based on specific, well informed, clearly framed hypotheses.


7 References

Alloway B, Graham R, Stacey S (2008) Micronutrient Deficiencies in Australian Field Crops. In

'Micronutrient Deficiencies in Global Crop Production'. (Ed. B Alloway) pp. 63-92. (Springer

Netherlands)

Anon (2011a) Wind erosion susceptibility mapping. Technical Bulletin #24. In. (Mallee Catchment

Management Authority: Mildura)

Anon (2011b) Assessing wind erosion threat in the Mallee region. Technical Bulletin #37. In. d. (Mallee

Catchment Management Authority: Mildura)

Anon (2013a) Assessing the potential for break crops to improve soil health in the mallee. In. 5. (Mallee

Catchment Management Authority: Mildura)

Anon (2013b) Improving canola establishment to reduce wind erosion,Technical Bulletin #34. In. 4.

(Mallee Catchment Management Authority: Mildura)

Bell LW, Kirkegaard JA, Swan A, Hunt JR, Huth NI, Fettell NA (2011) Impacts of soil damage by

grazing livestock on crop productivity. Soil and Tillage Research 113, 19-29.

Bennell MR, Leys JF, Cleugh HA (2007) Sandblasting damage of narrow-leaf lupin (Lupinus

angustifolius L.): a field wind tunnel simulation. Soil Research 45, 119-128.

Blackwell P, Hagan J, Davies S, Bakker P, Hall D, Roper M, Ward P (2014) Smart no-till furrow sowing

opportunities to optimise whole-farm profit on non-wetting soil. In 'GRDC Crop Updates'. 6pp.

(DAF Western Australia: Perth)

Blackwell PS (2000) Management of water repellency in Australia, and risks associated with preferential

flow, pesticide concentration and leaching. Journal of Hydrology 231–232, 384-395.

Brady NC, Weil RR (1999) 'The nature and properties of soils.' (Prentice Hall: Upper Saddle River, New

Jersey)

Braunack-Mayer E (2000) Copper deficiency in cereals: Where is it and what does it look like?

Australian Grain 10, 8-10.

Brennan RF, Bolland MDA, Bowden JW (2004) Potassium deficiency, and molybdenum deficiency and

aluminium toxicity due to soil acidification, have become problems for cropping sandy soils in

south-western Australia. Australian Journal of Experimental Agriculture 44, 1031-1039.

Cann MA (2000) Clay spreading on water repellent sands in the south east of South Australia—

promoting sustainable agriculture. Journal of Hydrology 231–232, 333-341.

Cartwright B, Zarcinas B, Spouncer L (1986) Boron toxicty in South Australian barley crops. Australian

Journal of Agricultural Research 37, 351-9.

Clark LJ, Whalley WR, Barraclough PB (2003) How do roots penetrate strong soil? Plant and Soil 255,

93-104.

Clough A (2012) 'Assessing the potential for break crops to improve soil health in the Mallee.' Mallee

catchment Management Authority, Mildura.

Cooke A, MacLennan H, Erlandson S (1989) Arable farming systems. In 'Mallee Ecosystems'. (Eds I

Noble and J Bradstock) pp. 318-328. (CSIRO: Melbourne)

Coventry DC, Holloway RE, Cummins JA (1998) Farming fragile environments: low rainfall and

difficult soils in South Australia. In 'Proc. 9th Australian Agronomy Conference'. Wagga Wagga

p. 12. (Australian Society Agronomy)

Cowan I (1984) Carbon and water economy in higher plants. In 'Control of crop productivity'. (Ed. C

Pearson) pp. 13-32. (Academic Press: Sydney)

Diaz-Ambrona CGH, O'Leary GJ, Sadras VO, O'Connell MG, Connor DJ (2005) Environmental risk

analysis of farming systems in a semi-arid environment: effect of rotations and management

practices on deep drainage. Field Crops Research 94, 257.

Doudle S, Wilhelm N (2002) Subsoil nutrition - what kind works where and how deep does it need to be?

In 'Eyre Peninsula Farming Systems Summary 2002'. (Eds S Doudle and et al.) pp. 115-119.

(South Australian Research and Development Institute: Minnipa)

Eldridge R, Hughes B (2006) 'Workshop notes, southern mallee draft.' Primary Industries and Resources

South Australia.

Evans TA, Dawes TZ, Ward PR, Lo N (2011) Ants and termites increase crop yield in a dry climate. Nat

Commun 2, 262.

Glendinning J (1999) 'Australian soil fertility manual.' (CSIRO Publishing: Collingwood)


Graham R, Ascher J, Hynes S (1992) Selecting zinc-efficient cereal genotypes for soils of low zinc status.

Plant and Soil 146, 241-250.

Gupta V, Roget D, Davoren C, Llewellyn R, Whitbread A (2008) Farming system impacts on microbial

activity and soil organic matter dynamics in southern Australian Mallee soils. In 'Global Issues

Paddock Action, Proceedings of th 14th Australian Agronomy Conference'. Adelaide. (Ed. M

Unkovich). (Australian Society of Agronomy)

Gupta V, McKay A, Smith D, Cook A, Kirkegaard J, Ophel-Keller K, Roget D (2010) Temporal

dynamics of Rhizoctonia solani AG8 inoculum in Australian soils. In 'Proceedings of the sixth

Australian soilborne disease symposium'. (Ed. G Stirling) p. 51

Gupta V, llewellyn R, McBeath T, Kroker S, Davoren B, McKay A, Ophel-Keller K, Whitbread A

(2012a) Break crops for disease and nutrient management in intensive cereal cropping. In

'Proceedings of 16th Australian Agronomy Conference'. (Ed. I Yunusa). (Armidale)

Gupta V, Llewellyn R, McBeath T, Kroker S, Davoren D, McKay A, Ophel-Keller K, Whitbread A

(2012b) Soil biology and Rhizoctonia disease management update - Break crop experiments at

Karoonda. In 'Mallee Sustainable Farming Results Compendium 2011'. (Mallee Sustinable

Farming Inc: Mildura)

Gupta V, Kroker S, Davoren B, McBeath T, McKay A, Ophel-Keller K, Llewellyn R, Roget D (2013)

Summer weed control benefits Rhizoctonia disease management in cereal crops. In 'Research

Compendium 2012' pp. 5. (Mallee Sustainable Farming Project)

Hall AJ, Connor DJ, Whitfield DM (1989) Contribution of pre-anthesis assimilates to grain-filling in

irrigated and water-stressed sunflower crops I. Estimates using labelled carbon. Field Crops

Research 20, 95-112.

Hall DJM, Jones HR, Crabtree WL, Daniels TL (2010) Claying and deep ripping can increase crop yields

and profits on water repellent sands with marginal fertility in southern Western Australia. Soil

Research 48, 178-187.

Hall J, Maschmedt D, Billing B (2009) 'The soils of southern South Australia.' (Department of Water,

Land and Biodiversity Conservation, Government of South Australia: Adelaide)

Hamblin A, Tennant D (1987) Root length density and water uptake in cereals and grain legumes: How

well are they correlated? Australian Journal of Agricultural Research 38, 513-527.

Hamblin AP, Hamblin J (1985) Root characteristics of some temperate legume species and varieties on

deep, free-draining entisols. Australian Journal of Agricultural Research 36, 63-72.

Hamza MA, Anderson WK (2005) Soil compaction in cropping systems: A review of the nature, causes

and possible solutions. Soil & Tillage Research 82, 121.

Hamza MA, Anderson WK (2008) Combinations of ripping depth and tine spacing for compacted sandy

and clayey soils. Soil & Tillage Research 99, 213-220.

Hardie MA, Cotching WE, Doyle RB, Lisson S (2012) Influence of climate, water content and leaching

on seasonal variations in potential water repellence. Hydrological Processes 26, 2041-2048.

Hollaway KL, Kookana RS, Noy DM, Smith JG, Wilhelm N (2005) Persistence and leaching of

sulfonylurea herbicides over a four year period in the highly alkaline soils of south-eastern

australia. .

Hollaway KL, Kookana RS, Noy DM, Smith JG, Wilhelm N (2006) Crop damage caused by residual

acetolactate synthase herbicides in the soils of south-eastern Australia. Australian Journal of

Experimental Agriculture 46, 1323-1331.

Holloway R, Dexter A (1991) Tillage and compaction effects on soil properties, root growth and yield of

wheat during drought in a semi-arid environment. Soil Technology 4, 233-253.

Holloway R, Graham R, McBeath T, Brace D (2010) The use of a zinc-efficient wheat cultivar as an

adaption to cacareous subsoil: a glasshouse study. Pant & Soil 336, 15-24.

Holloway RE, Bertrand I, Frischke AJ, Brace DM, McLaughlin MJ, Shepperd W (2001) Improving

fertiliser efficiency on calcareous and alkaline soils with fluid sources of P, N and Zn. Plant and

Soil 236, 209-219.

Incerti M, O'Leary G (1990) Rooting depth of wheat in the Victorian Mallee. Australian Journal of

Experimental Agriculture 30, 817-824.

Jeffrey P, Hughes B (1995) 'Land zones of Eyre Peninsula. Key soils and land degradation of the

agricultural region.' Primary Industries South Australia, Adelaide.

King P (1974) Copper deficiency symptoms in wheat. Journal of Agriculture South Australia 77, 96-99.


Leonard E (Ed.) (2011) 'Spread, delve, spade, invert: a best practice guide to the addition of clay to sandy

soils.' (Grains Research and Developemt Corporation: Canberra)

Lewis D, Clarke A, Hall W (1981) Factors affecting the retention of phosphorus applied as

superphosphate to the sandy soils in south-eastern South Australia. Soil Research 19, 167-174.

Llewellyn R, D'Emden F (2009) 'Adoption of no-till cropping practices in Australian grain growing

regions.' Grains Research and Development Corproation, Canberra.

Ma Q, Rengel Z, Rose T (2009) The effectiveness of deep placement of fertilisers is determined by crop

species and edaphic conditions in Mediterranean-type environments: a review. Soil Research 47,

19-32.

Masters B, Davenport D (2012) Addressing produciotn constraints through the modificaiton of sandy

soils. In 'Eyre Peninsula Farming Systems Summary 2011'. (Eds N Scholz and et al.) pp. 166-172.

(South Australian Research and Development Institute: Minnipa)

Materechera S, Alston A, Kirby J, Dexter A (1992) Influence of root diameter on the penetration of

seminal roots into a compacted subsoil. Plant & Soil 144, 297-303.

May R (2006) 'Clay spreading and delving on Eyre Peninsula.' Primary Industries and Resources South

Australia, Minnipa.

Mayfield A, Trengove S (2007) Site specific benefits of deep ripping. In 'Eyre Peninsula Farming

Systems 2007 Summary'. (Eds N Scholz and et al.) pp. 154-155. (South Australian Research and

Development Institute: Minnipa)

McBeath T, Wittwer N, Whitbread A, Davoren B, Llewellyn R, Jones B (2011) Variable N and P rate

responses in a decile 10 season. In ' Mallee Sustainable Farming 2010 Results Compendium' pp.

8pp. (Mallee Sustainable Farming Project)

McBeath T, McLaughlin M, Kirby M, Armstrong R (2012) Dry soil reduces fertilizer phosphorus and

zinc diffusion but not bioavailability. Soil Science Society of America Journal 76, 1301-1310.

McBeath T, Davoren B, Llewellyn R, Gupta V, Jones B, Whitbread A (2013a) Soil-specific strategies for

cereal-based rotations. In 'Research Compendium 2012' pp. 7. (Mallee Sustainable Farming

Project)

McBeath T, Davoren B, Llewellyn R, Jones B, Whitbread A, Mason S (2013b) Variable N and P rate

responses. In 'Research Compendium 2012' pp. 5. (Mallee Sustainable Farming Project)

McBeath T, Gupta V, Davoren B, Llewellyn R, Whitbread A (2013c) Break crop benefits across soil

types. In 'Mallee Sustainable Farming Research Compendium 2012' pp. 6 pp)

McGrath GS, Hinz C, Sivapalan M, Dressel J, Pütz T, Vereecken H (2010) Identifying a rainfall event

threshold triggering herbicide leaching by preferential flow. Water Resources Research 46,

W02513.

McKenzie N, Jacquier D, Isbell R, Brown K (Eds) (2004) 'Australian soils and landscapes: an illustrated

compendium.' (CSIRO Publishing: Collingwood)

McKissock I, Walker EL, Gilkes RJ, Carter DJ (2000) The influence of clay type on reduction of water

repellency by applied clays: a review of some West Australian work. Journal of Hydrology 231–

232, 323-332.

Moodie M (2010) Regional WUE focus paddocks. In 'Karoonda trial site walk 2010' pp. 6-8. (Mallee

Sustainable Farming: Buronga)

Moodie M (2012a) 'Produciton and environmental impacts of borad leaved break crops in the Mallee.'

Mallee Catchment Management Authority, Mildura.

Moodie M (2012b) 'Mallee dryland agricultural soil health monitoring program 2102.' Mallee catchment

Management Authority, Mildura.

Nable RO, Webb MJ (1993) Further evidence that zinc is required throughout the root zone for optimal

plant growth and development. Plant & Soil 150, 247-253.

Newell J (1961) 'Soils of the Mallee Research Station, Walpeup, Victoria. Technical Report No. 13.'

Department of Agriculture, Victoria.

Norton R (2013) 'GRDC More Profit from Crop Nutrition II Micronutrient survey and scoping study. A

report for the Grains research and development Corporation.' International Plant Nutrition

Institute.

Nuttall J, Armstrong R, Connor D (2003a) Evaluating physicochemical constraints of Calcarosols on

wheat yield in the Victorian southern Mallee. Australian Journal of Agricultural Research 54,

487-497.


Nuttall J, Armstrong R, Connor D, Matassa V (2003b) Interrelationships between edaphic factors

potentially limiting cereal growth on alkaline soils in north-western Victoria. Australian Journal

of Soil Research 41, 277-292.

O'Connell M, O'Leary G, Connor D (2003) Drainage and change in soil water storage below the root zone

under long fallow and continuous copping sequences in the Victorian Mallee. Austraian Journal

of Agricultural Research 54, 663-675.

O'Connell MG, O'Leary GJ, Incerti M (1995) Potential groundwater recharge from fallowing in north-

west Victoria, Australia. Agricultural Water Management 29, 37-52.

Passioura J (1991) Soil structure and plant growth. Australian Journal of Soil Research 29, 717-28.

Passioura JB (2002) Soil conditions and plant growth. Plant, Cell & Environment 25, 311-318.

Paterson C, Sheppard W (2008) Soil compaction trials 2006-2008. In 'Eyre Peninsula Farming Systems

2008 Summary'. (Eds N Scholz and et al.) pp. 159-162. (South Australian Research and

Development Institute: Minnipa)

Peck DM, Howie JH (2012) Development of an early season barrel medic (Medicago truncatula Gaertn.)

with tolerance to sulfonylurea herbicide residues. Crop and Pasture Science 63, 866-874.

Pell SD, Chivas AR, Williams IS (2001) The Mallee Dunefield: development and sand provenance.

Journal of Arid Environments 48, 149-170.

Porker K, Wheeler R (2013a) Sulphur and nitrogen needs in Mallee barley crops- 2012. In 'Research


Porker K, Wheeler R (2013b) Sulphur and nitrogen responses of Barley in Mallee 2013. In 'Research


Price P (2010) Combating Subsoil Constraints: R&D for the Australian grains industry. Soil Research 48,

i-iii.

Proffitt A, Bendotti S, Howell M, Eastham J (1993) The effect of sheep trampling and grazing on soil

physical properties and pasture growth for a red-brown earth. Australian Journal of Agricultural

Research 44, 317-331.

Rebbeck M, Lynch C, Hayman PT, Sadras VO (2007) Delving of sandy surfaced soils reduces frost

damage in wheat crops. Australian Journal of Agricultural Research 58, 105-112.

Rengasamy P (2013) Soil pH - South Australia. In. (Ed. soilquality.org.au) 2.

Reuter D (2001) 'Nutrient balance in regional farming systems and soil nutrient status.' Canberra.

Roget D, Gupta V (1999) Mallee Sustainable Farming Project - Outcomes from the first year of trials. In

'Mallee Soils Seminar'. (Ed. J Lemon) 11-13. (Mallee Agricultural Research and Advisory

Committee: Esperance)

Roget D, Sadras V, O'Leary G, Davoren B, Schaefer R, Wormald D, Wormald J (2006) Compaction in

mallee soils - Problems and solutions. In 'Mallee Sustainable Farming 2002 - 2005 Summary' pp.

86-89. (Mallee Sustainable Farming: Mildura)

Roper M, Gupta V (1995) Management-practices and soil biota. Soil Research 33, 321-339.

Roper M (2006) Potential for remediation of water repellent soils by inoculation with wax-degrading

bacteria in south-western Australia. Biologia 61, S358-S362.

Roper M, Ward P, Keulen A, Hill J (2013) Under no-tillage and stubble retention, soil water content and

crop growth are poorly related to soil water repellency. Soil & Tillage Research 126, 143-150.

Roper M, Davies S, Blackwell P, Bakker D, Jongepier R, Ward P (2014) Management solutions for water

repellent ("non-wetting) soils in Australian agriculture - a review. Soil & Tillage Research

submitted.

Roper MM (2005) Managing soils to enhance the potential for bioremediation of water repellency. Soil

Research 43, 803-810.

Rovira A, McDonald H (1986) Effetcs of the herbicide Chlorsulforun on Rhizoctonia bare patch and

Take-all of barley and wheat. Planr Disease September 1986, 879-883.

Rowan J, Downes B (1963) 'A study of the land, in north western Victoria.' (Soil Conservation Authority

Victoria)

Rowland J (2001) Atlas of key soil and landscape attributes; Agricultural Districts of South Australia. In.

(Primary Industries and Resources, South Australia: Adelaide)

Sadras V, Baldock J, Roget D, Rodriguez D (2003) Measuring and modelling yield and water budget

components of wheat crops in course-textured soils with chemical constriants. Field Crops

Research 84, 241-260.


Sadras VO, O'Leary GJ, Roget DK (2005) Crop responses to compacted soil: capture and efficiency in

the use of water and radiation. Field Crops Research 91, 131-148.

Sanderman J, Farquharson R, Baldock J (2010) 'Soil carbon sequestration potential: A review for

Australian agriclture.' CSIRO Land and Water.

Smith J, Leys J (2009) 'Identification of areas within Australia for reducing soil loss by wind erosion.'

Bureau of Rural Sciences, Canberra.

Steenhuis TS, Hunt AG, Parlange J, Ewing RP (2005) Assessment of the application of percolation theory

to a water repellent soil. Soil Research 43, 357-360.

Stork P (1995) Field leaching and degradation of soil applied herbicides in a gradationally textured

alkaline soil: chlorsulfuron and triasulfuron. Australian Journal of Agricultural Research 46,

1445-1458.

Tennant D, Hall D (2001) Improving water use of annual crops and pastures- limitations and

opportunities in Western Australia. Australian Journal of Agricultural Research 52, 171-182.

Unkovich MJ, Pate JS, Hamblin MJ (1994) The nitrogen economy of broadacre lupin in southwest

Australia. Australian Journal of Agricultural Research 45, 149-164.

Walsh M (1995) Agricultural use of sandhill soils in the Victorian Mallee. La Trobe University.

Wheeler R, Davis L, Bennet M (2003) Response of cereal varieties to fluid fertiliser. In 'Eyre Peninsula

Farming Systems Summary 2003'. (Eds S Doudle and et al.) pp. 89-90. (South Australian

Research and Development Institute: Minnipa)

Whitbread A, Llewellyn D, B, Gupta V (2010) Farming to soil type in the Mallee to imrove water use

efficiency and reduce risk. In 'Mallee Sustainable Farming 2009 Research Compendium' pp. 52-

57. (Mallee Sustinable Farming)

Wilhelm N (2005) Deep placement of nutrients - few excuses left not to recommend it. In 'Eyre Peninsula

Farming Systems 2005 Summary'. (South Australian Research and Development Institute:

Minnipa)

Wong MTF, Bell RW, Frost K (2005) Mapping boron deficiency risk in soils of south-west Western

Australia using a weight of evidence model. Soil Research 43, 811-818.

Ying GG, Williams B (2000) Laboratory study on leachability of five herbicides in South Australian

soils. Journal of Environmental Science and Health, Part B 35, 121-141.


8 Appendix 1 – Workshop summary

A one day workshop was held at The Waite Campus Adelaide on 26 June 2014. The purpose of the

workshop was to discuss the findings of the draft report on constraints to crop production on coarse

textures soils of low rainfall south-eastern Australia. The 24 workshop participants included growers,

agronomic consultants and scientists from a range of agencies. Dr Phil Ward from CSIRO Floreat brought

us up to date on research in solution of problems on sandy soils in Western Australia where there has

been increased efforts in recent years.

Table 18 List of attendees at the workshop on potential constraints to crop production on sandy soils

in low rainfall south-eastern Australia and priorities for research.

Attendee Role

Ted Hancock Farmer (Murray Mallee, SA)

Neil Fettell GRDC Southern Panel, farmer (Central West, NSW)

Ed Hunt Consultant agronomist, farmer (Eyre Peninsula, SA)

Lou Flohr Consultant agronomist, farmer (Murray Mallee, SA)

James Hall Consultant soil scientist (SA)

Jeff Braun Consultant agronomist (Mid-north and Murray Mallee, SA)

Andy Bates Consultant agronomist (Eyre Peninsula, SA)

Ben Jones Consultant agronomist/scientist (Vic Mallee)

Murray Unkovich Consultant scientist

Simon Craig BCG research leader, farmer (Vic. Mallee)

Annie McNeil Soil scientist (University of Adelaide)

Nigel Wilhelm GRDC LRZ RCSN coordinator, SARDI ( SA)

Tim Herrmann Soil scientist (DEWNR, SA)

Naomi Scholz Project manager, SARDI (Eyre Peninsula, SA)

Melissa Cann Soil scientist (DEPI, Swan Hill, Victoria)

Amanda Schapel Soil scientist, (Rural Solutions SA)

Rebecca Tonkin Consultant agronomist (Rural Solutions, Lenswood SA)

Therese McBeath Soil scientist, CSIRO (Adelaide)

Gupta Vadakattu Soil biologist, CSIRO (Adelaide)

Rick Llewellyn Farming systems scientist, CSIRO (Adelaide)

Phil Ward Soil water scientist, CSIRO (Perth)

Nigel McGuckian Consultant ( facilitator)

Michael Moodie Consultant agronomist (SE Mallee)

Gemma Walker Executive manager, Mallee Sustainable Farming Inc., farmer (Vic)


Generally the workshop commended the scoping paper and endorsed the primary elements. The

presentations and discussions were very useful in better defining some issues and also raised some

additional issues.


Table 19 Comments on original scoping paper primary recommendations as follows

Scoping paper recommendation Workshop comment

ensuring that crops grown have deep rooting

capacity and deep rooting opportunity

endorsed as a priority

nutrients are accessible within the crop rooting

zone

possible problems of nutritional “desert” layers

prohibiting root growth should be considered

crop rotations include more regular broad leaf

species

lack of suitable crop choices remains a dilemma

movement of water and nutrients down the soil

profile are understood to the extent that they

can be predicted

ability to predict N mineralisation would also be

very useful

the extent of non-wetting and soil compaction

across the region are better defined

can we link actual defined soil type to likely

problems?

the specific causes of any soil compaction are

identified

extent and impact of natural physically

impenetrable layers in sands needs to be

investigated because some of these do not appear

to be traffic induced.

can we mitigate the effects of naturally

impenetrable layers?

soil organic matter is increased external input opportunities discussed

in assessing the efficiency of these systems and

any treatments, the focus should be on dry

matter production rather than yield in the first

instance as this provides greater insight than

grain yield analysis

analysis must also include an assessment of grain

yield and harvest index

Issues raised in addition to those in the original scoping paper

Additional issue Workshop comment

Frost problems of light coloured sandy soils less frost observed with claying. Relative

importance of albedo versus soil water storage

need to be ascertained if advice to be given

How do you decide whether to mitigate

problems or ameliorate soil with clay and/or

organic matter?

need some decision system/tipping points to

assist in decision making

How do you decide when to take soils out of

production?

need some decision system/tipping points to

assist in decision making


Attendees were asked to contribute questions that they had in relation to productivity of crops on sandy

soils, either in their region or more broadly. These questions have been grouped under relevant headings

and classified as either Research questions or primarily Extension questions

Table 20 Research questions raised by workshop participants in relation to mitigation of problems of

crop production on sandy soils

Theme Questions

Sandy Soils A series of questions around crop establishment technology, these are placed

under the “Water repellency” heading below

Need better understanding of sandy soil types and properties in NSW

Water Why don’t crop roots extract water from the subsoil?

Does water repellency reduce yield through effects on the seasonal water

balance as well as through poor crop establishment?

Is there lateral seepage of water from sandy rises and is it causing problems on

nearby mid slopes or break of slopes (e.g. bogging)?

Is bulk density and/or high soil strength implicated in poor root growth and

what is the relative contribution of traffic and compaction to poor root

penetration?

Nutrition How can we estimate nitrogen leaching and N mineralisation on sandy soils?

How do we get roots to grow into bleached, nutrient (e.g. Zn) deficient soil

layers ?

In non-calcareous sands P is generally available, but can it leach with N, can it

also tie up Zn?

What are the key nutritional constraints?

Does ability to grow through bleached layers differ between plant types?

Water repellency What is the impact of and options for dry sowing?

How do we define the extent and level of of non-wetting sands and do we

manage differently depending on “level” of non-wetting?

What seeding systems would improve germination (e.g. winged seeders)?

Erosion Legacy of erosion - what are our soils after movement of soils on to or down

from hills?

Main erosion risk is from having to resort to tillage for weed control for

difficult to control weeds

Rotational What legume should we grow to provide N, and how do we establish them?

opportunities How long will rotational benefits be available?


Need an N fixing crop with sufficient cover after harvest

Pests and Diseases Are there sub-clinical effects of pests and diseases effecting growth e.g.

Rhizoctonia?

Are crops on sands “weaker” and more susceptible to diseases/pests than on

other soils?

Do sands get colder than other soils and slow crop development?

Weeds/herbicides Is high chemical use on sandy soils (especially over summer) resulting in sub-

clinical phytotoxicity of crops, especially broadleaf crops?

Is lack of crop vigour a consequence of herbicide residues? (esp. for broadleaf

crops)?

Are herbicides moving on water repellent soils and damaging sown crops?

Table 21 Extension questions raised by workshop participants in relation to mitigation of problems of

crop production on sandy soils

Theme Questions

Sandy Soils Can we get better definition around soil types and their properties that give

predictive capacity for likely sandy soil problems?

Frost seems much worse on pale coloured sandy soils, is it reduced by claying?

Nutrition How well do K soil test interpretations relate to K uptake on sands?

Water repellency How do I establish pasture legumes and break crops?

How can I improve seed bed moisture for germination?

What is the appropriate measure of water repellency/non-wetting that we

should use?

What seeding systems would improve germination (e.g. winged seeders)?

How can the experience gained from seeding systems development in Western

Australia (no till, in furrow, in row, wetter application) best be transferred to

the Se Australian Mallee?


Table 22 Questions raised by workshop participants in relation to amelioration of sandy soils with clay

and/or organic matter amendments

Theme Questions

Soil amelioration Felt that mitigation strategies were required first, along with an assessment

of when one might opt for amelioration strategies

How can we replicate the “pipeline” effect (i.e. considerable and sustained

responses to major soil disturbances).

Can we better match the management or amelioration to those specific soil

definitions

How can we dissociate the critical factors with soil amelioration? (inversion,

delving, ripping)

What is the effect of amelioration of compaction in wetter years? (EP

research done in dry years)

What is the effect on compaction of ripping with deep placement of organic

amendment?

What is the impact on frost risk? Does it remove the frost risk?

What is the current guidance available to farmers waiting to renovate sandy

soils?

Can delvers be re-engineered to be more efficient and delve deeper? (half

the horse power and another 20 to 30 cm). Clay spreading helps with frost -

delving is better again. The areas where clay is shallow enough to delve can

be mapped (J Hall).

What is the problem that we are actually trying to solve? We are trying to

increase the surface area of the soil.

The potential role of mouldboard ploughing is yet to be considered. At this stage it is considered part of

the “amelioration” strategy which has not been advanced in the present analysis. Lessons from Western

Australia in this respect will be valuable. A summary of the exposé of Western Australian experience per

Phil Ward (CSIRO) as follows.


Phil Ward (CSIRO Floreat, recent progress with sandy soil research in Western Australia)

Sandy soils are responsive to management with respect to crop yield increases

Perception that water repellency is becoming worse in Western Australia.

Water repellency is a problem for dry seeding because tillage of dry soil exacerbates repellency, thus the

recent move toward dry sowing makes water repellency a more urgent problem

Mitigation It has been found that the combination of wetting agent and furrow sowing can

increase water use efficiency. No-till/residue retention also leads to higher soil water content despite

increased water repellency. Inter-row sowing provides two pathways for water infiltration and on-row

seeding is providing good water infiltration.

Amelioration Clay spreading is not very wide spread yet in WA. Mouldboard ploughing (ca 35 cm) is

increasingly popular. This buries water repellent layer yield responses of approximately 0.5 t/ha have

been sustained for 5 years so far but there is a significant risk of erosion which is yet to be realised.

Mouldboard ploughing brings with it the advantage of burial of weed seeds below a depth from which

they can emerge and it is likely that tis has been a big benefit.

Nutrition

• N - prone to leaching so split application best

• P - generally okay

• K, S and micro-nutrients - can often be deficient, so soil tests required

• Tissue testing - what is the plant drawing from the soil?

• Where in the soil profile are the nutrients?

Carbon

• Generally low in sandy soils

• No-till/residue retention increases soil carbon (relatively) but also increases water

repellency and water holding capacity and nutrient retention

• Role of perennial pastures still unclear

Knowledge Gaps

• why don’t roots grow into subsoil?

• Herbicide efficacy and movement (ridges and furrows)

• Nutrient availability with subsoil amelioration - need the roots to be active

• Rotation alternatives

• Diverse option farming systems are working better so there is a need for non-cereal

options to be developed


END OF P WARD SUMMARY

There were three presentations from growers/consultants highlighting what they thought were the primary

issues in their regions, a précis of their main points are as follows

Neil Fettell - sandy soils in south-central NSW (Griffith to south of Cobar)

Sandy soils - 20% of the landscape

Symptoms - poor growth and yield on sandy rises; prominently neutral pH to acid layers at depth;

establishment okay - poor tillering and some leaf tipping; residual soil water after harvest

Growers have tried a number of interventions

Ripping - short term response (may last a year), resettles quickly, difficulty in establishing crops -

fluffy soil

Deep lime incorporation - limited response

Nitrogen - move fertiliser away from seed row and apply N post emergent

Increase seeding rate (using mapping capacity for variable rates on sandy rises)

Reduce residual herbicide rates (can cut back on sandy rises)

Chicken litter - 2.5 and 5 t/ha, short term response, high rates not economic (farmers are doing

this on their own)

Jeff Braun (Murray Mallee and northern Yorke Peninsula, SA)

Frost and non-wetting a significant issue on white sands in the southern Murray Mallee

Concern about metrubuzen movement/damage to crops

Suggested that boggy patches were appearing between swales due to local water discharge

downslope and becoming a problem for tractability

Andy Bates (Eyre Peninsula)

Soils constraining crop growth, stratification of nutrients needs to be examined

Nutrients are declining in soil tests in the region (e.g. sulphur)

Establishment problems being tackled successfully but growth still not good even when

established

deep ripping effects short term


Inherent Sand Potential

Reduced Sand Potential

Raised Soil Potential

Poor root growthWater repellencyLow fertilityDeclining soil CRotational crops

AM

ELIO

RA

TIO

N

MIT

IGA

TIO

NA

MEL

IOR

ATI

ON

ClayingDelvingDeep rippingSoil reformingDeep nutrients

$

$

Establishment NutritionWeeds DiseaseRotations

Ongoing management

Workshop outcomes

The key workshop outcomes were as follows

Our definition of “sandy soils” was refined to “those soils where the primary constraints to crop

production are in the coarse textured part of the profile, not in a finer textured, or texture

contrast subsoil layers”. Thus the soils of interest are primarily deeper sands with the majority of

the seasonal plant available water and annual crop root growth in the sandy layer.

The workshop differentiated between (a) management opportunities which would address reduced

potential of sandy soils due to past and current management practices which might have resulted in

declining yields or declining yield potential of sandy soils used for cropping, and (b) potential

management practices which might radically alter the properties of sandy soils and result in a higher yield

potential than the soils in their “native state”. This distinction and the associated constraints to production

and potential management responses are illustrated in Figure 25, along with management issues which

would cut across all three situations. There was not opportunity to ask the attendees at the workshop to

rank the issues of Table 19 in terms of reaearch priorities, however, the mitigation options (Figure 25)

represent the relatively “low hanging fruit” in terms of research and development and should provide

substantial returns on investment by bringing crop yields to closer to the water limited potential of these

soils. To achieve this will require a combination of basic, stratgeic and applied research, and adaptation

and extension of existing technology from elsewhere in Australia.

Figure 25 Opportunities for mitigating current constraints and bringing crop yields closer to water

limited yield potentials on sandy soils, and for soil reformation through more radical amelioration

strategies.


The amelioration strategies represent somewhat of a revolution for agriculture in the region, but the

efficacy and economics of these new systems are yet to be rigorously evaluated. A new initiative by the

South Australian government, “NEW HORIZONS: A Clean Green Food Revolution For South

Australia”, will focus on applied research and engineering development and provides a potential portal for

developing an understanding of the primary drivers of yield responses in such ameliorated soils through

targeted parallel investment at sites established in the New Horizons program.


Page intentionally left blank


9 Appendix 2 - Example soil descriptions

Following are soil descriptions for some relevant sandy soils from South Australia. These provide a

formal description of some of the types of soils under consideration, selected merely on the basis that they

were readily available from Hall et al. (2009) at the time of writing. Relevant soils are not restricted to

those outlined below and it would be useful to source similar data for a range of target soils across low

rainfall SA Australia.


9.1 Murray Mallee

The Molineaux sand described here is equivalent to the Lowan Sand of Pell et al. (2001).


9.2 Eyre Peninsula

The origin of the sands on the Eyre Peninsula are not the same as those in the SE Australian Mallee.

A review of the potential constraints to crop production ... · compacted layer are from earlier...

Documents

Transcript of A review of the potential constraints to crop production ... · compacted layer are from earlier...