Temporal Trends in Soil-Test P and Temporal Trends in Soil-Test P and P Recovery in Grassland SoilsP Recovery in Grassland Soils

Dr Michael HerlihyDr Michael Herlihy11 and and Dr Juliet Dr Juliet McCarthyMcCarthy1,21,2

11 Teagasc, Johnstown Castle Research Centre, Wexford Teagasc, Johnstown Castle Research Centre, Wexford22 Department of Life Sciences, University of Limerick, Department of Life Sciences, University of Limerick,

LimerickLimerick

The Irish Fertiliser Manufacturers’ Association

UNIVERSITY of LIMERICKO L L S C O I L L U I M N I G H

Outline of PresentationOutline of Presentation

BackgroundBackground IntroductionIntroduction Results:Results:

P balanceP balance Soil-test PSoil-test P P recoveryP recovery

Summary and ConclusionsSummary and Conclusions

BackgroundBackground

agronomic importanceagronomic importance environmental importanceenvironmental importance trends in fertiliser P use and trends in fertiliser P use and

soil Morgan P valuessoil Morgan P values

Fertiliser UseFertiliser Use

Courtesy of Soils Laboratory, Johnstown Castle

IntroductionIntroduction

Long-term trend: fertiliser P Long-term trend: fertiliser P vs.vs. soil-test P soil-test P Trends in Morgan P: build-up or depletionTrends in Morgan P: build-up or depletion Soil-test P changes in relation to P balanceSoil-test P changes in relation to P balance P balance = P inputs – P offtakesP balance = P inputs – P offtakes Potential for enrichment or depletion of Potential for enrichment or depletion of

soil-test Psoil-test P P recoveryP recovery

P balance trialP balance trial Component of larger trial: Component of larger trial: Fertiliser P Fertiliser P

requirements in relation to soil P status for grass requirements in relation to soil P status for grass production on representative soilsproduction on representative soils

Objective: examine trends in P balance, soil-test Objective: examine trends in P balance, soil-test PP

32 sites (8 x 4); low and high index groups; 4 yrs32 sites (8 x 4); low and high index groups; 4 yrs Fertiliser inputs: PFertiliser inputs: P00, P, P2020, P, P4040, once-off P, once-off P6060 kg ha kg ha-1 -1 P P Herbage and soil samplesHerbage and soil samples Paper: Paper: Irish Journal of Agricultural and Food Irish Journal of Agricultural and Food

ResearchResearch Focus: soils 14 and 30Focus: soils 14 and 30

Location of soil seriesLocation of soil series

Classification and characteristics of soil Classification and characteristics of soil seriesseries

Series / association†

Soil number

Parent material Drainage pH range

Association-13 13 Sandstone-limestone diamicton

Well drained 5.0 – 6.4

Clonroche 14 Ordovician shale diamicton

Well drained 5.8 – 6.5

Association-15 15 Sandstone-shale diamicton

Well drained 5.7 – 6.6

Castlecomer 22 Upper Carboniferous (Silesian) shale diamicton

Poorly drained 5.2 – 6.0

Baggotstown 30 Calcareous fluvio-glacial gravel

Well drained 5.6 – 6.9

Kinvara 33 Limestone diamicton (shallow)

Well drained 5.6 – 7.3

Elton 34 Limestone diamicton Well drained 4.8 – 6.5

Howardstown 39 Limestone diamicton Poorly drained 4.9 – 6.3

Results: P balanceResults: P balance

Effect of fertiliser P input on P balanceEffect of fertiliser P input on P balance

IndexIndex P inputP input SumSum††

1+21+2 00 -99.5-99.5

2020 -48.1-48.1

4040 12.512.5

6060 -59.7-59.7

3+43+4 00 -143.5-143.5

2020 -82.0-82.0

4040 -10.7-10.7

6060 -96.7-96.7

††Sum of 4 years (kg haSum of 4 years (kg ha-1-1))

Effects of soil series on P balance Effects of soil series on P balance

SumSum†† 1997 - 2000 1997 - 2000

SeriesSeries IndexIndex1 + 21 + 2

IndexIndex3 + 43 + 4

1313 -54.8-54.8 -109.4-109.4

1414 -48.9-48.9 -94.8-94.8

1515 -65.8-65.8 -102.6-102.6

2222 -7.6-7.6 -89.0-89.0

3030 -38.3-38.3 -55.6-55.6

3333 -79.9-79.9 -70.8-70.8

3434 -45.7-45.7 -85.5-85.5

3939 -- -58.1-58.1††Sum of 4 years (kg haSum of 4 years (kg ha-1-1))

Cumulative P balanceCumulative P balance†† for soils 14 and 30 for soils 14 and 30 IndexIndex Soil no.Soil no. P inputP input 19991999 20002000

1+21+2 1414 00 -87.7-87.7 -109.1-109.1

1414 2020 -38.4-38.4 -45.6-45.6

1414 4040 10.110.1 19.019.0

1414 6060 -36.8-36.8 -59.8-59.8

3030 00 -66.3-66.3 -79.5-79.5

3030 2020 -36.2-36.2 -41.0-41.0

3030 4040 7.47.4 17.717.7

   3030 6060 -34.4-34.4 -50.4-50.4

3+43+4 1414 00 -125.2-125.2 -159.7-159.7

1414 2020 -71.2-71.2 -87.3-87.3

1414 4040 -19.8-19.8 -20.3-20.3

1414 6060 -76.1-76.1 -112.0-112.0

3030 00 -90.2-90.2 -107.1-107.1

3030 2020 -54.6-54.6 -57.8-57.8

3030 4040 -3.2-3.2 9.59.5

   3030 6060 -49.9-49.9 -67.0-67.0††kg hakg ha-1-1

Results: Morgan PResults: Morgan P

Changes in P balance affect trends in soil-Changes in P balance affect trends in soil-test Ptest P

Effects of fertiliser P on Morgan PEffects of fertiliser P on Morgan P

(a) low index group

(Spring)

Effects of fertiliser P on Morgan PEffects of fertiliser P on Morgan P

(b) high index group

Trends in Morgan P: low index groupTrends in Morgan P: low index group

Soil 14mg l-1 P

Soil 30mg l-1 P

Trends in Morgan P: high index groupTrends in Morgan P: high index group

Soil 14

mg l-1 P

Soil 30

mg l-1 P

Results: Morgan PResults: Morgan P

Soil-test P decline esp. PSoil-test P decline esp. P00

Largest decline: higher indexLargest decline: higher index Change on PChange on P4040 plots plots nsns - annual - annual

fluctuations, inputs ~ offtakesfluctuations, inputs ~ offtakes PP2020 and P and P6060 Morgan P comparable Morgan P comparable

after 3 yearsafter 3 years Decline: 30 > 14Decline: 30 > 14

Unit change ratioUnit change ratio

Change P balance : unit change Change P balance : unit change Morgan PMorgan P

PP00 plots plots Low index: 79:1 (soil 14); 28:1 (soil Low index: 79:1 (soil 14); 28:1 (soil

30)30) High: 29:1 (soil 14) and 12:1 (soil 30)High: 29:1 (soil 14) and 12:1 (soil 30) Variation with index and P inputVariation with index and P input Effects of soil chemistry and textureEffects of soil chemistry and texture

% Recovery - P% Recovery - P6060

(a) low index group

%

(b) high index group

%

Results: P RecoveryResults: P Recovery

Highest on soil 30Highest on soil 30 Highest in low index groupHighest in low index group Increased with time … 4 yearsIncreased with time … 4 years May underestimate recoveries May underestimate recoveries

attainable over a longer periodattainable over a longer period

Summary of resultsSummary of results

Changes in P balance and soil-test P Changes in P balance and soil-test P affected by:affected by: Soil seriesSoil series Fertiliser P inputFertiliser P input Initial soil-P status (index)Initial soil-P status (index)

High offtakes reduced soil P rapidly: large High offtakes reduced soil P rapidly: large decline in 4 yrsdecline in 4 yrs

Depletion of soil P, fertiliser-P recovery Depletion of soil P, fertiliser-P recovery varied widely between contrasting soilsvaried widely between contrasting soils

Clonroche loam 14 Clonroche loam 14 vs.vs. light limestone light limestone Baggotstown 30Baggotstown 30

ConclusionsConclusions

Cannot assume direct relationships Cannot assume direct relationships between inputs and offtakes in different between inputs and offtakes in different soils soils

Effects of soil series, fertiliser-P inputs, P Effects of soil series, fertiliser-P inputs, P index on change in P balance, soil-test P index on change in P balance, soil-test P and recoveryand recovery

Large reductions in soil-test P in 4 yrs with Large reductions in soil-test P in 4 yrs with no fertiliser-P input … no fertiliser-P input …

Cut Cut vs.vs. grazed swards: offtakes, duration grazed swards: offtakes, duration Regular soil testing essentialRegular soil testing essential

Future WorkFuture Work

Differences in soil-test P Differences in soil-test P changes, recoveries between changes, recoveries between soils … causes?soils … causes?

AcknowledgementsAcknowledgements

IFMAIFMA Research Office, ULResearch Office, UL FarmersFarmers

The Irish Fertiliser Manufacturers’ Association

UNIVERSITY of LIMERICKO L L S C O I L L U I M N I G H