Repeated undersowing of clover in organic

cereal production. Nutrient dynamics and

sustainability.

Anne-Kristin Løes, Bioforsk Organic Food and Farming

Trond M. Henriksen, Hedmark University CollegeRagnar Eltun, Bioforsk Arable Crops

Experimental field August 2002. Red clover and oats.

Outline

•Background and aim of the project

•Experimental design

•Results: Cereal yields, N balance,

P and K dynamics

•Conclusions

•Consequences

Background•Large and increasing demand for organic cereals (food and fodder)

•Main challenges for organic cereal production:

Soil structure

Weeds(perennial)

Nutrient supply, especially N

• Is repeated undersowing of clover in cereals a well functioning green manuring strategy for commercial grain production on stockless organic farms?

• For comparison: One year out of four with a whole-season green manure

Project aim

Experimental design

•Two sites, Kise and Apelsvoll•6 treatments, 4 replicates, 2002-06•2006 = residual effect, barley•2002-05 = repeated undersowing vs one year of green manure (2003)

•Mixing of grass and clover seed

Apelsvoll June 2004.Observe residual effects!

Treatments2002Oats

2003Spring wheat

2004Oats

2005Spring wheat

2006Spring barley

0 Control, weed harrowed

1 Control

2 Undersown ryegrass

Ryegrass Ryegrass Ryegrass Ryegrass

3 Undersown clover

Red clover

White clover

Red clover

White clover

4 Undersown mix

Red cloverand

ryegrass

White clover and ryegrass

Red clover and

ryegrass

White clover and ryegrass

5 Green manure mix

Red cloverand

timothy

Red clover

and tim., ley

6 Green manure red clover

Red clover

Red clover, ley

Yellow = cereals. Green = clover. Undersown species shown by text.

Experimental design, records

•Yields of cereals and straw

•Aboveground biomass (AGB) - weeds - undersown crop(s) - cereals Recorded in early spring, mid-

summer, at cereal harvest and in

late autumn

•NPK in AGB, % of dry matter (DM)

•Mineral N in soil (Nmin)Early spring and late autumn

1

1

1

1

0

0

0

0

2

2

2

2

6

5

6 5

6

5

5 6

Treatment 0: Weed harrowed, not included in main experiment. Treatment 1: No undersowing, tr. 2 ryegrass undersown. Treatment 5, 6: Red clover ley 2003, established 2002. Treatment 3, 4 (no numbers): Repeated undersowing of clover

Results I. N availability! Apelsvoll, June 2004. Photo Trond M.

Henriksen.

Results II. Cereal yields

Tons ha-1 (15% water), average for both sites

Treat-ment

Starting year, 2002 Average 2003-05 Residual effect, 2006

T / ha Relative %

T / ha Relative % T / ha Relative %

1 2.98 a 100 2.96 a 100 1.51 a 100

2 2.83 a 95 3.06 ab 103 1.71 a 113

3 2.53 a 85 3.86 b 129 1.99 a 132

4 2.69 a 90 3.76 ab 127 1.99 a 132

5 2.68 a 90 3.17 ab 107 1.73 a 114

6 2.65 a 89 3.23 ab 109 1.62 a 107

Within year or period, yields with different letters (a, b) are significantly different (p<0.05).

Average yield tr. 5+6 2004-05 = 4.80 t/ha vs 3.34 t/ha in tr. 1 (40% increase)

0

10

20

30

40

50

60

70

80

90

jul.0

2

okt.0

2

jan.

03

apr.0

3ju

l.03

okt.0

3

jan.

04

apr.0

4ju

l.04

okt.0

4

jan.

05

apr.0

5ju

l.05

okt.0

5

kg N

ha-1

2, K

3, K

4, K

0

10

20

30

40

50

60

70

80

90

jul.0

2

okt.0

2

jan.

03

apr.0

3ju

l.03

okt.0

3

jan.

04

apr.0

4ju

l.04

okt.0

4

jan.

05

apr.0

5ju

l.05

okt.0

5

kg N

ha-1

2, A

3, A

4, A

Kg N ha-1 in AGB of undersown ryegrass (2), clover (3) or clover+ryegrass (4) at Kise (K) and Apelsvoll (A)

Results III. Green manure biomass

Results IV. Accumulated N balance

-250

-200

-150

-100

-50

0

50

Tr. 1

Tr. 2

Tr. 3

Tr. 4

Tr. 5

Tr. 6

Kg N / ha 2002 2003 2004 2005

N balance = kg N in AGB of undersown green manure in late October x 1.25 minus kg N in cereals removed in September. Average for both sites.

Results V. Nutrient deficiency? NPK concentrations at heading*

% in DM

Yield level,% of optimum yield

Highly deficient,< 25-30%

Low nutrient level, < 40-45%

Oats, % of DM

N <1.9 1.9-2.3

P <0.30 0.30-0.36

K <2.2 2.2-2.6

Spring wheat, % of DM

N <2.2 2.2-2.5

P <0.21 0.21-0.23

K <1.7 1.7-2.0

*) Gorshkova, 1978. Proc. 8th Int Coll Plant Ana, Auckland New Zealand. Ferguson.. (ed). DSIR info service 134.

Results V. Nutrient deficiency? Field experiment, N concentrations at heading. Very deficient!

% of DM 2002, oats2003, wheat 2004, oats

2005, wheat

Apelsvoll 1 1,41 1,45 1,35 1,21

Apelsvoll 2 1,48 1,60 1,14 1,32

Apelsvoll 3 1,35 1,76 1,23 1,29

Apelsvoll 4 1,49 1,80 1,54 1,33

Gorshkova < 1,9 < 2,2 < 1,9 < 2,2

Kise 1 1,46 1,10 0,84 1,13

Kise 2 1,45 1,10 0,85 1,21

Kise 3 1,33 1,27 1,39 1,34

Kise 4 1,41 1,13 1,61 1,37

Results V. Nutrient deficiency? Field experiment, P concentrations at heading.Deficient for oats, especially at Kise. OK for wheat.

% of DM 2002, oats2003, wheat 2004, oats

2005, wheat

Apelsvoll 1 0,44 0,34 0,31 0,44

Apelsvoll 2 0,41 0,50 0,37 0,48

Apelsvoll 3 0,41 0,45 0,31 0,47

Apelsvoll 4 0,42 0,47 0,32 0,48

Gorshkova < 0,30 < 0,21 < 0,30 < 0,21

Kise 1 0,29 0,34 0,15 0,25

Kise 2 0,26 0,29 0,15 0,26

Kise 3 0,23 0,36 0,21 0,25

Kise 4 0,29 0,31 0,26 0,25

Results V. Nutrient deficiency? Field experiment, K concentrations at heading.Deficient, except for oats at Kise 2002

% of DM 2002, oats2003, wheat 2004, oats

2005, wheat

Apelsvoll 1 1,78 1,28 0,77 1,48

Apelsvoll 2 1,74 1,54 1,10 1,56

Apelsvoll 3 1,82 1,34 1,13 1,52

Apelsvoll 4 1,81 1,51 1,13 1,55

Gorshkova < 2,2 < 1,7 < 2,2 < 1,7

Kise 1 2,33 1,31 1,38 0,95

Kise 2 2,33 1,40 1,49 1,01

Kise 3 2,29 1,31 2,03 1,06

Kise 4 2,26 1,52 2,09 1,11

Accumulated uptake (2003-2005) of N, P and K in ABG dry matter at heading for treatments 1-4 at Apelsvoll (A) and Kise (K)Treat- N P K DM N P K DM

ment - - - - - - - - - - Kg ha-1 - - - - - - - - - -- - - - Relative values - - - -

A1 102.4 27.8 87.4 7815 100 100 100 100

A2 113.9 37.2 116.7 8765 111 134 134 112

A3 137.7 38.5 127.1 9739 134 139 145 125

A4 157.6 41.0 137.7 10177 154 148 158 130

K1 72.8 17.4 87.1 7174 100 100 100 100

K2 67.1 14.6 87.0 6703 92 84 100 93

K3 124.6 25.7 139.8 9430 171 148 160 131

K4 116.4 23.6 134.6 8520 160 135 155 119

Results VI. Increased P and K availability?

Results VI. Increased P and K availability?

• Uptake of P and K at heading reflects soil P and K concentrations (Kise 24 mg vs Apelsvoll 63 mg P-AL/kg soil, soil K medium level at both sites)

• Uptake of P and K reflects N availability (larger in treatments 3 and 4)

• At Apelsvoll (more fertile soil), undersown ryegrass also increased the accumulated P and K uptake (treatment 2)

• P and K uptake at heading more close to N uptake than to DM production

• This indicates increased bioavailability of P and K by undersown crops (not only N fixating!)

• Considerable yield effect of undersown clover. On average, + 30% the subsequent year. In the year of undersowing, slight yield decrease.

• Considerable yield effect of one year clover ley. On average +40% in two subsequent years. BUT this is not enough to compensate one year without cereal yields, as compared to repeated undersowing.

• The accumulated N-balance was negative in all treatments. Cereal yields removed more N than the green manure produced.

• Indications that undersown crops increase the bioavailability of P and K

• Possible to combine whole-season green manure and

undersown clover? Phytopathological risks!

Conclusions

•Cover crops, even those not fixing N, are useful in organic systems (ryegrass conserve N)

•What is the impact of soil P and K concentrations on the potential of N fixation? (rather low in this study)

•Can the farmers accept a large part of the crop rotation used for green manure (e.g. 2 years of clover ley, 3 years of cereals = 40%)?

•If no, what can be an acceptable source of N for organic stockless farms?

•Suggestions: Meat and bone meal, human urine

Consequences and further studies

Thanks for your attention