Anne-Kristin Løes, Bioforsk Organic Food and Farming
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Transcript of Anne-Kristin Løes, Bioforsk Organic Food and Farming
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N supply in stockless organic cereal
production under northern temperate
conditions. Undersown legumes, or whole-
season green manure?
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.
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Outline
•Background
•Aim
•Experimental design
•Cereal yields
•N balance
•Conclusions
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Background•Large and increasing demand for organic cereals (food and fodder)
•Main challenges for organic cereal production:
Soil structure
(Perennial) Weeds
Nutrient supply, especially N
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• Is repeated undersowing of clover in cereals a well functioning green manuring strategy for commercial grain production on stockless organic farms?
Aim
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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
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Treatment2002Oats
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
No text = only cereals. Yellow = cereals. Clover = green. Undersown species = text.
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Records
•Yields of cereals and straw
•Aboveground biomass (AGB) - weeds - undersown crop(s) - cereals Recorded in early spring (endof April) – Mid Summer (earlyJuly) – harvest (early Sept.) -late autumn (late Oct.)
•NPK in AGB, % of dry matter (DM)
•Mineral N in soil (Nmin)Early spring and late autumn
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1
1
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1
0
0
0
0
2
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6
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6 5
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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.
Field at Apelsvoll, June 2004. Photo Trond M. Henriksen.
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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).
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Accumulated N balance
-250
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-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.
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• Considerable effect of green manuring, on average 30% larger yields the year after undersowing of clover
• Yield increase comes in the subsequent year
• One year out of four with clover ley gives a large yield increase, but not enough to compensate one year without cereal yields
• Combine whole-season green manure and undersown clover? Be aware of phytopathological risks! (nematodes, fungi, beetles)
• Without weed harrowing, undersowing increases the weed biomass. Combined harrowing and undersowing is desired.
• Negative accumulated N-balanse – cereal yields removed more N than the green manure produced
Conclusions
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•May low to medium concentrations of soil P and K decrease the potential of N fixation?
•Can we accept a larger 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
Modifications
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Thanks for your attention
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Kg N ha-1 in AGB of undersown ryegrass (2), clover (3) or clover+ryegrass (4) at Kise (K) and Apelsvoll (A)