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Anne-Kristin Løes, Bioforsk Organic Food and Farming

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 College Ragnar Eltun, Bioforsk Arable Crops. Experimental field August 2002. Red clover and oats.

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Anne-Kristin Løes, Bioforsk Organic Food and Farming

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  1. 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 College Ragnar Eltun, Bioforsk Arable Crops Experimental field August 2002. Red clover and oats.

  2. Outline • Background and aim of the project • Experimental design • Results: Cereal yields, N balance, P and K dynamics • Conclusions • Consequences

  3. Background • Large and increasing demand for organic cereals (food and fodder) • Main challenges for organic cereal production: Soil structure Nutrient supply, especially N Weeds (perennial)

  4. Project aim • 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

  5. 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!

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

  7. 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

  8. Results I. N availability! Apelsvoll, June 2004.Photo Trond M. Henriksen. 1 2 6 5 0 2 5 6 1 0 2 5 0 6 1 6 0 5 2 1 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

  9. Results II. Cereal yields Tons ha-1 (15% water), average for both sites 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)

  10. Results III. Green manure biomass Kg N ha-1 in AGB of undersown ryegrass (2), clover (3) or clover+ryegrass (4) at Kise (K) and Apelsvoll (A)

  11. 50 0 Tr. 1 -50 Tr. 2 Tr. 3 -100 Tr. 4 Tr. 5 -150 Tr. 6 -200 -250 Results IV. Accumulated N balance 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.

  12. Results V. Nutrient deficiency? NPK concentrations at heading* *) Gorshkova, 1978. Proc. 8th Int Coll Plant Ana, Auckland New Zealand. Ferguson.. (ed). DSIR info service 134.

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

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

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

  16. Results VI. Increased P and K availability? 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)

  17. 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!)

  18. Conclusions • 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!

  19. Consequences and further studies • 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

  20. Thanks for your attention

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