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 Weeds (perennial) Nutrient supply, especially N

4. 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

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. Treatments 2002 Oats 2003 Spring wheat 2004 Oats 2005 Spring wheat 2006 Spring barley 0 Control, weed harrowed 1 Control 2 Undersown ryegrass Ryegrass 3 Undersown clover Red cloverWhite clover Red cloverWhite clover 4 Undersown mixRed clover and ryegrass White clover and ryegrass Red clover and ryegrass White clover and ryegrass 5 Green manure mix Red clover and timothy Red clover and tim., ley 6 Green manure red clover Red cloverRed clover, ley 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 (N min ) Early spring and late autumn

8. 1 1 1 1 0 0 0 0 2 2 2 2 6 5 65 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.

9. Results II. Cereal yields Tons ha -1 (15% water), average for both sites Treat- ment Starting year, 2002Average 2003-05Residual effect, 2006 T / haRelative %T / haRelative %T / haRelative % 12.98 a1002.96 a1001.51 a100 22.83 a953.06 ab1031.71 a113 32.53 a853.86 b1291.99 a132 42.69 a903.76 ab1271.99 a132 52.68 a903.17 ab1071.73 a114 62.65 a893.23 ab1091.62 a107 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. 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

11. Results IV. Accumulated N balance Kg N / ha2002200320042005 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* % in DM Yield level, % of optimum yield Highly deficient, < 25-30% Low nutrient level, < 40-45% Oats, % of DM N<1.91.9-2.3 P<0.300.30-0.36 K<2.22.2-2.6 Spring wheat, % of DM N<2.22.2-2.5 P<0.210.21-0.23 K<1.71.7-2.0 *) 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! % of DM2002, oats2003, wheat2004, oats2005, wheat Apelsvoll 11,411,451,351,21 Apelsvoll 21,481,601,141,32 Apelsvoll 31,351,761,231,29 Apelsvoll 41,491,801,541,33 Gorshkova< 1,9< 2,2< 1,9< 2,2 Kise 11,461,100,841,13 Kise 21,451,100,851,21 Kise 31,331,271,391,34 Kise 41,411,131,611,37

14. Results V. Nutrient deficiency? Field experiment, P concentrations at heading. Deficient for oats, especially at Kise. OK for wheat. % of DM2002, oats2003, wheat2004, oats2005, wheat Apelsvoll 10,440,340,310,44 Apelsvoll 20,410,500,370,48 Apelsvoll 30,410,450,310,47 Apelsvoll 40,420,470,320,48 Gorshkova< 0,30< 0,21< 0,30< 0,21 Kise 10,290,340,150,25 Kise 20,260,290,150,26 Kise 30,230,360,210,25 Kise 40,290,310,260,25

15. Results V. Nutrient deficiency? Field experiment, K concentrations at heading. Deficient, except for oats at Kise 2002 % of DM2002, oats2003, wheat2004, oats2005, wheat Apelsvoll 11,781,280,771,48 Apelsvoll 21,741,541,101,56 Apelsvoll 31,821,341,131,52 Apelsvoll 41,811,511,131,55 Gorshkova< 2,2< 1,7< 2,2< 1,7 Kise 12,331,311,380,95 Kise 22,331,401,491,01 Kise 32,291,312,031,06 Kise 42,261,522,091,11

16. 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-NPKDMNPK ment- - - - - - - - - - Kg ha -1 - - - - - - - - - -- - - - Relative values - - - - A1102.427.887.47815100 A2113.937.2116.78765111134 112 A3137.738.5127.19739134139145125 A4157.641.0137.710177154148158130 K172.817.487.17174100 K267.114.687.06703928410093 K3124.625.7139.89430171148160131 K4116.423.6134.68520160135155119 Results VI. Increased P and K availability?

17. 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. 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

19. 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

20. Thanks for your attention