Carbon and Nitrogen Release from Legume Crop Residues for Three Subsequent Crops.

Lupwayi, N.Z. and Soon, Y.K. (2015). "Carbon and Nitrogen Release from Legume Crop Residues for Three Subsequent Crops.", Soil Science Society of America Journal, 79(6), pp. 1650-1659. doi : 10.2136/sssaj2015.05.0198  Access to full text


Pulse crops are grown on the Canadian prairies because of their agronomic, economic, and environmental benefits. They are recommended to be grown once every 4 yr, but N release from their residues is usually quantified over one crop season following their harvest. We estimated biologically fixed N and monitored patterns of C and N release from residues of green and forage pea (Pisum sativumL.), faba bean (Vicia faba L.), faba green manure (GM), and chickling vetch (Lathyrus sativus L.) GM in three subsequent crop years. Pulses fixed more N, particularly faba bean (184 kg N ha-1) and forage pea (165 kg N ha-1), than GM legumes (77 and 95 kg N ha-1), and they contained more C (1839–2577 kg C ha-1) than GM residues (1072 and 1240 kg C ha-1). Vetch GM, faba bean, and forage pea residues contained the most N (129–153 kg N ha-1), and green pea the least (65 kg N ha-1). Green manure residues released > 80% of their C and N contents, and pea residues released 46 and 62% of their C and about 50% of their N in the first year, but pea residues released more C and N than GM residues in the second and third years. Faba bean residues released 70% and 63% of their C and N, respectively, in the first year. After 3 yr, 3–5% of GM residue organic C and N remained in the soil, compared with 9–18% and 13–16% of pulse crop C and N, respectively. Therefore, pulse and GM residues had different patterns of C and N release.

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