Carbon and Nitrogen Mineralization and Crop Uptake of Nitrogen from Six Green Manure Legumes Decomposing in Soil

Carbon and nitrogen mineralization from six green-manure legumes was studied in an incubation experiment. The values measured were fitted to a two-component and a one-component first-order model, respectively. Estimated parameters were compared. During 115 days of incubation approximately 30-35% of total N in white clover, black medic and subterranean clover was mineralized. Red clover and persian clover mineralized only 20% and egyptian clover 17%. White clover, black medic and subterranean clover showed a net mineralization during the whole incubation period. Red clover, persian clover and egyptian clover showed apparently an initial immobilization followed by a net mineralization after approximately 2 weeks. In a pot experiment, N uptake in rye grass from the six legumes was measured and comparisons were made with the incubation experiment after corrections for temperature differences. The amount of N harvested in the pot experiment was approximately 90% of the net N mineralization during decomposition.