Impact of 15N-labeled rice straw and rice straw compost application on N mineralization and N uptake by rice

Incorporation of plant residues in soil affects N and C content and dynamics. This study determined the effects of short-term alternative rice (Oryza saliva L.) residue management on N mineralization and uptake by rice. Pot and laboratory incubation experiments were established by incorporating N-15-labeled rice straw and rice straw compost in paddy soil. The N-15 recovered by rice averaged 16.6%; most of this recovered N-15-fertilizer was cycled through soil pools and only small amounts originated from labeled rice residues. At harvest, denitrification rate of rice straw and rice straw compost was 27.2% and 38.5%, respectively in the pot experiment, while residual N in soil ranged from 56.2% and 55.1%, respectively. The incubation study showed that about 22-26% of N from N-15-labeled rice straw was mineralized over a period of 105 days. Recovery of residual N-15 fertilizer appears to contribute little to total inorganic N. The results showed that rice residues exerted a small and short-term positive effect on N mineralization and N uptake.