Fate of 15N Derived from Composts and Urea In Soils under Different Long-term N Management In Pot Experiments

Understanding of dynamics of N derived from organic N sources in soil is required for the development of sustainable agricultural systems. The aim of this paper is to compare, using pot experiments, the fate of N from urea (UF) and organic N sources such as rice straw compost (RC) and cattle compost (CC) using 15N labeled materials in paddy soil planted with rice. Two soils with a history of long-term applications of chemical fertilizers (LTCN) and organic N sources, i.e. straw compost +soybean cake, (LTON), were also compared. Nitrous oxide emissions were monitored during the growing period. Yield and N uptake of rice were higher in LTON soil than LTCN soil with no significant interaction with N applications. Chemical fertilizer increased yield and N uptake with a recovery rate by rice of 36 to 45%. Nitrogen recovery from RC and CC by rice was less than 10%. When recovery of N in soil was included with that recovered in the plant, 70% and 61% of applied N in the UF treatment was recovered from the LTCN a...