Lysimeter studies on recovery of 15 N-labeled urea in wetland rice

摘要: Results of a two year study on the fate on15N-labelled urea (9.95 atoms percent excess15N) applied @ 180 kg N/ha to flooded rice in monolith lysimeters at Punjab Agricultural University Farm, Ludhiana are reported. The soil experimental field was sandy clay loam texture (Typic Ustochrept), had pH 7.9, organic carbon 0.36 percent, available N 187 kg/ha and total 0.08 percent. results revealed that 18.1 53.0 per cent fertilizer utilized by plant, 25.1 41.1 immobilized 4.8 7.2 lost denitrification. losses due ammonia volatilization leaching were negligible. data vertical distribution labelled profile reflected higher concentration (38.3 39.5 cent) surface (0–30 cm) soil. content sharply decreased (1.8 2.4, percent) lower layers (30–150 cm). A balance sheet various pathways showed 58.8 72.2 66.2 83.0 recovered 1976 1977, respectively 17 41.2 still remained unaccounted for. Utilization increased when three equal splits as compared single application transplanting. Availability investigated succeeding crops wheat rice. 2.1 tot 3.4 preceding second crop grown succession. This may look small but cannot be neglected long term basis. But there is need initiate studies investigate the, turnover residual determine varying cropping systems using improved techniques.