Effect of Some Organic Chemicals on Soil Organic Nitrogen Fractions and Their Availability in a Rice-Wheat Sequence

In a green house study, 2, 4-dinitrophenyl hydrazone and naphthyl ethylene diamine were found effective in providing higher mineral N during rice growth. Their application also increased the yield of both rice and wheat in the subsequent season. Characterization of soil organic N after rice showed that the hydrolyzable unidentified N (HU-N) increased with chemical application, where as the content of hydrolyzable NH₃-N (HA-N) and amino sugar N (AS-N) decreased irrespective of the treatments; and aminoacid N (AA-N) showed little change with the chemicals but decreased considerably in control. The content of HU-N and AA-N formed the major portion of total hydrolyzable N (TH-N) after rice. The AA-N and HA-N were found to be dominant fractions in TH-N, whereas AS-N contributed minimum towards TH-N initially and also after rice. The content of TH-N and HA-N (after rice) showed significant positive correlation with grain yield of wheat.