Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, 110012.
* Present address: Micronutrient Project (ICAR), Gujarat Agricultural University, Anand, Gujarat, 388 110.
The effectiveness of two organic chemicals, viz. 2, 4-dinitrophenyl hydrazone and naphthyl ethylene diamine applied @ 10 mg kg−1 soil to wheat were studied as mobilizers of recently immobilizedfertilizer N applied (15N urea) @ 60, 120 and 180 mg kg−1 soil to rice under greenhouse condition on a Typic Ustochrept. Rice as a first crop gave 15N recovery ranging from 35 to 37 per cent and more than one third of the applied fertilizer N was retained in the soil. Chemicals provided significantly higher mineral N during the initial growth period of wheat grown as a subsequent crop on the soil having different levels of residual nitrogen. 15N removal by plants at all the growth stages was significantly higher due to chemicals. The chemicals also showed significant effect in increasing the grain yield which caused higher N uptake and showed 15N recovery escalation. The 15N recovery at wheat harvest varied from 3 to 5 per cent of total 15N applied to the first crop of rice and left a negligible amount of 15N as unaccounted for with respect to the quantity retained in the soil at rice harvest.
Nitrogen utilization, 15N recovery, 15N balance, organic chemicals, residual fertilizer N, recently immobilized fertilizer N, rice-wheat sequence
