RESPONSE OF LATE-SOWN MUSTARD (BRASSICA-JUNCEA) TO IRRIGATION AND NITROGEN

The response of late-sown mustard (Brassica juncea L.) to four rates o f irrigation (ratio of irrigation depth to cumulative pan evaporation, ID:CPE = 0.2, 0.4, 0.6 and 0.8) and nitrogen (0, 30, 60 and 90 kg/ha) was investigated at Haryana Agricultural University, India, in the wi nter seasons of 1986/87 and 1987/88. Increases in the amounts of water and N fertilizer applied increased leaf water potential, stomatal con ductance, light absorption, leaf area index, seed yield and evapotrans piration and decreased canopy temperature. Water-use efficiency was hi ghest for the 0.4 ID:CPE irrigation treatment in both seasons, and for the 60 kg N/ha N treatment in 1986/87 and the 90 kg N/ha treatment in 1987/88. The combination of 0.6 ID:CPE with 60 kg N/ha gave a signifi cantly higher seed yield than lower rates and equalled that from the h ighest irrigation and N treatment combinations. The amount of water us ed by the mustard crop decreased with increasing soil depth irrespecti ve of treatment. In the deeper soil layers, the percentage of total mo isture use was greater under less irrigated than under more frequently irrigated plots. Leaf area index showed a significant positive linear relationship with evapotranspiration and light absorption and a negat ive linear relationship with canopy temperature. Seed yield was linear ly related to leaf area index and light absorption coefficient.