INFLUENCE OF NITROGEN ON INDIAN MUSTARD GROWN UNDER DIFFERENT LEVELS OF STORED SOIL-MOISTURE

Responses of Indian mustard to different levels of stored soil moistur e (100, 90, 75 and 60% of field capacity) and nitrogen doses (0, 30 an d 60 kg ha-1) were studied. Decreasing moisture levels caused a genera l decline in all observed parameters. Nitrogen fertilization enhanced the soil moisture extraction (especially below 40 cm depth) and increa sed the water use through larger leaf area, particularly during the ve getative period without affecting the water use during the reproductiv e phase. An increase in nitrogen dose increased dry matter production, seed yield, water use efficiency, nitrogen and phosphorus uptake coup led with increased levels of total chlorophyll, starch, reducing sugar s, soluble protein and free amino acids, despite a consistent decline in plant water potential and percentage relative turgidity at all leve ls of stored moisture. Notwithstanding the decline in the activities o f nitrate reductase and glutamine synthetase under low soil moisture, the increase in glutamate dehydrogenase activity on one hand and nitro gen mediated increases in all these enzymes irrespective of soil mosit ure status, on the other, possibly helped the fertilized plants to mai ntain ammonia assimilation.