Influence of irrigation and nitrogen levels on Indian mustard

In a field study Indian mustard (Brassica juncea cv. Varuna) was grown under four levels of nitrogen (0, 30, 60 and 90 kg ha⁻¹) and three levels ofirrigation [60 mm water applied at irrigation water/cumulative open pan evaporation ratio (IW/CPE ratio) 0.7, 0.5 and 0.3]. Periodic observations on diverse growth parameters as well as on final dry matter and seed yield revealed that increasing nitrogen levels prgressively increased performance of the crop. The magnitude of improvement was more under the higher level of irrigation. The seed yield achieved with 60 kg N ha⁻¹ at the lowest level of irrigation (IW/CPE=0.3) was significantly higher than observed at the highest level of irrigation (0.7) without nitrogen fertilization. Increasing levels of N progressively increased the activities of various nitrogen and ammonia assimilating enzymes viz. nitrate reductase, glutamine synthetase, glutamate synthase and glutamate dehydrogenase. At 0.7 IW/CPE ratio the activities of all the enzymes increased upto 60 kg N ha⁻¹ and decreased at 90 kg N ha⁻¹ but the activities as such, remained higher than the control. However, at lower levels of irrigation (0.5 and 0.3) the increase in N levels, progressively increased the enzyme activities. Thus N fertilization had a favourable effect on both growth, yield and nitrogen metabolism at all levels of irrigation.