Salinity‐fertility interaction on growth, mineral composition and nitrogen metabolism of Indian mustard

Indian mustard (Brassica juncea L.) was grown under low fertility (LF) and improved fertility (IF) [60, 40, and 20 kg/ha N, P2O5, and K2O, respectively] and irrigation with saline waters of different concentrations (0, 50, 100, and 150 meq/L) of the same composition as local ground waters. Although a progressive decline with increasing salinity was observed on all observed parameters, growth and seed yield was consistently and significantly greater for the IF as compared to LF plants. The magnitude of the detrimental effects at increasing salinity was also less in the IF as compared to the LF plants. These results suggest that an improvement in the concentration and uptake of NPK, particularly N, and an increase in K:Na ratio under IF, stimulated nitrate reductase (NR) activity as well as the ammonia assimilating enzymes, such as GS, GOGAT, and GDH, despite the high salinity. This led to higher levels of free amino acids and soluble protein in the plants. Starch tissue content also showed a marked increase. This suggests the importance of fertiliser treatment under salt stress.