Salinity-fertility interaction on growth, photosynthesis and nitrate reductase activity in sesame

Interactive effects of soil salinity (0, 3, 6 and 9 dSm⁻¹ approximately) and soil fertility (LF-N₀P₀ and IF-N₆₀P₄₀) were studied on net photosynthesis, leaf diffusive resistance, nitrate reductase activity, mineral composition and on growth and yield of sesame (Sesamum indicum L.) with a view to alleviate the adverse effects of salt stress through improvement of soil nutritional status. Although a progressive decline with increasing salinity was recorded in all the observed parameters but seed yield and dry matter production were significantly higher in plants raised at improved soil fertility (IF) as compared with low fertility (LF) plants at all levels of salinity. The magnitude of the detrimental effects of salt stress was also less in IF than LF plants. The improved nutritional status induced a higher photosynthetic efficiency coupled with higher chlorophyll concentration and more favourable concentrations of N, P and K as well as wider K:Na ratios in the fertilized plants despite salt stress. The activity of nitrate reductase was adversely affected by increased salinity but it was consistently higher in IF as compared to LF plants at all salinity levels. These changes possibly contributed to the better performance of improved fertility plants both under control as well as salinity stress conditions. The results indicate the importance of fertilizer application under salt stress for achieving sustainable yields.