Improving Water Productivity and Soil Fertility in Mustard (<i>Brassica juncea</i> L.) through Deficit Irrigation and Nitrogen Management in Semi-arid Region

A field experiment on deficit irrigation with nitrogen management in mustard was conducted at Anand, Gujarat, India during 2019-20 and 2020-21. Three main irrigation treatments based on IW/CPE (irrigation water/cumulative pan evaporation) ratio, namely, I1 (0.6 IW/CPE), I2 (0.8 IW/CPE), and I3 (1.0 IW/CPE) and five sub-treatments based on nitrogen levels, namely, N1 [100% recommended dose of nitrogen (RDN) through chemical fertilizer], N2 (100% RDN through vermicompost), N3 (75% RDN chemical fertilizer + 25% RDN vermicompost), N4 (50% RDN chemical fertilizer + 50% RDN vermicompost), and N5 (25% RDN chemical fertilizer + 50% RDN vermicompost + bio N-P-K consortium @ 1.0 L ha-1) were considered. The experiment followed a split-plot design with three replications. Pooled data analysis revealed that available soil phosphorus was significantly higher in treatment I3, while higher microbial counts were observed under treatment I2. Treatment N2 had a significant effect on soil available nitrogen (28 kg ha-1) and microbial count (130×107 cfu g-1). In treatment N2, soil quality parameters of pH and electrical conductivity (EC) showed a decrease, while organic carbon improved. On the other hand, available phosphorus and potassium improved in treatment N5. Interaction between irrigation levels and nitrogen treatments was found significant in case of soil available phosphorus. Also, a significant positive correlation was found between microbial count and available nitrogen content in the soil as revealed from the values of correlation coefficients for first year (71.32%), second year (76.9%) and pooled data (73.52%). Water productivity was found higher in treatments I1 (0.68 kg m-3) and N4 (0.68 kg m-3). This study concluded that optimization of irrigation schedule and adoption of balanced nitrogen management practices are essential for conserving resources, acclimatizing, enhancing soil health, and ensuring sustainable production in the long term.