Development and evaluation of drip irrigation and fertigation scheduling to improve water productivity and sustainable crop production using HYDRUS

Different nutrient application levels on okra's (Abelmoschus esculentus) growth and yield under drip fertigation was evaluated with a field experiment in comparison with flood irrigation. Results showed that drip fertigation improved the okra’s yield by 142% compared to surface flood (channel) irrigation and that this increase was statistically significant. An increase in nutrient applications above a recommended dose of fertilizers also significantly improved the yield by up to 100%. The HYDRUS model was calibrated and validated using the experimental data and various statistical parameters were used for comparing observed and predicted soil water content data. The volumetric soil water contents calculated using the HYDRUS model showed a good agreement with values measured at different horizontal and vertical distances from the drip emitter. The results also confirmed that soil water contents under drip irrigation were uniformly distributed within the root zone (i.e., 45 cm both vertically and horizontally from the plants). However, soil water contents were relatively low and showed larger variations within the plants' root zone under flood irrigation. Irrigation scheduling was simulated for the demonstration plots using the calibrated HYDRUS model for their respective soil conditions and validated with field observed soil water contents. An application of nutrients through drip fertigation improved crop yields in all demonstration plots, and an increase in yield over the control (flood irrigation) ranged from 13% to 317%. The benefit-cost ratio of drip fertigation for demonstration plots ranged from 2.05 to 3.50 for selected crops. Our study highlights that the adoption of drip fertigation with proper irrigation and nutrient scheduling (evaluated using HYDRUS) increases crop productivity and ensures higher efficiency of water, nutrients, soil fertility, environment sustainability, and profitable farming in Kerala.