Soil Moisture Dynamics, Bulk Density, and Economic Water Productivity of Wheat as Influenced by Irrigation Scheduling and Hydrogel Application

Abstract

Aims: To evaluate the effects of irrigation scheduling and hydrogel application on soil moisture dynamics, soil bulk density, economics and economic water productivity of wheat. Study Design: A field experiment was conducted in a split-plot design with three replications; the irrigation schedule was the main-plot factor, and hydrogel treatment was the sub-plot factor. Place and Duration of Study: Bihar Agricultural University, Sabour, Bhagalpur, Bihar, India, during the winter (Rabi) season of 2020-21. Methodology: Three irrigation schedules (I1: one irrigation at CRI; I2: two irrigations at CRI and boot leaf stage; I3: three irrigations at CRI, late jointing and milking stage) were combined with four hydrogel treatments (Eco Sarovar, Vedic, Vaaridhar G1, Nano) and an untreated control. Soil moisture content was measured by time-domain reflectometry before and after each irrigation event; bulk density was measured before sowing and after harvest; and cultivation cost, gross and net returns, benefit:cost ratio, and economic water productivity (EWP) were computed from input costs and prevailing market prices. Results: Each irrigation produced a sharp rise in soil moisture followed by progressive depletion. Nano hydrogel sustained the highest soil moisture content at every stage, with moisture depleting 26-30% more slowly than in the control; under one irrigation, it retained more harvest-stage moisture (18.95%) than the control retained under two irrigations (13.24%). Nano hydrogel reduced post-harvest bulk density to 1.406 g cm-3 compared with 1.424 g cm-3 in the control, with a correlation of r = -0.93 between residual moisture and bulk density. Three irrigations gave the highest gross return (Rs 100,990 ha-1) and net return (Rs 58,082 ha-1); Nano hydrogel gave the highest gross and net returns among sub-plot treatments, but EWP declined with irrigation frequency (56.07 to 26.89 Rs m-3) and was highest under Vedic hydrogel among the cost-efficient treatments. Conclusion: Hydrogel amendment, particularly Nano hydrogel, improves soil moisture retention, soil structure and economic returns from wheat, while Vedic hydrogel offers the most favourable return per unit of investment.