Comparative assessment of critical stage and soil-moisture depletion irrigation scheduling for wheat using simulation modeling
DOI:
https://doi.org/10.48165/jefa.2026.21.1.31Keywords:
CROPWAT, irrigation scheduling, surface irrigation, wheat.Abstract
Surface irrigated wheat in semi-arid Indo-Gangetic conditions is commonly managed either by fixed-depth irrigations at critical phenological stages or by triggering irrigations when a fraction of total available water (TAW) is depleted. Using a calibrated CROPWAT framework for sandy loam soils and a 60 cm effective root zone, the present study compared (i) critical stage schedules with 40 mm fixed depths (2–6 events) against (ii) soil-moisture-depletion schedules at 50 per cent TAW refilled to field capacity. Seasonal water demand from the model was modest (ETc ≈ 224.7 mm). Under the stage based option, two irrigations at 22 and 85 DAS resulted in very high simulated yield reduction (~81.9%); three events (22, 65, 105 DAS) improved but still ~45.7 per cent loss, and adding a fourth or fifth event produced little further benefit. Only the six event schedule reduced losses to ~5.5 per cent. In contrast, the 50 per cent TAW triggered recommended three events centered on mid and late stages ( ≈ 101, 118, 131 DAS) with no simulated yield reduction, aligned applications with actual root zone deficits and avoided both early percolation and late stress. Results indicated depletion-based scheduling achieved yield protection with fewer, better-timed applications than fixed-depth stage calendars under surface irrigation.
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