Optimizing wheat productivity and water productivity through deficit irrigation strategies in semi-arid environments

This study evaluated the effects of deficit irrigation strategies on wheat production, water productivity, and nitrogen dynamics in a semi-arid region of Pakistan. Field experiments were conducted over three crop seasons (2019-2022) with four irrigation treatments: 100% (I₁₀₀), 80% (I₈₀), 60% (I₆₀), and 40% (I₄₀) of crop evapotranspiration (ETc) requirements. Canopy cover dynamics exhibited quadratic relationships within days after sowing, attaining maximum covers of 95, 93, 89, and 75% under I₁₀₀, I₈₀, I₆₀, and I₄₀, respectively. Biomass accumulation followed similar quadratic trends, maximizing at 15.1 t ha^-1, 11.0 t ha^-1, 8.5 t ha^-1, and 6.0 t ha^-1 for the respective treatments. Irrigation significantly affected biomass yield (BY), grain yield (GY), and nitrogen uptake, with I₁₀₀ having higher values than deficit treatments. Relative to I₁₀₀, the BY decreases were 8% (I₈₀), 23% (I₆₀), and 48% (I₄₀), while the GY reductions were 7%, 23%, and 50%, respectively. Grain nitrogen uptake ranged from 123 kg N ha^-1 (I₁₀₀) to 59 kg N ha^-1 (I₄₀), mirroring yield trends. Water use efficiency based on biomass (WUE_b) and grain yield (WUE_g) remained consistent across I₁₀₀, I₈₀, and I₆₀ but dropped significantly under I₄₀. The yield response factor (K_y) analysis indicated that wheat exhibited moderate sensitivity to water stress, with K_y values of 1.25 (I₆₀) and 1.02 (I₈₀). These findings suggest that deficit irrigation at 80% ETc can optimize water conservation while sustaining wheat productivity and resource-use efficiency in semi-arid environments.