Grain yield response and N-fertiliser recovery of maize under deficit irrigation

Abstract

Grain yield response and nitrogen (N) fertiliser recovery of maize ( Zea mays L. cv. Sele) were assessed as influenced by deficit irrigation that was imposed either using conventional deficit irrigation (DI) or partial root drying (PRD) practice. The two deficit irrigation treatments were compared with FULL irrigation, the control treatment where rooting zone soil-water content was increased to field capacity at each irrigation, whereas 50% deficit irrigation was applied to the deficit treatments, DI50 and PRD50. Under the PRD practice, one-half of the rooting zone was wetted while the other half was maintained partially dry, thereby reduced amount of irrigation water was needed. The wetted and partially dry sides were interchanged in the subsequent irrigations. Under conventional DI, plants again received reduced amounts of water but the water was uniformly applied to both sides of the plant row. A popular hybrid maize–cultivar Sele was planted, following harvest of wheat. The study was conducted for two consecutive years in 2001 and 2002. A composite fertiliser of N, P and K, all at 80 kg ha −1 was applied before planting. At the ninth leaf (V9) stage, a second application of N-fertiliser at 170 kg N ha −1 rate was made. Difference method (plots with or without N-fertiliser application) was used for estimation of plant N-uptake efficiency. Contrary to earlier reports, the PRD treatment did not result in any yield benefit compared to the conventional deficit irrigation. The range of grain yield reduction under deficit irrigation treatments, DI50 and PRD50, was 10–25% and significant ( P ≤ 0.01), compared to FULL irrigation practice. Measurements, including xylem sap abscisic acid concentration, photosynthetic rate and stomatal conductance under DI50 and PRD50 treatments followed a nearly identical trend. The PRD irrigation practice had the highest N-fertiliser recovery among the irrigation treatments, with minimal mineral N residue left after maize harvest. The recoveries under FULL and DI50 treatments were 17 and 24% less, respectively, than the PRD treatment. The PRD irrigation practice was not only as effective as conventional deficit irrigation (DI) in saving water, but it should also be regarded as an environmentally friendly irrigation practice due to its association with low mineral N residue left in the soil.