Mathematical model for the analysis of irrigation water and fertilizer management for spring wheat in the semiarid area of West Liaoning, China

Abstract

An experiment with a D-optimum saturation design (D-312) of three factors (N, P fertilizers and irrigation water) and five levels was used to assess the combined effects of N, P fertilization and irrigation water on the grain yield of spring wheat grown in the semiarid area of West Liaoning province, P. R. China. Best-fit predictive model of spring wheat grain yield was constructed by simultaneously including these three factors. The effects of N, P fertilizers and irrigation water on spring wheat grain yield were highly statistically significant. Although a previous study in the same area had shown that water was the most important factor affecting spring wheat grain yield, principal factor analysis in this experimental case indicated that, under normal rainfall conditions when the amount of irrigation water ranged from 45 to 360 mm, N fertilizer was the most effective factor, while marginal effect analysis demonstrated that the spring wheat grain yield response to N, P fertilizers and irrigation water met the law of diminishing returns. Increasing P fertilizer levels enabled to enhance the ability of spring wheat to tolerate drought during the period of water shortage. The most economic allocation of N, P, and irrigation water for 5,794 kg ha−1 spring wheat grain yield was 214.4 kg N ha−1, 37.5 kg P ha−1, and 349.6 mm of irrigation water. Optimum allocation of water and fertilizers not only increased the water use efficiency for spring wheat, but also enhanced the recovery of applied fertilizers.