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 significa...
