Compensation Effects of Planting Density and Fertilization on Grain Yield, Water Use Efficiency and Seeds Nutrient Contents of Dry Land Spring Wheat

To assess the compensation effects of input fertilizers on the crop yield and water use efficiency (WUE), two-year experiments of spring wheat planting density and fertilization influence yield formation were conducted in the semiarid field conditions of loess hilly area in Ningxia Uh autonomous region. A comparison of wheat yield and WUE sequences under four planting densities with five fertilization levels shows that maximum yield and highest WUE were achieved under the optimum fertilizer input of 90 kg N and 135 ckg P2O5 per hm2 with 500 seeds/m^2. Increase soil fertilization was positively correlated with grain yield and water use efficiency of spring wheat, with a correlation coefficient were 0.959 and 0.894, planting density, however, showed poor correlation with both. Increasing fertilizer level significantly increased fertile spikelets number, kernels per spike and kernel weight. These components were decreased with the increase in planting density. Fertile spikelets number was sensitive to fertilization, whereas kernel number and weight was mainly affected by plant density. Fertilization applied in spring wheat improved root system development and especially enhanced roots growth in the cultivated soil layer of 0~20 cm. Ameliorated root system was able to improve crop water use and nutrient absorption, and hence, crop yield and water use efficiency was increased. Grain yield of spring wheat was increased by 44.6% and 55.4% when P and P+N +K were applied, respectively. A significant increase in yield was also obtained with N application but not with K. P or P+N promoted spike development and hence, increased seed production. N+P+K improved the quality of seeds, and the content of N, P and K in seed increased by 18.5%, 18.4% and 8.1%, respectively, compared with no nutrient treatment. This study highlights the compensation effects of improving soil fertility to high efficient use of limited water in dry land spring wheat production.