Abstract:Aiming to investigate the effects of different combinations of irrigation and nitrogen on shoot biomass, yield, total nitrogen accumulation, and water and nitrogen use efficiency of drip fertigated spring maize in sandy soil area in Ningxia. The multivariate regression analysis method was used to obtain the best combination of irrigation and nitrogen for maximum production, and the spatial analysis method was further used to comprehensively evaluate the yield, grain nitrogen accumulation, and water and nitrogen use efficiency to seek a high-yield and low-water fertigation system for the closest acceptable production of multiple targets. The plot experiments were conducted with two factors of irrigation and nitrogen. There were three irrigation levels (W0.6: 0.6KcET0;W0.8: 0.8KcET0 and W1.0：1.0KcET0, Kc was crop coefficients, ET0 was potential reference crops evapotranspiration) and four nitrogen levels (N150: 150kg/hm2;N225: 225kg/hm2;N300: 300kg/hm2 and N375：375kg/hm2). The results showed that there was a high fitting degree of shoot biomass for spring maize with Logistic function and the W1.0 irrigation treatment delayed the starting point of the rapid accumulation period of shoot biomass. The single factor of irrigation and nitrogen application had significant or extremely significant effects on the yield, plant nitrogen accumulation and water use efficiency (WUE), and irrigation amount had significant effect on nitrogen partial factor productivity (PFPN). Both irrigation and nitrogen application amounts had significant or extremely significant effects on yield, plant nitrogen accumulation and WUE, while irrigation amount had extremely marked effects on PFPN, and irrigation and nitrogen had a notable coupling effect on the nitrogen harvest index. Under the same irrigation levels, the shoot biomass, yield, plant nitrogen accumulation (except for W0.8 treatment) and WUE were increased at first, and then decreased with the increase of the nitrogen application rate. Through the multivariate regression analysis and the spatial analysis methods, considering the uneven distribution of annual rainfall in Ningxia, the results suggested that when the sum of irrigation amount and effective rainfall was 506～576mm and nitrogen application rate was 230～335kg/hm2, the yield, WUE and grain nitrogen accumulation could reach more than 95% of the maximum yield, the PFPN under this combined treatment was about 80% of the maximum value at the same time. The research provided a guidance for scientific management of water and nitrogen application for spring maize under the local drip fertigated condition in sandy soil area in Ningxia.
