Abstract:
To explore the effects of different drip irrigation and fertilization levels on spring maize yield as well as water- fertilizer use efficiency, a 2-yr field experiment was carried out in the Water-saving Science and Technology District of Ningxia in 2016 to 2017. The spring maize variety of "Xianyu 335" was planted. There were 4 irrigation levels (75%ETc, 90%ETc, 105%ETc and 120%ETc, where ETc is the crop evapotranspiration) and 4 N-P2O5-K2O fertilization levels including 60-30-30 kg/hm2, 120-60-60 kg/hm2, 180-90-90 kg/hm2, 240-120-120 kg/hm2 in 2016, and 150-70-70 kg/hm2, 225-110-110 kg/hm2, 300-150-150 kg/hm2, 375-180-180 kg/hm2 in 2017. A control treatment with fully irrigated (120%ETc) with no fertilization was also set up. There were 17 treatments in total. The plant height, stem diameter, leaf area index (LAI), aboveground biomass and grain yield of spring maize were measured. The water use efficiency (WUE), irrigation water use efficiency (IWUE) and partial factor productivity of fertilizer (PFP) were also calculated. The 2-yr results showed that the single factor of irrigation and fertilization had significant or extremely significant effects on the plant height, stem diameter and LAI. Irrigation and fertilization had a significant coupling effect on the plant height of spring maize. The effects of irrigation and fertilization on the aboveground biomass at maturity varied with the fertilizer gradients. With low fertilizer application rate in 2016, the irrigation and fertilization treatments had significant effects on the aboveground biomass, with the maximum of 12 691 kg/hm2 in the treatment of irrigation 120%ETc and N-P2O5-K2O application rate of 180-90-90 kg/hm2. With the high fertilizer application rate in 2017, the aboveground biomass of 75%ETc and 105%ETc were first increased and then decreased with the increase in the irrigation amount and fertilizer application rate, reaching the maximum of 14 912 kg/hm2 in the treatment of 90%ETc and N-P2O5-K2O application rate of 300-150-150 kg/hm2. Irrigation and fertilization had a significant effect on the grain yield of spring maize in 2016, with the maximum of 14 400 kg/hm2 in the treatment of 120%ETc and N-P2O5-K2O application rate of 240-120-120 kg/hm2. The grain yield in 2017 reached the maximum of 16 884 kg/hm2 in the treatment of 90%ETc and N-P2O5-K2O application rate of 300-150-150 kg/hm2. In 2016, the WUE and IWUE were the highest in the treatment of 75%ETc and N-P2O5-K2O application rate of 180-90-90 kg/hm2 but the PFP was the highest in the treatment of 120%ETc and N-P2O5-K2O application rate of 60-90-90 kg/hm2. In 2017, the IWUE were the highest in the treatment of 75%ETc and N-P2O5-K2O application rate of 300-150-150 kg/hm2 but the PFP was the highest in the treatment of 90%ETc and N-P2O5-K2O application rate of 150-70-70 kg/hm2. By multiple regression, the treatments of irrigation and fertilizer application rate were different when the maximal yield, WUE and PFP were obtained. When the irrigation amount was 323-446 mm and the N-P2O5-K2O application rate was between 210-104-104 kg/hm2 and 325-163-163 kg/hm2, the yield and WUE could reach 95% confidence interval of maximal yield and maximal WUE while the PFP under the this combined treatment was only about 30% of maximal PFP. The results could provide guidance to field irrigation and fertilizer application in the field in Ningxia.