Effects Of Irrigation Quota Under Nitrogen Reduction On The Growth,Yield And Water-Nitrogen Use Efficiency Of Spring Wheat In Ningxia Yellow River Diversion Irrigation Area

Aiming at the problems of excessive nitrogen fertilizer input and low water resource utilization efficiency in the production of spring wheat in Ningxia Yinhuang Irrigation District,the impact of water-saving irrigation on the growth,yield and water and nitrogen utilization efficiency of spring wheat under the background of nitrogen reduction is discussed,and it is of great significance to improve the efficiency of water and nitrogen use,reduce nitrogen fertilizer loss and water waste and reduce soil environmental pollution caused by excessive water and nitrogen on the basis of ensuring yield,which is of great significance to promote the development of efficient and green production mode of spring wheat in Ningxia Yinhuang Irrigation Area.In 2021,the experimental experiment of spring wheat nitrogen application and irrigation quota was carried out in the experimental farm of Ningxia University in Ningxia Hui Autonomous Region,and three nitrogen application levels were set:conventional nitrogen application NC(270 kg·hm-2),nitrogen reduction fertilizer 25%NJ(202.5 kg·hm-2)and non-nitrogen fertilizer NO(0 kg·hm-2),three irrigation quotas:conventional irrigation WC(400 mm),water saving 20%W1(320 mm)and water saving 40%W2(240 mm).Using Ningchun No.4 as the test material,the growth,yield and yield components of spring wheat under different water and nitrogen treatments,nitrogen uptake,soil water and nitrogen distribution and water and nitrogen use efficiency were studied.The main findings of the study are as follows:(1)Different irrigation treatments under the same nitrogen application level had no significant effect on the total number of stems in the group,but the water-saving treatment maintained a high total number of stems in the group;compared with conventional nitrogen application,the nitrogen reduction of 25%had no significant effect on the growth and development of spring wheat,under this premise,the water saving of 20%significantly increased the height of spring wheat plants,leaf area,etc.,increased the accumulation of dry matter in the upper part of the ground,and significantly increased the SPAD value of flag leaves,significantly improved the photosynthetic rate of spring wheat flag leaves,and promoted the growth of spring wheat Significantly improved the stem strength of spring wheat at the filling stage,which was increased by 18.09%and 26.48%compared with WC and W2 treatments,respectively.(2)The total nitrogen content of the plants decreased with the decrease of the irrigation quota at the same nitrogen fertilizer level,and the total nitrogen content of the WC and W1 treatments was significantly higher than that of W2,and the nitrogen accumulation of the NJW1 treatment was up to 272.12 kg·hm-2.The total nitrogen content in the grain and shell+panicle axis of the W1 treatment increased by 19.92%,25.38%,19.65%and 32.62%respectively compared with the WC and W1 treatments,respectively,and the distribution ratio of the W1 treatment in the grain was as high as 59.56%.(3)The soil moisture content of the water and nitrogen treatment changed significantly with the change of time,the soil volume moisture content in the late growth period was lower than that in the pre-growth period,and the general trend of the soil volume moisture content of the same soil layer under different irrigation treatments was WC>W1>W2,and the soil moisture transport change was mostly above the 60 cm soil layer.(4)The total soil nitrate nitrogen accumulation under the conventional nitrogen application and nitrogen reduction levels was reduced by 23.86%,38.60%,18.95%and 27.40%respectively compared with the WC treatment,and the total soil nitrate nitrogen accumulation in the NCWC treatment was the highest,reaching 218.55 kg·hm-2.Nitrogen surplus from large to small performance NC>NJ>N0,under the conventional nitrogen application and nitrogen reduction level with the reduction of irrigation quota performance is first reduced and then increased,under the nitrogen reduction level W1 treatment to improve crop nitrogen uptake,reduce soil nitrogen residue,in order to reduce nitrogen loss.(5)The number of panicle grains and the 1,000 grain weight of the W1 treatment were the highest at the nitrogen reduction level,reaching 42.87 grains and 54.28 g,respectively,which significantly increased the grain yield of spring wheat up to 8092.52 kg·hm-2,followed by the W1 treatment at the conventional nitrogen application level,which increased by 7.01%and 2.97%respectively compared with the conventional irrigation treatment of conventional nitrogen application,and significantly increased the protein and soluble sugar content of spring wheat grain.The agronomic efficiency,nitrogen fertility and nitrogen utilization efficiency of the W1 treatment were higher under conventional nitrogen application and nitrogen reduction levels,and the nitrogen reduction level was better than that of conventional nitrogen application.At the same time,the water use efficiency of the W1 treatment under the nitrogen reduction level was also higher,and the water use efficiency under the W1 treatment was 1.62 kg·m-3,which was 21.80%and 1.25%higher than that of the WC and W2 treatments.