Response Of Winter Wheat Yield And Water And Nitrogen Use To Irrigation And Nitrogen Application In The Guanzhong Plain

Guanzhong Plain is an important grain production base in China.Fertilization and irrigation are the key factors to improve grain yield.Precipitation is scarce during the growing season of winter wheat,and the area of farmland holding irrigation is limited,and some wheat fields cannot be irrigated effectively.Winter wheat has different nitrogen uptake and utilization under different farmland moisture conditions,and the unsuitable amount of nitrogen application has caused nitrogen loss and reduced water and nitrogen utilization.In this study,a three-factor cracked zone field trial of winter wheat with N application,irrigation and variety was conducted at Cao Xinzhuang experimental farm in Yangling,China,from 2019-2021,with five N application gradients:no N application（N0）,75kg·hm^-2（N75）,150 kg·hm^-2（N150）,225 kg·hm^-2（N225）and 300 kg·hm^-2（N300）and three irrigation gradients:I2(1200 m³·hm^-2),I1(600 m³·hm^-2)and I0(0 m³·hm^-2),and the test materials were Xi Nong 979 and Pu Bing 151.Study on the effects of different on-farm moisture conditions and nitrogen application on yield and water and nitrogen utilization of winter wheat.In order to verify the long-term evolution trend and stability of winter wheat yield and water and N use under different irrigation and nitrogrn application treatments,we analyzed the evolution dynamics and stability of winter wheat yield and water and N use under different water and nitrogen treatments based on the quantitative simulation experimental results of DSSAT model under the same irrigation and nitrogen application treatments from 2008 to 2021,and to provide scientific theoretical basis for nitrogen application of winter wheat in dryland and irrigated agriculture,and promoting sustainable and efficient development of agriculture in Guanzhong Plain.The main results of study were shown as follow:1.Nitrogen application rate and irrigation rate significantly affected the nitrogen content of winter wheat plants and grains.When nitrogen application rate was 225 kg·hm^-2,the nitrogen content of stem did not increase significantly.On the basis of nitrogen application rates of 150 kg·hm^-2 and 225 kg·hm^-2 in dryland and irrigated farmland,grain nitrogen content did not increase significantly.The grain nitrogen content of I2 was significantly lower than that of I1 and I0.Nitrogen application and irrigation could maintain high aboveground biomass of winter wheat.Compared with the two varieties,Pu Bing 151had more advantages in dry matter accumulation than Xi Nong 979.2.Irrigation and nitrogen application rate and their interactions have significant effects on winter wheat yield,and the effects of irrigation rate and nitrogen application rate on yield components are different in different years.The yield of winter wheat did not increase significantly with the increase of N application rate or irrigation amount on the basis of N application rate of 150（225）kg·hm^-2 and irrigation amount of 600 m³·hm^-2.When the planting variety was Xi Nong 979,the nitrogen application rate increased by 28.4-110.1%compared with that without nitrogen application,and the irrigation rate increased by6.4-18.5%compared with that without irrigation.When the planting variety was Pu Bing151,the nitrogen application rate increased by 8.1-122%compared with that without nitrogen application,and the irrigation rate increased by 4.7-8.8%compared with that without irrigation.The production cost increased with the increase of nitrogen application rate and irrigation amount.Under the same irrigation treatment,the two varieties had higher net income and lower input cost when the nitrogen application rate was 150 kg·hm^-2.Compared with the two varieties,Pu Bing 151 was superior to Xi Nong 979.3.Soil water content from 0 to 200 cm decreased with the growth period of winter wheat,irrigation can effectively supplement soil water content.Water consumption increases under irrigation conditions.The nitrate-N content in soil could be increased by increasing n fertilizer application,but the leaching depth of nitrate-N was proportional to irrigation amount.Under the same irrigation treatment,the nitrogen application rate of 150 kg·hm^-2had higher nitrogen carrying capacity and lower nitrogen surplus,which could maintain the apparent balance of soil nitrogen.On the basis of this nitrogen application rate,the nitrogen surplus increased with the increase of nitrogen application rate.The NAE and NPFP decreased with the increase of N application rate.Nitrogen use efficiency can be improved by increasing irrigation water,and there were differences in water and nitrogen utilization between different years.In terms of irrigation,600 m³·hm^-2 irrigation during overwintering period can effectively supplement soil moisture,and on this basis,increasing irrigation will cause waste of water resources.Compared with the two varieties,Xi Nong 979 was more suitable for irrigated farmland and Pu Bing 151 was suitable for dry farmland,which was compatible with their characteristics.4.The establishment of model data set and the verification of model accuracy showed that DSSAT model could better simulate the yield and water use dynamics of winter wheat under different water and nitrogen treatments.Based on the historical meteorological data from 2008 to 2019,the response pattern of winter wheat yield and water use efficiency to nitrogen application or irrigation was simulated under winter wheat-summer maize rotation,The stability and sustainability of winter wheat yield and water and nitrogen use under different water status and nitrogen application rate were analyzed.Nitrogen application and irrigation can maintain the stability and sustainability of winter wheat yield and water and fertilizer use.Under the same irrigation（N application）,the variation coefficient of yield and water-fertilizer use efficiency decreased with the increase of N application rate（irrigation rate）,and the sustainability index increased with the increase of N application rate（irrigation rate）.The yield and WUE of N300 increased less than N225 under the same irrigation treatment.The grain yield and WUE of winter wheat were significantly increased with the increase of N application.WUE and NPFP decreased with the increase of irrigation amount and nitrogen application rate,respectively.There was no significant difference in nitrogen partial productivity among N150,N225 and N300 treatments in dry farmland.The Nitrogen partial productivity of irrigated farmland decreased with the increase of N application rate,and there was no significant difference between N225 and N300 treatments.Irrigation can improve nitrogen partial productivity of winter wheat,and there was no significant difference between I2 and I1 treatments.In summary,In the Guanzhong Plain,150 kg·hm^-2 of N applied to dry farmland can meet the N demand of winter wheat,considering that irrigated farmland will cause N leaching to the lower soil layer,suitable increase of nitrogen application rate on the basis of150 kg·hm^-2 irrigation farmland combined with 600 m³·hm^-2 irrigation in winter only,improve water use efficiency and nitrogen use efficiency,and obtain higher yield and economic benefits,but also maintain relatively stable soil fertility level and reduce nitrate leaching loss,which could be used as a reference index for nitrogen application rate and irrigation amount in agricultural production in Guanzhong Plain.