| The shortage of water resources,the excessive nitrogen input and the environmental problems are the key to restricting the sustainable development of agriculture in North China.The effects of irrigation and nitrogen application on the yield,water and nitrogen use efficiency,nitrate nitrogen leaching of summer maize and winter wheat were studied to improve resource use efficiency and reduce environmental pollution risks while maintaining high yields.Meanwhile,realizing the optimization goal of high yield and efficiency and reducing environmental pollution,it provides technical reference for field water and fertilizer management of summer maize and winter wheat cultivation.This paper carried out field trials at the Beijing Irrigation Experimental Station from 2019 to 2020,four irrigation levels were set for the summer maize season（W0:0,W1:60 mm,W2:120 mm,W3:180mm）and four irrigation levels were set for the winter wheat season（W0:0 mm,W1:80 mm,W2:140mm,W3:200 mm）,four nitrogen application levels were set in both seasons(N0:0,N1:150 kg·hm-2,N2:275 kg·hm-2,N3:400 kg·hm-2).The effects of irrigation and nitrogen application on water consumption,growth,nitrate nitrogen accumulation,yield,water and nitrogen use efficiency of maize and wheat under precipitation conditions were studied,and use multiple regression analysis to comprehensively evaluate multiple indicators of maize and wheat.The results showed:（1）Reducing irrigation amount can reduce the ineffective water consumption,and nitrogen application increases the proportion of soil water storage consumption to field water consumption.At the W1 level of maize,the soil water consumption of the N1 treatment accounted for an increase of 16.99%compared with the N0 treatment.At the W2 level of wheat,the soil water consumption of N1 treatment accounted for 3.56%higher than that of N0 treatment.（2）Irrigation and nitrogen application can significantly increase the plant height,leaf area index,dry matter accumulation and nitrogen accumulation of maize and wheat,and reduce the root shoot ratio,but when the water and nitrogen application exceed a certain range,it will inhibit crop growth.When the maize treatment is W1N1 and the wheat treatment is W2N1,the growth indicators can maintain a high level.（3）The soil nitrate nitrogen accumulation was significantly positively correlated to nitrogen application rate,when the treatment is N1,the soil nitrate nitrogen content after wheat harvest is not only beneficial to the growth of the next crop,but also reduces the risk of leaching loss.Nitrate nitrogen was mainly distributed in the 0-60 cm soil layer in treatment W0,irrigation was contributed to migration of nitrate nitrogen to deeper soil and increased the risk of nitrate nitrogen leaching.（4）Nitrogen application has a critical effect on the yield of maize and wheat,both of maize and wheat reached the maximum in N1 treatment,which increased by 29.54%and 30.43%compared with N0treatment,respectively.Furthermore,excessive nitrogen application would inhibit the increase in yield.When the maize treatment was W1 and the wheat treatment was W2,the yield was significantly increased,which was 18.89%and 33.91%higher than that of the W0 treatment,respectively,and increasing irrigation will not increase production.（5）The relationship between nitrogen application and NPFP,NAE and NUE was negative,however,WUE and IWUE showed an increasing trend at first then while decreasing,and N1 nitrogen treatment can maintain a high water and nitrogen use efficiency.Under the level of N1 nitrogen application,higher water and nitrogen use efficiency appeared at W1 treatment in maize and W2 treatment in wheat,and excessive irrigation is not beneficial to nitrogen fertilizer rational utilization,and reduces WUE.（6）Using multiple regression analysis,yield,water and nitrogen use efficiency reached more than95%of their optimal values simultaneously when the irrigation amount was 81-102 mm and the nitrogen application was 143-161 kg·hm-2of summer maize.Yield,water and nitrogen use efficiency reached more than 90%of their optimal values simultaneously when the irrigation amount was 105-126 mm and the nitrogen application was 125-158 kg·hm-2of winter wheat,and the accumulation of nitrate nitrogen after harvest was low.In summary,maize irrigation is 81-102 mm and nitrogen application is 143-161 kg·hm-2 under dry precipitation conditions,wheat irrigation is 105-126 mm and nitrogen application is 125-158 kg·hm-2under normal precipitation conditions in study area can meet the growth of maize and wheat,achieve the optimization goal of ensuring yield,improving water and nitrogen use efficiency and reducing environmental pollution risks. |
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