Effects Of Irrigation And Nitrogen Addition On Wheat Growth In North China Plain

The rapid population increase in the world poses great challenge for food production.China has to use only 7%of the world's arable land to feed 22%of the world's population.However,due to the rapid population growth,resource shortages and environmental degradation,Chinese grain production and people's living environment are facing a great challenge and unpredictable risk.With the decline of the agricultural water and decreasing of cultivated land area,Chinese total grain production in 2050 will reduce by 14%-23%than that in 2005.In order to enhance crop grain yields,farmers often use chemical fertilizer to maintain and enhance grain yields.The statistical data showed that from 1980s to the present,crop grain yields increased by 54%,but the fertilizer inputs increased by 191%,with negative impacts on soil and water quality.Therefore,how to improve resource use efficiency is the key strategy to maintain both crop yields and environmental quality.The typical cropping system in the North China Plain(NCP)is winter wheat and summer maize rotation.The annual application rate of mineral nitrogen for conventional agricultural practices in Eastern China,Southeastern China,and NCP are now in the range of 550-600 kg N ha-1 in typical double-cropping systems.Most previous studies pay attention to irrigation and nitrogen use efficiency.However,it remains unclear how the interactions of different irrigation levels and nitrogen addition levels affect the grain yield,the farmers' income and the nitrogen use efficiency.Our experiment is located in the farm of global change ecology in Henan University in Kaifeng in Henan Province(34°49'N,114°17'E).The experiment designs different irrigation and nitrogen addition levels to examine the comprehensive effects of the wheat grain yield,farmers' income and nitrogen use efficiency.Nitrogen addition significantly reduced the soil pH(pH decreased from 8.43 to 8.20),and led to soil acidification.Irrigation suppressed the negative effects of nitrogen fertilization(P<0.05).The grain yield increased with the increasing irrigation.The grain yield was 3489 kg ha-1 under the 10 mm irrigation,which was 25.5%higher than that in 70 mm.The different nitrogen additions had marked effects on wheat grain yield,aboveground biomass and root biomass(P<0.05).The grain yield of wheat showed unimodal curve relationship.The largest grain yield was 4526 kg ha-1(300 kg N ha-1).The higher nitrogen addition controlled the effects of irrigation(P<0.05).By comparing the two growth stage of wheat grain yield,the planting density of wheat had significant effect on wheat grain yield.The irrigation promoted the income and income/expense ratio.Higher nitrogen addition could reduce the income and income/expense.Different nitrogen addition had significant effects when irrigation quantity is 50mm.The nitrogen addition level(200 kg N ha-1)of the highest income was lower than that of the highest wheat grain yield(300 kg N ha-1).Considering income/expense,the most suitable nitrogen addition was 200 kg N ha-1.The grain nitrogen content increased with the increasing of nitrogen addition,but the nitrogen use efficiency of wheat decreased with the increasing of nitrogen.There had no effects on the influences of nitrogen when the irrigation was 50 mm.This study explored the change of the North China Plain grain yield,income and nitrogen use efficiency of winter wheat with the different irrigation and nitrogen addition levels.The results showed that,considering wheat yield and farmers' income,the most efficient irrigation and nitrogen addition are 50 mm and 200 kg N ha-1.It can suppress the rate of soil acidification and nitrogen loss,but enhance the nitrogen use efficiency and maintain the ecological balance,realizing sustainable development of agricultural.