Effects Of Water And Nitrogen Application On Yield,Water And Nitrogen Utilization Of Winter Wheat And Summer Cotton

For solving the unreasonable application of water and nitrogen fertilizer in winter wheat-summer cotton system in the Huang-Huai-Hai Plain,a field experiment was carried out to investigate effects of nitrogen and irrigation on crop growth,yield,and water and nitrogen use efficiency,and to develop a high efficiency water and nitrogen management with high yield and less nitrogen loss in the winter wheat-summer cotton system.Two factorial treatments were arranged in the split plot design.The main plots included 5 nitrogen fertilizer levels（the nitrogen fertilizer rate of 0,120,180,240,300 kg/hm² for winter wheat,and 0,60,120,180,240 kg/hm² for summer cotton,referred to N0、N1、N2、N3、N4）as one factor and the sub plots included 3 irrigation levels（the irrigation quota of 40,30,20 mm for winter wheat,and 30,22.5,15 mm for summer cotton,referred to I1、I2、I3）as another factor.There were 15treatments with three replications.The main results were as follows:（1）Plant height and leaf area index（LAI）of winter wheat and summer cotton were significantly increased with the increasing nitrogen fertilizer application from N0 to N3.However,LAI of winter wheat and summer cotton decreased when the nitrogen fertilizer rate was higher than N3.Plant height and LAI increased with the increase of irrigation amount,and the maximum values was investigated in I1.The specific leaf weight of summer cotton and the SPAD of wheat flag leaf increased with the increase of nitrogen fertilizer rate from N0 to N3,while the specific leaf weight of summer cotton decreased when the nitrogen fertilizer rate was higher than N3.Increasing irrigation amount could significantly improve the flag leaf area of winter wheat,but decrease the specific leaf weight.（2）Irrigation wate and nitrogen application rate improved significantly the above-ground biomass and yield of winter wheat and summer cotton.When the application rate of nitrogen fertilizer was less than N3,increasing nitrogen fertilizer rate may increase effectively the above-ground biomassand yield,and it affected adversely biomass and yield when the nitrogen fertilizer rate exceeded the N3 level.With same nitrogen application rate,wheat and cotton yield increased with increasing irrigation quota.The maximum yield of 8034 kg/hm² for winter wheat and 4016 kg/hm² for summer cotton was measured both on treatment N3I1（i.e.nitrogen fertilizer rate 240 kg/hm² and irrigation quota 40mm for winter wheat,and nitrogen fertilizer rate 180 kg/hm² and irrigation quota 30mm for summer cotton）.（3）Rising nitrogen fertilizer rate could improve amino acid content,drop value and wet gluten value,but drop value decreased when nitrogen fertilizer rate was greater than 180 kg/hm²,and the amino acid content decreased when the nitrogen fertilizer application rate exceeded the rate of 240kg/hm².Under same nitrogen fertilizer application rate,water deficit was beneficial to the increase of amino acid content,drop value and wet gluten value.Effect of nitrogen application rate on the lint percentage was also extremely significant.The increase of N application rate reduced the lint rate of summer cotton.Water and nitrogen application rate had no significant effects on quality of cotton fiber.（4）Under same irrigation rate,increasing nitrogen fertilizer application rate could significantly increase nitrogen content of stem and leaf,N uptake by stem and leaf,and total N uptake by shoot.At same nitrogen application rate,the nitrogen content of straw,N uptake by straw and total N uptake by shoot increased significantly with increase of irrigation quota in winter wheat,while the nitrogen content of straw,nitrogen uptake by straw and total N uptake by shoot decreased in summer cotton.（5）The NO₃^--N content of soil profile at harvesting increased with rising nitrogen fertilizer application rate,and the maximum was measured in the treatment with the nitrogen fertilizer rate of N4.The accumulation of NO₃^--N was mainly concentrated in the 0⁴0cm soil layer.The accumulation of NO₃^--N in different soil layers was affected by the nitrogen fertilizer application rate,and the accumulation area of NO₃^--N moved downward with the increase of nitrogen application rate.Increasing nitrogen fertilizer rate could effectively improve the soil mineral nitrogen content at harvesting.The apparent nitrogen loss of summer cotton increased remarkablely with increasing nitrogen application rate,but there was not similar treadment in winter wheat.（6）Performance of different irrigation and nitrogen treatments in different hydrological years in Xinxiang region was simulated with the DSSAT model.It was concluded that the nitrogen application rate of 180²40 kg/hm²,the lower limit of irrigation of 40%of the available soil water content and the irrigation quota of 30 mm could be used as the optimal water and nitrogen management for drip-irrigated winter wheat in Xinxiang region.