Study On Time And Spatial Change Of Nitrate Nitrogen Of Cotton And Apparent Budget Of Soil Nitrogen

The purpose of this study was to quantify the movement and distribution of nitrate in the soil profile and nitrogen uptake by crop in cotton in Nanjiang through different nitrogen fertilizer managements. Firstly we studied temporal dynamics of nitrate content in the soil solution with different nitrogen fertilizer managements in different growing period. The soil samples were obtained by drills which can take soil from deep profiles, then the nitrate leaching loss through a soil layer was calculated by quality approach, in order to point out the main periods in which lots of nitrate loss during cotton growth, Secondly we analyze the constitutes of output and uptake by cotton and yield which was caused by different fertilizer managements. Finally bring forward economical quantity of fertilizer.1,During cotton entire growing, soil nitrate content of 0-30cm soil layers trended to increase with nitrogen fertilizer rates increased, but change range of entire growing stage trended to reduce from cultivation layer to deeper soil layer. Basial nitrogen fertilizer of traditional treatment can beget leaching loss of soil nitrate before top-dressing, but top-dressing beget hardly the leaching loss because cotton assimilated large numbers of nitrogen for accelerated growing.2,Analyzing about the statistical characteristic data of soil nitrate content , the result was that the range of coefficient of variation of soil nitrate content is between 46.71% and 99.78%, in which belong to the medium-degree vitiated intensity. Spatial variability of soil nitrate content gradually increased and approached strong variability with cotton growth, which was begeted nitrogen fertilizer. The result of analysis of Sem-variance shows: transformation of soil nitrate content tally with spherical model in before seeding and after harvest, while it is line model in inchoate flowering. Soil nitrate content had relative strong spatial correlation and was more in southeast than northwest in before seeding and after harvest, while soil nitrate content hadn't spatial correlation in inchoate flowering.3. Comparing with traditional treatment, optimized treatment reduced the absorption quantity of the cotton nitrogen and enhanced agronomy and physiology utilization efficiency of nitrogen, but holding identical yield and reducing amount of nitrate nitrogen.4. In the each stage of the cotton growth remnant of soil nitrate nitrogen was higher, but loss of apparent budget of soil nitrate was higher only in the seedling stage and the beginning of bell stage. But computation of the equilibrium ratio of nitrate for the cotton entire growth indicated that the quantity fertilizer of the optimized treatment overstep the reasonable scope, too. This indicated that basal fertility was higher in the field.5.According to the result of the cotton nitrogen absorption and nitrate nitrogen remains in harvest stage, integrated soil nitrate test and the cotton growth characteristic, the reasonable quality of nitrogen fertilizer was 150kg/ hm2 under drip irrigation in Nanjiang.