| Since the 1980's, following with the deterioration of resources and environmental question day by day, the environmental pollution has already caused the attention of the countries all over the world as a global serious problem. And the questions of the ecological environmental disruption and agricultural product pollution etc that caused by the pollution of the chemical fertilizer are also serious day by day, which has already become one of the restriction factors of agriculture sustainable development in the new stage. So controlling the nitrogen fertilizer eluviationing pollution, improving the utilization ratio of the chemical fertilizer, reducing environmental pollution and studying of controlling method have already become focal and important point that people study.The research of this text is divided into simulated test and field test. The simulated test mainly simulates the basic situation of the farmland, determines the content of nitrogen in soil drench solution, and adopts semi-micro Macro Kjeldahl method. The test method is to fetch the urea of the same quality and coated material of different quality first, make coating material parcel evenly the urea particle s' surface, grant them into the soil, eluviate with the distilled water every 24 hours, collect the eluviationing solution, titrate the eluviationing solution with distillation titrimetric method, that is, add alkali distillation, make the ammonia release out, absorb with boric acid solution, then titrate it with standard acid. Through the formula the content of N can be calculated in the eluviationing solution. The purpose is to determine the speed of the eluviation and release, as well as the release difference of the different mass ratio fertilizer that releases more slowly.Field test mainly examines the absorption situation of the fertilizer that releases more slowly during the growth of the crops simulated test takes Leaching Loss of the Guanzhong plain of Shaanxi province as example. The test place lies in Ba Qiao district of Xi'an., the test crop is big green vegetables.Through the experimental study from October of 2004 to March of 2005, the compare of the five kinds of materials: natural coating materials, clay , charcoal, humus, red clay, the compare of the time that postpones the nitrogen eluviationing and the analyze of the eluviationing curve, the text chooses clay and red clay as the mainresearch object. Such three kinds of coating materials as main research sulfur, borax, gypsum, etc. are mainly studied in the coated material of chemical compounds, and are compared and analyzed with the natural coating material.The eluviationing curve changes trend of different mass ratio and different coated urea resemble and the majorities all present the variation tendency of the unimodal form through the eluviationing curve's compare and analyze of different mass ratio coated urea: red clay, clay, sulfur, borax, gypsum. At the stage of about 1-15 days when the test begins, it is higher in density of N in the eluviationing solution; and then with the extension of eluviationing time, the density of N reduces gradually. According to the contrast of eluviationing time and economic cost ,etc. through analysis of variance, the best mass ratio of different coating material matching is found out: It is the best matching when the mass ratioof red clay membrane urea is 5:7,which can lengthen the eluviationing time for 11 days, reduce the nitrogen eluviationing loss by 16.12%; the amount of the clay quality has no use to lengthen the eluviationing time and the result is not obvious; when the quality ratio of urea and gypsum is 5:8,it can lengthen the eluviationing time for 8 days, reduce the nitrogen eluviationing loss by 23.86%;when the quality ratio of urea and gypsum is 5:7,it can lengthen the eluviationing time for 30 days, reduce the nitrogen eluviationing loss by 16.58% when the contrast urea N is all eluviated out ; it is the optimum matching association; When the quality ratio of the urea and the sulfur is 5:6, which is a optimum proportion ,it can lengthen the eluviationing time for 13 days , reduce the nitrogen eluviationing loss by 39.95%.Arranged by the order of the five coated materials' eluviationing time, according to the longest one: Borax >Sulfur >Gypsum >Red clay>clay, it is obvious that chemistry materials are higher than natural materials. The increasing range of the production of the crop is found in the little district test of field: the districts of gypsum coated urea >the districts of red clay >the districts which are planted with urea experimental districts of blank. It is obvious that the coated urea after dealed with obviously improves on the fertilizer efficiency. Through the measure of the N content in the soil sample from the test district, it is found that the whole nitrogen amount in the parcel fertilizer after dealed with is high 1.68-2.45 times than those which is not dealed with, this shows that the urea that is dealed with bag membrane can lengthen the fertilizer efficiency.This text is supported by natural science fund project in Shaanxi Province, and combine with actual conditions of China, choose from the coated material which is... |
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