| Loessial Soil is widely distributed in the Plateau Loess, which suffered from severe soil erosion in the worldwide. Studying on soil nutrient loss is one of the most important way for the region to reduce its soil and water loss, increase agricultural production, improve the ecological environment, and increase income of farmers on the Loess Plateau. Studying on effects of fertilization treatments on nitrogen and organic matter loss in loessial soil, is beneficial to improving efficient use of nitrogen fertilizer in agricultural production, obtaining higher economic yield with less investment in agriculture field, and balancing relationship between crop nutrient needs and the reduction of environmental pollution. Based on simulation rainfall condition, this paper mainly study on characteristics of nitrogen and organic matter loss by runoff period under four kinds of nitrogen treatments., and the main conclusions are as follows:(1) The characteristics of runoff and sediment loss under different fertilization treatments showed that, fertilization can extend the initial runoff time, comparing with the CK, the initial runoff lag time of high nitrogen,medium nitrogen and low nitrogen were 5.5 times,5.2 times and 2.6 times respectively, that was, the initial runoff lag time of high nitrogen is the longest; under different fertilization treatments the runoff had the same variation trend which increased to the maximum initially, and then kept stabilize, but fell sharply at last; on the other hand, the variation trend of sediment concentration was different,which initially fell sharply, then sediment concentration was stable in remain runoff process. Furthermore, according to regression analysis of runoff and sediment accumulated loss, we found that there was a significant power function correlation between the runoff and rainfall time, while the significant linear correlation between sediment loss and rainfall time under different fertilization treatment. Comparing with the CK, increased application of nitrogen fertilizer can reduce runoff and sediment loss at varying degrees.(2) The characteristics of loss organic matter under different fertilization treatments showed that, the total variation trend of organic matter content under different fertilization treatments was similar, which sharply decreased at first, then reached the steady value when runoff time was 12 min, then, had little fluctuation; organic matter followed curves under different fertilization treatments were:: CK>low nitrogen>medium nitrogen>high nitrogen, and loss of high nitrogen was the least; However, the relationship between organic matter loss content and rainfall time under different treatments can be described by the regression equation:y= a+b Ln (x). Different fertilization had different organic matter total loss, according to regression analysis, the relationship between fertilization and organic matter loss can be described by the exponential function:T=97.2161e-0004805q.Organic matter has enrichment effect in sediment, enrichment rates under different fertilization treatments were: CK>low nitrogen>high nitrogen>medium nitrogen, and medium nitrogen had the lowest enrichment rate. So fertilization can reduce the enrichment of sediment on organic matter, but its relationship with lowering organic matter enrichment were not simple positive correlation.3) The characteristics of total nitrogen loss under different fertilization treatments showed that, the variation of the concentration of total nitrogen loss was different under different fertilization treatments, during the whole process of the rainfall, the content of total nitrogen were all follow the order of:high nitrogen> medium nitrogen>low nitrogen>CK. However, the variation of the cumulative total nitrogen loss was different from the variation of the content. Compared to the CK, the total quantity of the total nitrogen loss decreased after fertilization, which were separately 67.7%, 45.6% and 44.1%. The relationship between fertilization and total nitrogen can be described by the loss exponential equation:T=97.2161e-0004805q. Besides, there was also a correlation ship between total nitrogen loss content and rainfall time under different treatments, the logarithm correlation function of which was y= a+b Ln(x). Total nitrogen has enrichment effect in sediment, but the effect of different fertilization treatments was negative to organic matter. Furthermore, the enrichment rate of high nitrogen was significantly higher than others, while the enrichment rates of medium and low nitrogen were almost the same and that of the CK was the lowest, increased application of nitrogen fertilizer could decrease the concentration, but enhance the enrichment effect of total nitrogen.4) The characteristics of ammonium and nitrate nitrogen under different fertilization treatments showed that, the concentration of ammonium and nitrate nitrogen in the runoff under different fertilization treatments prolonged with the duration of rainfall simulation. The concentration of high nitrogen,medium nitrogen and low nitrogen decreased sharply and then went to a steady value till the end of the rainfall event. The main loss in the runoff was nitrate nitrogen, and the amount of ammonium nitrogen was little. However, there were significant linear relation between the loss of both type of nitrogen and rainfall time. The varying trend of ammonium nitrogen in sediment was decreasing to the lowest and then increasing gradually to the highest, and, at last decreasing to the primary concentration as the beginning of the runoff. While the varying trend of the nitrate nitrogen was increasing slowly to the highest, then decreasing with the rainfall time lasting. Compared to the loss of ammonium and nitrate nitrogen in the runoff, that in sediment was smaller, but both the ammonium and nitrate nitrogen under different fertilization treatments had significant logarithm relationship with rainfall time. According to regression analysis, During soil erosion process, loss style of nitrogen was mainly nitrate nitrogen which was mainly in runoff.
|
PDF Full Text Request