Simulation Of Nitrate Leaching And Influencing Factors In Topsoil Under Plastic Film Mulched Cultivation In Danjiangkou Reservoir Area

The Middle Route Project of South-to-North Water Diversion is of great significance to mitigate the severe situation of the shortage of fresh water resources in North China.As the source area of the important drinking water protection area and the Middle Route Project of the south to North Water Diversion Project,after treatment of point source pollution in the reservoir area,Non-point source pollution has become a potential threat to the water quality of the water source.Because of the large area of Danjiangkou reservoir and farmland,Water and soil erosion and agricultural non-point source pollution are still more prominent.Film mulching,as a simple and convenient farming method,is widely used in the farmland of the reservoir area,however,the mechanism of its impact on agricultural non-point source pollution remains to be clear.Compared with non-mulching cultivated land,field experiment explored the change characteristics of soil temperature,soil water and soil nitrogen under film mulching in Wulongchi small watershed during maize growing period.The correlation and the single factor fitting and the two factor nonlinear simulation between the nitrate nitrogen leaching loss and the influence factors were made.The results showed that:(1)During the first three stages of Maize,the amounts of film mulching soil N03-N leaching were higher than those with non-mulching by 1.7%.During the different growth stages of Maize,film mulching reduced the NO3-N leaching at the seedling stage,but could increase the NO3-N leaching at heading stage and jointing stage.(2)The film mulching increased soil NO3-N content by 33.70%,6.92%and 23.57%compared to non-mulching in 0-10cm,10-20cm and 20-30soil layer.During the different growth stages of Maize,film mulching reduced soil NO3-N content in 0-20cm soil layer at the seedling stage,but could increase soil NO3-N content at heading stage and jointing stage.(3)During the growth stages of Maize,compared with non-mulching,film mulching could increase the soil temperature 1.1 ? in 0-30 cm soil layer,and increase temperature 1.8? in 0-10cm soil layer.During the different growth stages of Maize,the increase of temperature at the seedling stage was the most obvious,and Maize seedlings can be protected from the the low temperature.With the growth of Maize,the increase of temperature on film mulching gradually decreased.Because of better growth of Maize,the soil temperature in the later stage of maize growth was lower than non-mulching treatment.Film mulching could increase the soil temperature of 0-30 cm soil layer at the seedling stage,and it had better insulation effect at night.(4)During the growth stages of Maize,film mulching reduced the soil water storage 2.34mm,1.38mm in 0-10 cm and 10-20cm soil layer,and the film mulching could reduce stability of water storage,but could increased the water storage and stability in 20-30 cm soil layer.Through the change of soil temperature in different growth stages of 0-10cm soil layer,film mulching reduced the water storage in seedling stage,but there is little difference from the non-mulching at heading stage and jointing stage.(5)The relationship between the 11 soil NO3-N leaching and the influence factors of tow treatment in 0-10cm soil layers showed that:There is a significant positive correlation between antecedent precipitation,soil water storage,soil temperature and soil nitrate leaching loss.It means that the risk of nitrate leaching is increased with the increase of rainfall,soil temperature and soil water storage.Nevertheless,a large amount of nitrate nitrogen leaching would reduce the accumulation of nitrate nitrogen in the soil.The single factor simulation results of soil nitrate leaching loss and the influence factors showed that the loss of nitrate nitrogen leaching in the non covered soil was higher than that of the early rainfall and the soil nitrate nitrogen content,and the nitrate leaching loss in mulched soil was higher than the soil water storage and soil temperature.Furthermore,two factor nonlinear simulation of soil nitrate nitrogen leaching in plastic film mulching and no plastic film mulching was carried out.The fitting results of R2 were 0.910 and 0.817,respectively,and the fitting results were good.