Effects Of Different Rainfall Intensities And Fertilization On Nitrogen And Phosphorus Leaching In Southern Hebei

Nitrogen（N）and phosphorus（P）leaching is an important way of agricultural non-point source pollution.It will not only cause the waste of fertilizer,but also produce environmental problems such as surface water eutrophication,groundwater pollution and soil physical and chemical properties deterioration.Therefore,it is urgent to control nitrogen and phosphorus leaching.Taking farmland sandy loam in Southern Hebei as the research object,using artificial simulated rainfall test method,this thesis carried out an experimental study on the influence of the combination of fertilization and rainfall intensity on nitrogen and phosphorus leaching loss in the soil-water system,analyzed the influence of different fertilization treatments（Control check,CK;Conventional fertilization,CF;Conventional fertilization+biochar,CFB;Conventional fertilization+zeolite,CFZ）on the vertical distribution of soil water and nutrients,and the relationship between nitrogen and phosphorus leaching and rainfall intensity,seepage flow,fertilization and the addition of soil conditioner（biochar or zeolite）was established,the countermeasures to reduce the leaching loss of nitrogen and phosphorus in farmland are put forward,which provides a theoretical basis for effectively controlling agricultural non-point source pollution in Southern Hebei.The main conclusions are as follows:Firstly,under rainfall conditions,soil nutrient content decreased with depth,while soil moisture content increased with depth.Fertilization（CF）could significantly increase the contents of alkali hydrolyzable nitrogen,available phosphorus and available potassium,but had no significant effect on the content of soil organic matter and water content.Compared with CF,the average alkali hydrolyzable nitrogen,available phosphorus,available potassium,organic matter content and surface water content of soil added with biochar group（CFB）increased by 12.11%,5.08%,2.35%,6.32%and 8.71%respectively;the average contents of alkali hydrolyzable nitrogen,available phosphorus,available potassium and surface water content of soil added with zeolite group（CFZ）increased by 8.41%,13.13%,2.60%and 8.42%respectively.Secondly,Under the same fertilization treatment,there was a positive correlation between rainfall intensity and the cumulative leaching loss of ammonia nitrogen（AN）,nitrate nitrogen（NN）,dissolved nitrogen（DN）and available phosphorus（AP）,that is,L_30mm·h-1>L_20mm·h-1>L_10mm·h-1.The initial seepage flow and total seepage volume in11h are V_30mm·h-1>V_20mm·h-1>V_10mm·h-1.Under the same rainfall conditions,compared with the control group（CK）,CF treatment increased dissolved nitrogen leaching by188.86%～196.65%and available phosphorus leaching by 222.09%～238.54%.Compared with CF,the application of biochar can reduce 6.09%～8.31%seepage flow,50.21%～67.92%dissolved nitrogen leaching loss and 27.62%～41.35%available phosphorus leaching loss.The application of zeolite can reduce 3.57%～6.94%seepage flow,43.50%～65.51%dissolved nitrogen leaching loss and 20.95%～36.60%available phosphorus leaching loss.Thirdly,there was a significant linear correlation between cumulative leaching loss of N,P and seepage flow（R²>0.91,p<0.001）,and the goodness of fit was ammonia nitrogen>dissolved nitrogen>nitrate nitrogen>available phosphorus.There is also a mathematical relationship between rainfall intensity and seepage flow and the total leaching loss of N and P,which can be expressed by natural logarithm and linear equation respectively.Correlation analysis showed that infiltration rate and fertilization were the main factors affecting N and P leaching,rainfall intensity was an important factor,and biochar and zeolite played a strong role in controlling N and P leaching.In practice,in order to reduce the leaching loss of N and P from farmland and reduce agricultural non-point source pollution,controlling the seepage flow and the amount of fertilizer is the key.Reducing the generation of seepage,improving the soil water and fertilizer conservation and reducing the application of chemical fertilizer are important means to effectively control non-point source pollution.