Loss Characteristics Of Nitrogen And Phosphorus Of Cow Dung And Soil Under Simulated Rainfall Conditions

Livestock and poultry manure pollution is the most important part of rural non-point source pollution.By means of artificial rainfall simulator,under different rainfall intensity and different rainfall conditions to study the loss of rainfall runoff nutrient characteristics and loss estimation of the open-air pile of cow dung,in order to provide practical basis for the reasonable disposal of livestock and poultry manure,and make contribution to reduce rural non-point source pollution at the same time.Through the experiment,gain the following results:（1）Generation of initial runoff is mainly controlled by rainfall,rainfall intensity on its influence was not significant,when the rainfall reached the cow dung or soil saturation moisture capacity,the runoff started to produce.Usually,cow dung itself water content is high（92%）,when the rainfall is around 4 mm there will have the initial runoff;when water content is around 50%,the rainfall around 15 mm will have runoff generated;when the water content is very low（2-3%）,usually the initial runoff generated around 20 mm rainfall.（2）In the same rainfall,under the condition of different rainfall intensity,no matter is cow dung or soil,the characteristics of its monitoring nutrient index（except TP）with the loss of rainfall runoff are roughly the same trend.;the change of concentration of TN,NH₄⁺-N,NO₃^--N are similar,and the concentration characteristics of COD is obviously"peaks"type;The loss of TP concentration characteristics under different rainfall intensity,show differently:in the heavy rain,the fresh cow dung concentration characteristics of TP reached the highest when the initial runoff period,and then slow down with the rainfall-runoff process continues,and in the light rain and moderate rain case,showing slowly rising at the initial stage of runoff,and soon appear a peak concentration at about 30 mm rainfall;the concentration characteristics of manure cow dung of TP appear rise firstly than down in light rain,in the heavy and moderate rain showing up and down fluctuation;The concentration of soil TP loss is fluctuation and rise obviously when the rain is strong,and in light and moderate rain intensity,concentration rising constantly,in 80 mm show the peak concentration.（3）1t cow dung in a 120 mm rain,the loss amount of nitrogen,phosphorus and chemical oxygen demand accounted for the proportion of the original content of the cow dung were 0.3%,0.13%and 0.18%.The loss amount of 1t soil of nitrogen,phosphorus,COD accounted for 0.75%,0.11%,0.049%of original content respectively under different rainfall intensity;In the 10mm,25mm,50mm rainfall process,phosphorus loss quantity of fresh cow dung and maturity cow dung phosphorus accounted for original content of cow dung in 0.044‰,0.130‰,0.310‰and 0.000‰,0.043‰,0.270‰;nitrogen loss accounts for the proportion were 0.069%,0.150%,0.240%and 0.000%,0.037%,0.15%;the loss of COD occupies the proportion of organic matter were 0.032%,0.079%,0.120%and0.000%,0.009%,0.039%.The loss form of fresh cow dung is mainly NH₄⁺-N and NO₃^--N,accounted for 9.6%,32.5%and 13.4%,29.1%and 12%,27.8%of total loss in 10mm,25mm,and 50mm rainfall processes,respectively.Maturity cow dung nitrogen loss form was mainly NO₃^--N,in the rainfall of 25 mm and 50 mm accounted for 81.3%and 85.1%of total loss amount,respectively.（4）The amount of livestock manure in Yong an Jiang basin was 24.88million tons a year,converted to total nitrogen,total phosphorus,organic matter content was 5270 tons,2184.40 tons and 13.17 million tons,respectively.In the year of rainfall,the loss amount of nitrogen,phosphorus and organic matter is 113.020 tons,7.355 tons,706.370 tons respectively,accounting for 2.14%,0.34%,0.54%of the total content.