Study On Nitrogen Loss Characteristics Of Runoff In Typical Purple Soil Slope

Nowadays,soil erosion is a serious environment problem and more and more scholars start to pay close attention to this world-level problem.Soil erosion not only causes the loss of soil&water and soil nutrition,but also leads to eutrophication of waters because nutrition from soil flows into the waters.The main tillage soil of hilly area in Sichuan is purple soil,which is shallow and weathering.In addition,the heavy rainfall concentrates on Sichuan's hilly area in summer,which is extremely easy to cause soil erosion from slope cropland of purple soil.Nitrogen from farmland flows into the water,which will increase the risk of eutrophication.Experiments of this study were carried out on a 7?slope cropland of purple soil under natural rainfall conditions and in the case of non-fertilization treatment.This study investigates under different rainfall conditions the erosion characteristics of CK,NPK,OM,OMNPK,RSD and RSDNPK,Main conclusions of the study are as follows:?1?.Under different treatments of fertilizer,the runoff yield of surface runoff is:CK>OM>NPK>OMNPK>RSDNPK>RSD.Compared single chemical fertilizer with manure with chemical fertilizer,the amount of runoff of the latter one is lower than single chemical fertilizer,from which is related to soil infiltration rate is raised by improving the agglomeration structure of soil.The amount of surface runoff of Straw Returning is the least and it is related to the soil porosity.The sediment production of surface runoff is:CK>OM>NPK>OMNPK>RSDNPK>RSD.The runoff amount of silt of NPK?OM?OMNPK?RSD?RSDNPK were reduced by 61%,50%,70%,95%and 87%respectively than CK.Therefore,RSD treatment can protect soil and water better than other treatments.?2?.Heavy Rainstorm?on July 18?produced more sediment than rainstorm?on13 July?and heavy rain?on 9 August?.This indicates that the higher the precipitation,the more loss amount of sedimentation was.By using regression analysis method with rainfall and the quantity of sediment,the author found that the rainfall and sediment yield are linearly dependent.The Equation is:y=ax+b?a>0?,it is significantly correlated between rainfall and lost sediment under NPK,OM and OMNPK.?3?.The average value of TN concentration on surface runoff is:OM>RSD>RSDNPK>OMNPK>NPK>CK.Compared with no fertilizer treatment,the TN concentration of NPK?OM?OMNPK and RSDNPK were up by 35%,35%,43%,47%and 47%.The average value of TDN concentration of surface runoff is:OM>RSDNPK>RSD>OMNPK>NPK>CK.Compared with no fertilizer treatment,the TN concentration of NPK?OM?OMNPK?RSD and RSDNPK were up by 34%?59%?44%?52%and 52%.The average value of NO₃^--N concentration is:OM>RSDNPK>OMNPK>RSD>NPK>CK.Compared with no fertilizer treatment,the NO₃^--N concentration of NPK?OM?OMNPK?RSD and RSDNPK were up by respectively 46%?70%?64%?62%and 65%.The average value of NH₄⁺-N concentration is:OM>CK>NPK>RSDNPK>OMNPK>RSD.Compared with no fertilizer treatment,the NH₄⁺-N concentration of NPK?OM?OMNPK?RSD and RSDNPK were reduced 3%?8%?9%and 4%,OM treatment was 5%higher than CK treatment.?4?.The TN concentration of each fertigation treatment in the interflow is:OMNPK>OM>NPK>RSDNPK>RSD>CK.Compared with no fertilizer treatment,the TN concentration of NPK?OM?OMNPK and RSDNPK were up by 72%?72%?81%and54%;TheconcentrationofTDNisasfollows:OMNPK>NPK>OM>RSDNPK>CK>RSD.Compared with no fertilizer treatment,the TDN concentration of NPK?OM?OMNPK and RSDNPK increases by 70%?70%?74%and 53%,The TDN concentration of RSD was reduced by 2%.The concentration of NO₃^--N is in turn:OMNPK>NPK>OM>RSDNPK>CK>RSD.Compared with no fertilizer treatment,the NO₃^--N concentration of NPK?OM?OMNPK and RSDNPK were up by 7%?68%?71%and 51%,The NO₃^--N concentration treated by RSD was12%lower than that of CK.The concentration of NH₄⁺-N is:RSDNPK>NPK>OM>OMNPK>CK>RSD,Compared with no fertilizer treatment,the NH₄⁺-N concentration of NPK?OM?OMNPK and RSDNPK were up by 24%?15%?8%and 25%??5?.ThefluxofTNlossinsurfacerunoffis:CK>OM>RSD>OMNPK>NPK=RSDNPK.The TN loss flux of NPK?OM?OMNPK?RSD and RSDNPK were lower than that of non-fertilization.The flux of TDN loss is:OM>RSD>CK>OMNPK>RSDNPK>NPK.Compared with no fertilizer treatment,the TDN loss flux of NPK?OMNPK and RSDNPK were reduced by 44%?33%and33%,OM and RSD were up by 34%and 34%.The flux of NO₃^--N loss is:OM>RSD>RSDNPK>OMNPK>CK>NPK.The NO₃^--N loss flux of NPK was lower than CK.The NO₃^--N loss flux of OM?OMNPK?RSD and RSDNPK were up than thatofCKandNPK.ThefluxofNH₄⁺-Nlossis:CK>RSD>OM>NPK>OMNPK>RSDNPK,Compared with no fertilizer treatment,the NH₄⁺-N loss flux of NPK?OM?OMNPK?RSD and RSDNPK were reduced 69%?68%?75%?63%and 76%.?6?.Flux variation range of flow TN?TDN?NO₃^--N and NH₄⁺-N in interflow is0.58-9.31 kg·hm^-2,0.69-7.96 kg·hm^-2,0.60-7.11 kg·hm^-2 and 0.01-0.04 kg·hm^-2.The loss flux of TN?TDN and NO₃^--N vary in a large range,and the loss flux of NH₄⁺-N is little.Compared with no fertilizer treatment,the TN?TDN?NO₃^--N and NH₄⁺-N loss flux were up.Compared with NPK,it can effectively reduce that loss flux of TN,TDN,NO₃^--N and NH₄⁺-N in the middle flow of the soil.?7?.In surface runoff,The NO₃^--N/DP of all fertilizer treatment were higher than the upper risk limit.Compared with the rate of Inorganic-N/DP and NH₄⁺-N/DP,we can find,the risk of eutrophication was more likely to occur of CK,NPK and OM.The eutrophication risks of OMNPK,RSD and RSDNPK were lower.The Inorganic-N/DP and the NO₃^--N/DP of all fertilizer treatment were higher than the upper risk limit in the interflow.Compared with NH₄⁺-N/DP,the the upper risk limit of CK and OM was lower.NPK,OMNPK,RSD and RSDNPK have a higher probability of contamination of farmland surface source.