Synergistic Effect Of Enhencers And PAM On Mechanism Of Nitrogen Losses And Transfer For Control Of Agricultural Non-point Pollution

From "the source control" and PAM in improving soil structure,as a basic strategy,through adding different fortifiers make the PAM and fortifiers work together.This research tried to synchronously improve the soil structure effectively,fix surface,reduce runoff and make nitrogen and phosphorus to retain in the soil at maximum so that operating the crops-soil nutrient circulation system more effective.In indoor physical chemistry experiment,by means of simulation experiment flooded,soil column simulation experiment and artificial rainfall slope runoff nitrogen test,it researched PAM and fortifier's joint action on soil nitrogen migration,transformation and leaching effecting.In the circumstances without changing current agricultural production pattern,there is no need for much more investment and construction.Meanwhile from this research,it selected and illustrated the best combinations of fortifier and PAM,explored a more efficient,economical and practical control technology to control agricultural non-point source pollution,and found a effective way to protect the safety of Chongqing's water environment.Furthermore It has important theoretical and practical significance due to three gorges reservoir.The main conclusions of research are:(1)PAM clearly affected the adsorption of NH⁴⁺-N in soil.PAM could improve the adsorption of ammonium on soil,however PAM and fortifier could enhance its adsorption capacity.The size and orientation and species has close relationship to sort of fortifier.Besides lime,the other fortifier's adsorption capacity could increase 37.5%-83.3%with comparison of PAM,differences are significant(p＜0.05).By using PAM and fortifier,the main influence on the adsorption capacity of ammonium in slow adsorption stages.PAM joint zeolite and citric acid had best adsorption, compare with PAM,average adsorption increased 34.1%and 20.6%respectively,maximum adsorption increased 51.7%and 83.3%respectively.The equation of Longmuir,Freundlich and Temkin all were used to reflect the reaction all-right fitting.Although PAM can increase the adsorption of nitrogen in the soil,but holding capacity of nitrogen decreased.Add fortifiers can compensate for this defect.Zeolite had the best effect,the average desorption rate reduced by 21.3%, significant difference(p＜0.05),compared with the all blank control(CK).In flooded simulation,the soil after PAM and fortifiers combined treatment could restrain the rate of ammonium converse to nitrate nitrogen.And make nitrogen release quickly to reach to the dynamic balance,meanwhile make water TN concentrations in a relatively stable concentration level. Citric acid can be not only applied to restrain ammonium converting to nitrate nitrogen,but also restrain TN obviously.In the first four days after the flood,TN concentrations reach maximum peak 85.27μg/ml.After that,it had continued declining to end of the test,the amount of releasing nitrogen in covering up water was 14.13μg/ml,which is lower than 16.96μg/ml of all blank control.(2) The soil treating by PAM and fortifier,it had an obvious affection of nitrogen's migration and leaching in soil.The treatment effect is related to the sorts of fortifiers.Straw stalk and alkaline straw with PAM combination controlled the soil nitrogen loss significantly.Gypsum and zeolite combined with PAM respectively,had certain effects too.But this effecting revealed in the late leaching gradually,the joint action in early process was not obvious.The soil after treatment of the straw stalk with PAM and alkaline straw with PAM could obvious restrain the loss of ammonium and nitrate nitrogen,the accumulated leaching amount of ammonium-N reduced 15.1%and 30.3%,compare with single PAM application,there were significant differences.The accumulation leaching amount of nitrate were reduced25.5%and 38.4%, compared with single PAM application with a significant difference.The soils after treatment by PAM joint with gypsum and zeolite respectively can not well controlled the loss of ammonium-N, and its effect was mainly manifested in the control of nitrate,two leaching cumulative amount of nitrate were reduced 16.5%and 14.4%.As to the total nitrogen leaching,all the accumulated leaching quantity except phosphor gypsum were less than CK.Straw,alkalize straw,gypsum and zeolite,these 4 cumulative leaching quantity of ammonium-N reduced 27.9%,10.6%,18.2%and 10.4%,respectively.Dealing with straw stalk and alkaline,the differences are also significant(p＜0.05).(3) To the runoff loss of nitrogen,the useage of PAM and fortifier had good effects,and with a significant relationship with the slope and rainfall intensity.When the slope is 15°,rainfall intensity is 33.7mm/h,different kinds of fortifier(Zeolite,citric acid,straw) and PAM can effectively reduce the loss of runoff nitrogen,it effected by vary sorts of fortifier.It was better after adding fortifier than just only control by PAM.The effects of Zeolite alkalize straw and citric acid separately combined with PAM reduces 33.7%,57.1%and59.7%repectively in comparison with single PAM application.Therefore,by adding fortifier PAM can control nitrogen losses in soil well,which indicated a positive role.And the citric acid controlled the losses of ammonium and nitrate nitrogen the best,the twice average rainfall of soil ammonium-N loss rate was 0.375 mg/min,reduced 70.6%, when compared with the single PAM.The twice average rainfall of soil nitrate-N loss rate was 1.56 mg/min,reduced 53.5%,when compared with the single PAM.In addition,alkalize straw also had very good effect on controlling the loss of nitrate nitrogen.The twice average rainfall of soil nitrate-N loss rate was 1.53 mg/min,reduced 54.4%,when compared with the single PAM.When the rainfall intensity was 33.7mm/h,the dosage of PAM was 8g/m²,alkalize straw was 300g,which meant the slope influences the losses of soil nitrogen.When the slope is low,the effecting combined with PAM and basification straw of the loss of soil ammonium-N is small.With the increasing slope,its influence has revealed.The loss of nitrogen in different slope were 8°(1.23 mg/min)＜15°(1.53 mg/min)＜20°(2.39 mg/min).The higher slope,the loss of nitrate is more serious.In addition,with the increasing of slope,total erosion of nitrogen was increasing.When the slopes were 15°and 20°,the losses increased 1.75%and 87.1%repectively in comparison with 8°.And thus the increases of slope have a bad effect of controlling the losses nitrogen while PAM combined with basification straw application.When the slope was 15°,the dosage of PAM was 8g/m²,alkalize straw is 300g,the different rainfall intensity influence to the amount of the nutrient losses by runoff.The twice rainfall on the base of PAM and alkaline straw,the whole loss rate of NH⁴⁺ - N is gentle.It showed that PAM can make the soil surface keep NH⁴⁺ which can slow leaching with rainfall.The heavy rainfall intensity in twice rainfall can keep the loss of ammonium-N at high levels.In the twice rainfall,the loss rate of NH⁴⁺ - N was:heavy rain(0.47 mg/min)＞moderate rain(0.78 mg/min)＞little rain(0.65 mg/min).Alkalize straw with PAM could control the loss of ammonium-N loss well in the little rain. The rainfall intensity has certain effecting on nitrogen erosion.When the rainfall intensity is bigger, the ammonium-N is more erosion than nitrate nitrogen.Overall,rainfall intensity can influence the losses of nitrogen,when alkalize straw and PAM combined.The bigger rainfall intensity,the more beneficial to nitrogen loss,furthermore ammonium -N is easier loss than nitrate nitrogen.When adding fortifier,initial runoff time with nitrogen was all in advance.The citric acid had the most obvious effect.With the increasing of the slope,initial runoff time with nitrogen slightly advanced,and the differences were small.When rainfall intensity increased,the time of the initial mnoffis also in advanced.