Study On The Synergy Mechanism Of Polyaspartic Acid/Salt (PASP) In Agricultural Field

Heavy use of chemical fertilizer,aimed to improve crop yield,simultaneously caused severe results including waste of resource and environment pollution.The research and development of novel fertilizer is one of the effective methods to reduce nutrient loss.Polyaspartic acid/salt(PASP)is a biodegradable polymer material,which has been proved to favour crop growth in numerous cases.In recent years,a few studies reported that PASP application inhibited ammonia(NH3)volatilization and nitrous oxide(N2O)emission in agricultural field,reduced nitrate nitrogen(N)accumulation in soil,and limited the loss of ammonium and nitrate in leaching process.Meanwhile,molecular weight has a significant influence on the performance of PASP.Nevertheless,the study,relative to synergistic mechanism of PASP in detail,has not been reported at present.To investigate the synergistic mechanism of PASP,several experiments with respect to urease activity,exchange of cations,peanut cultivation and so on were conducted in this paper,in perspective of soil N loss,micro-mechanism as well as microelement utilization.In addition,potted rice experiment was performed to explore the contrastive application effect between PASP and other three materials to fix N(nitrification inhibitors,straw and biochar),meanwhile,analyzing the synergistic mechanism of PASP.The result data revealed that the performance of PASP on NH3 volatilization mitigation was related to its type and application rate.Conductivity test confirmed that the adsorption of PASP on cations was the reason causing less NH3 volatilization.PASP can restrain urease activity,delay the hydrolysis process of urea in soil,inhibit the transformation process from ammonium to nitrate,reduce the content of nitrite more directly beneficial to produce N2 O,and accelerate the exchange of cations in soil.PASP amendment enhanced the Olsen-P content in calcareous soil,providing the explanation on increasing phosphorus(P)uptake by crop with PASP application.Furthermore,augment of molecular weight extended the duration of PASP existed in soil,thereby gaining more obvious effect on crop yield.The potted peanut experiment in terms of amplification effect,suggested that PASP promoted the crop efficacy in utilizing microelements in soil,subsequently increasing the crop yield.The potted rice experiment confirmed that the yield and nutrients uptake of rice was boost under any N-fixed material amendment.In different vegetative periods,the superiority in the case of quality of surface water,rice growth condition,nutrients uptake and impact on soil physicochemical property,varied among various N-fixed materials.The ammonia oxidising bacteria(AOB)abundances(gene copies)was lower when these four N-fixed materials were applied.Moreover,decreased ammonia-oxidizing archaea(AOA)abundances also occurred in the treatments with PASP,nitrification inhibitors and straw application,whereas,biochar was found to aggravate the reproductivity of AOA.It is worth noting that only PASP decreased NH3 volatilization(17.22%)and N2 O emission(22.29%)in vegetative period of potted rice simultaneously.PASP was dominant in rice cultivation,incorporated with lower cost of production,biodegradable behaviour and simpler application method.