Response Of Soil N Transformation And Nitrous Oxide Emission To Nitrapyrin And NBPT On Drip Irrigated Calcareous Soil

【Objective】Urea with urease inhibitor and nitrification inhibitor play a significant role for improving Nfertilizer utilization efficiency and mitigating soil nitrous oxide emission in calcareous soil under dripirrigation of Xinjiang provience.A soil culture experiment was carried out to screen out the optimal kind ofurease inhibitors of n-(n-butyl) thiophosphoric triamide (NBPT), ammonium thoisulfate(ATS) and gossypolacetate(GA), and meanture the best proportion ratio of nitrification inhibitor/urease inhibitor to study theeffect of nitrogen transformation. Furthermore,a field experiment was carried out to study the response ofurease inhibitor and nitrification inhibitor on soil nitrogen transformation,soil N2O emission and N uptake,and nitrogen use efficiency for wheat under drip irrigation.Also,we could provide a knowledge theoreticallyon how to improve N fertilizer utilization efficiency and spread the application of urease inhibitor andnitrification inhibitor under drip irrigated field.【Method】In the present research, a soil culture experiment was carried out to study the effects of threedifferent kind of urease inhibitors of n-(n-butyl) thiophosphoric triamide (NBPT), ammonium thoisulfate(ATS) and gossypol acetate(GA) on urea hydrolysis dynamics, soil ammonium and nitrate transformationin greenhouse condition. Soil N2O concentration variation characteristic was also determined usingUnisense N2O micro-sensor in situ method; Comparison the effects of nitrapyrin with three concentrationsof NBPT on soil nitrogen transformation,it is basis to screen out the optimal proportion ratio of nitrificationinhibitor/urease inhibitor in calcareous soil; A field experiment was carried out to study the effects ofnitrapyrin with n-(n-butyl) thiophosphoric triamide (NBPT) on urea hydrolysis dynamics, and on wheat dryweight, wheat yield, N uptake, and nitrogen use efficiency, meanwhile use the static chambers with gaschromatography method to study on the N2O emission.【Result】1) Urea hydrolysis process has been obviously inhibited with NBPT, ATS and GA amendment, theeffect of different urease inhibitors on soil urea hydrolysis was: Urea+NBPT＞Urea+GA＞Urea+ATS.The NBPT had the highest urea inhibition rate with33.6%. And an obvious decreasing trend observedon using urease inhibitors, the effect of different urease inhibitors on soil N2O concentration was: Urea+NBPT＞Urea+ATS＞Urea+GA.2)10‰NBPT kept the high efficiency in14days, and its urea inhibition rate arrived to51%. Afterapplication soil NH4+-N content till rise up to peak value on the7th,14th,21thday, respectively. And NO3--Ncontent obvious increasing trend observed during soil culture period. Urease inhibitor combined withnitrification inhibitor of5‰and10‰NBPT+Nitrapyrin plays an important role on inhibiting ureahydrolysis and nitrogen transformation, increasing soil nitrogen contents in calcareous soil3) Urea+Nitrapyrin+NBPT treatment could markly inhibited urea hydrolysis, and after3days withurea supply, compaired with urea the soil NH4+-N content was decreased by47.6%and61.3%, then after 7days with urea supply, compaired with urea the soil NH4+-N content was increased by55.6%and38.1%on heading and filling stage of wheat, respectively.The soil NO3--N content was inhibited byUrea+Nitrapyrin+NBPT treatment, and the NH4+/NO3-ratio was increased.4) Soil urease activity was inhibited by Urea+Nitrapyrin+NBPT treatment, and comparied with ureawas decreased by14%and25%on heading stage and filling stage of wheat.And hydroxylammoniumreductase activities show that:CK＞Urea＞Urea+Nitrapyrin+NBPT; the nitrite reductase activity show that:Urea＞Urea+Nitrapyrin+NBPT＞CK; Urea+Nitrapyrin+NBPT treatment was significantly higher thanurea and CK treatments on nitrate reductase activity. The microbial struetural of ammonia oxidizingarchaea amoAaffected by application of Urea and Urea+Nitrapyrin+NBPT treatments, and compaired withurea treatment the genetic diversity was decreased.5) The N2O flux obvious increasing trend observed during the days after drip irrigation:1stday＞the5th＞7th. With urea applied had the higher N2O flux in the heading and filling stage of wheat, and compairedwith urea treatment the N2O flux was decreased by38%,42.7%,54.7%and57.8%,45.8%,46.7%withUrea+Nitrapyrin+NBPT treatment.6) Urea+Nitrapyrin+NBPT was application on wheat could improved wheat dry weight, N uptake, andnitrogen use efficiency, and grain,1000-grain weight was increased,enhanced the wheat yield.【Conclusion】1) NBPT, ATS and GAplay important role on inhibiting urea hydrolysis and decreasing soil N2Oemission, the effecncy on inhibited urea hydrolysis process was: NBPT＞GA＞ATS. Urease inhibitorof NBPT with2‰,5‰,10‰combined with Nitrapyrin plays an important role on inhibiting ureahydrolysis, soil ammonium and nitrate transformation.5‰and10‰NBPT with Nitrapyrin had a moreeffiency inhibition on nitrogen transformation.5‰NBPT with nitrapyrin can be regarded as a promisingcombination inhibitor.2) Urea+Nitrapyrin+NBPT treatment could markly inhibited urea hydrolysis, and the NH4+/NO3-ratiowas increased, the nitrogen transformation was decrease，and the N2O flux was decrease byUrea+Nitrapyrin+NBPT treatment on the heading and filling stage of wheat.3) Soil urease activity was inhibited and hydroxylammonium reductase activities and nitrite reductaseactivities were decreased by urea+Nitrapyrin+NBPT treatment, whereas, improved the nitrate reductaseactivity. The microbial struetural of ammonia oxidizing archaea amoA affected by application of Urea andUrea+Nitrapyrin+NBPT treatments, and compaired with urea treatment the genetic diversity wasdecreased.4) Urea+Nitrapyrin+NBPT was application on wheat could improved wheat dry weight, N uptake, andnitrogen use efficiency,and grain,1000-grain weight was increased,enhanced the wheat yield.