While ammonia volatilization is the main mode of nitrogen loss in paddy fields,urease inhibitors are known to effectively inhibit urease activity,delay urea hydrolysis and reduce ammonia emission.Urease inhibitors have,however,not been widely applied in paddy fields.In this study,the effects of NBPT urease inhibitor on the dynamic changes in urea hydrolysis and ammonia volatilization in wheat-straw incorporated gley paddy soils in Taihu Lake region were investigated via the dynamic chamber method.Results showed that ammonia volatilization mainly occurred during basal and tillering fertilization periods.While the highest ammonia volatilization was at basal fertilization stage,the lowest was at booting fertilization stage.Ammonia volatilization mainly occurred within three days after fertilization.Applying NBPT one day before fertilization significantly retarded urea hydrolysis,delayed occurring time and decreased value of NH+-N peak and reduced rate and amount of ammonia volatilization of surface water.After basal and tillering fertilization,urea hydrolysis ended within 2～3 days after fertilization,NH4+-N and ammonia volatilization peaks occurred on the second day under non-NBPT treatment.Peak values of NH/-N of basal and tillering fertilization were 132.3 mg·L-1 and 66.3 mg·L-1,respectively.Also ammonia volatilization peak values were 15.6 kg·hm-2·d-1 and 10.4 kg·hm-2·d-1,respectively.Under NBPT treatment,however,the peak of NH/-N occurred 4 days after fertilization after which it dropped to 70.7 mg·L--1 and then to 51.6 mg-L-1.After 4 days of fertilization,ammonia volatilization peak dropped to 4.7 kg·hm-2·d-1 and then to 2.6 kg-hm-2·d-1.Total ammonia volatilization dropped from 73.3 kg(N)hm-2 (24.4% of applied N) to 34.5 kg(N)-hm-2 (11.5% of applied N) after NBPT application,a drop of 53%.NBPT application in wheat-straw incorporated paddy fields significantly reduced ammo-nia volatilization by delaying urea hydrolysis.It was recommended that NBPT urease inhibitor could be used as nitrogen fertilizeradditive to inhibit ammonia loss in paddy fields.%氨挥发是稻田氮素损失的重要途径,为探明脲酶抑制剂NBPT对小麦秸秆还田稻田中氨挥发的影响,采用密闭室通气法,在太湖地区乌珊土上,研究了脲酶抑制剂n-丁基硫代磷酰三胺(NBPT)对小麦秸秆还田稻田中施肥后尿素水解和氨挥发动态变化的影响.结果表明:稻田氨挥发损失主要集中在基肥和分蘖肥时期.添加NBPT可明显延缓尿素水解,推迟田面水NH4+-N峰值出现的时间,并降低NH4+-N峰值,降低了田面水氨挥发速率和挥发量.NBPT的效果在基肥和分蘖肥施用后尤为明显,不加NBPT时施入的尿素在2～3 d内基本水解彻底,NH4+-N和氨挥发速率在第2d即达到峰值,两次施肥后NH4+-N峰值分别为132.3 mg·L-1和66.3mg·L-1,氨挥发峰值为15.6 kg·hm-2·d-1和10.4 kg·hm-2·d-1;而添加NBPT后,NH4+-N峰值推迟至施肥后第4d出现,NH4+-N峰值降至70.7 mg·L-1和51.6 mg·L-1,氨挥发峰值降至4.7 kg·hm-2·d-1和2.6 kg·hm-2·d-1.添加NBPT使稻田氨挥发损失总量从73.3 kg(N)·hm-2(占施氮量的24.4％)降低至34.5 kg(N)·hm-2(占施氮量的11.5％),降低53％.在添加小麦秸秆稻田中添加NBPT通过延缓尿素水解而显著降低了氨挥发损失.
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