土壤温度和含水量互作对抑制剂抑制氮素转化效果的影响

为比较生化抑制剂组合对土壤氮素转化的抑制效果,揭示不同土壤温度和含水量互作对尿素水解抑制效应的影响。该文采用室内模拟培养方法,研究土壤含水量(60%和80%田间最大持水量,water holding capacity,WHC)和土壤温度(15、25和35℃)互作对生化抑制组合N-丁基硫代磷酰三胺(N-(n-butyl)thiophosphoric triamide,NBPT)、N-丙基硫代磷酰三胺(N-(n-propyl)thiophosphoric triamide,NPPT)和2-氯-6(三氯甲基)吡啶(2-chloro-6(trichloromethyl)pyridine,CP)在黄泥田土壤中抑制氮素转化效果的影响。结果表明:土壤温度和含水量对生化抑制组合在黄泥田土壤中抑制尿素水解效应显著,以土壤温度影响更大。随着土壤温度增加,尿素水解转化增强,有效作用时间降低,硝化作用增强,脲酶和硝化抑制效应减弱;随着土壤含水量降低,尿素水解转化缓慢,有效作用时间延长,硝化作用减弱,脲酶和硝化抑制效应增强。不同土壤温度和含水量条件下,NBPT/NPPT或配施CP处理有效抑制黄泥田土壤脲酶活性,延缓尿素水解;CP或配施NBPT/NPPT处理有效抑制NH4+-N向NO_3~--N转化,保持土壤中较高NH_4~+-N含量长时间存在。新型脲酶抑制剂NPPT单独施用及与CP配施的土壤尿素水解抑制效果与NBPT相似。黄泥田土壤中生化抑制组合应用最佳的土壤温度和含水量分别为25℃和60%WHC。总之,针对不同土壤温度和含水量条件,在黄泥田土壤中应采用脲酶抑制剂与硝化抑制剂相结合的施肥方式。

Inhibition effect of inhibitors on nitrogen transformation affected by interaction of soil temperature and water content

Agricultural intensification has led to high inputs of nitrogen fertilizers into cultivated land. Addition of urease and nitrification inhibitor to fertilizers can increase N uptake and reduce N losses, but field studies have shown that their efficiency varies greatly on the environmental conditions. Soil temperature and water content are key factors controlling urea hydrolysis in soils and are also key parameters for the variation in inhibition effect of urease and nitrification inhibitors. The objective of this study was to compare the inhibition effects of biochemical inhibitor combinations on soil nitrogen transformation, and to determine the effects of different soil temperature and water content on the inhibition of urea hydrolysis. We investigated the inhibition effect of combined biochemical inhibitors (N-(n-butyl) thiophosphoric triamide, NBPT/N-(n-propyl) thiophosphoric triamide, NPPT + 2-chloro-6(trichloromethyl) pyridine, CP) on urea-nitrogen transformation as affected by soil water content (60% and 80% water holding capacity, WHC) and soil temperature (15, 25 and 35℃ ) interaction in yellow clayey soil using an 30-day aerobic incubation test. Results showed that soil temperature and water content had significant effects on the inhibition effects of inhibitor combinations in yellow clayey soil (P < 0.05), especially soil temperature. With the increase of soil temperature, urea hydrolysis increased by the effective time of the combinations reduced, and the inhibition effect of urease and nitrification weakened accompanied by increase in nitrification. With the decrease of soil water content, urea hydrolysis tended to slow by the effective time of the combinations prolonged, and the inhibition effect of urease and nitrification increased accompanied by nitrification weakened. The urease inhibition rate (Day 1) and nitrification inhibition rate (Day 30) under different soil water content treatments ranked as 60%WHC> 80%WHC, and apparent nitrification rate (Day 30) ranked as 60%WHC< 80%WHC. The urease inhibition rate (Day 3) and nitrification inhibition rate (Day 30) under different soil temperature treatments ranked as 25℃>15℃>35℃, and apparent nitrification rate (Day 30) ranked as 25℃>35℃>15℃. The urease inhibition rate (Day 3) under different biochemical inhibitor combinations ranked as U+NBPT>U+NPPT>U+NPPT+CP>U+NBPT+CP>U+CP, and nitrification inhibition rate (Day 30) ranked as U+CP>U+NBPT+CP>U+NPPT+CP>U+NPPT>U+NBPT, and apparent nitrification rate (Day 30) ranked as CK>U>U+NPPT>U+NBPT>U+NPPT+CP>U+NBPT+CP>U+CP. NBPT/NPPT or combined with CP treatments can effectively inhibit soil urease activity, and slow urea hydrolysis. CP or combined with NBPT/NPPT treatments can effectively inhibit the transformation of NH4+-N to NO3--N, and keep high NH4+-N content in soil for longer time under different soil temperature and water content conditions. Application of a new urease inhibitor NPPT alone or with CP had the similar inhibition effect of soil urea hydrolysis with that of NBPT. The optimum condition of soil temperature and water content by the application of biochemical inhibitor combinations in yellow clayey soil were 25℃ and 60%WHC, respectively. In conclusion, urea application combined with both urease inhibitor and nitrification inhibitor should be adopted in yellow clayey soil according to different soil temperature and water content conditions.