脲酶抑制剂对石灰性土壤尿素转化及N_2O排放的影响

Responses of Urea Transformation Dynamics and Nitrous Oxide to Three Urease Inhibitors in Calcareous Soil

通过研究脲酶抑制剂对土壤中尿素转化的影响,揭示土壤各形态氮对N2O的贡献,为控制石灰性土壤氮素损失及提高氮肥利用率提供理论依据。在室内恒温培养条件下（25℃）,研究了正丁基硫代磷酰三胺（NBPT）、醋酸棉酚、硫代硫酸铵3种脲酶抑制剂对石灰性土壤各形态氮素转化与脲酶抑制率的影响,同时在人工气候室（昼夜）通过Unisense N2O微电极法对各处理土壤N2O浓度进行了原位实时监测。结果表明：尿素施入土壤1 d后50%已迅速水解,3d后完全水解。1～14d各脲酶抑制剂均可显著抑制尿素水解,尿素＋NBPT处理的土壤尿素残留量显著高于其他处理,其脲酶抑制率为33.6%;NBPT处理的土壤NH4^＋-N含量低于其他各处理（P〈0.05）,在第7d分别比尿素、尿素＋硫代硫酸铵、尿素＋醋酸棉酚处理的降低了64.8%、63.5%、70.9%。土壤N2O浓度在第1～4 d较低,第4d后迅速上升,第6 d升至峰值,随后呈明显下降趋势（第6～9 d）。第9～14d各处理N2O的排放表现为尿素〉尿素＋醋酸棉酚〉尿素＋硫代硫酸铵≥尿素＋NBPT。各形态氮与N2O浓度的通径系数分别为NO3^--N（0.641）〉NH4^＋-N（0.356）〉Urea-N（0.255）,通径相关和线性相关均表明NO3^--N含量与N2O浓度呈显著正相关,是制约N2O排放的主导因素。石灰性土壤施用脲酶抑制剂可抑制土壤尿素水解转化,有效降低土壤N2O浓度,3种脲酶抑制剂中NBPT效果最佳。

Understanding the effects of urease inhibitors on urea hydrolysis and soil nitrous oxide（N2O）emissions may help improve fertilizer N utilization efficiency and mitigate soil N2O production in calcareous soil. In the present research, the effects of three different urease inhibitors, N-（N-butyl）thiophosphoric triamide（NBPT）, ammonium thoisulfate（ATS）and gossypol acetate（GA）, on urea hydrolysis dynamics and soil ammonium and nitrate transformations were examined in a soil culture experiment under greenhouse conditions. Soil N2O concentrations were also determined in situ using Unisense N2O micro-sensor. Fifty percent of applied urea was hydrolyzed within one day, and almost all applied urea hydrolyzed within three days after amendment. During 14 day period, urea hydrolysis was obviously inhibited by NBPT, ATS and GA. In the NBPT amendment, the inhibition rate was greatest, with 33.6%, and urea residue in soil was the highest. Soil NH4^＋-N content was statistically lower in NBPT supply than in other treatments（P〈0.05）. Soil N2O concentrations maintained very low during of the first 4 day, then increased sharply,until the peak occurring on the 6th day, and then decreased obviously during 6^th～9^th day. Soil N2O concentrations were in order：urea〉urea＋GA〉urea＋ATS≥urea＋NBPT. Furthermore, N2O concentrations were higher during the day than at night, with diurnal variation ranging from 0.25～3.15 μmol·L^-1. The path coefficients between N2O concentration and different forms of soil mineral N were：NO3^--N（0.641）NH4^＋ -N（0.356）Urea-N（0.255）. There was a significant positive relationship between soil NO3^--N and N2O contents, indicating that soil nitrate would be one of key factors influencing soil N2O emission. In conclusion, applying NBPT, ATS and GA inhibits urea hydrolysis and decreases soil N2O generation in calcareous soil, with NBPT as a promising urease inhibitor.