摘要:中国南方黄泥田土壤中养分淋失严重，尤其是氮（N）和钾（K），不仅造成资源浪费和潜在环境威胁，还严重制约作物的可持续生产。采用室内土柱模拟培养，研究尿素（U）和尿素硝铵（UAN）中单独添加脲酶抑制剂N-丁基硫代磷酰三胺（NBPT）和硝化抑制剂2-氯-6-（三氯甲基）吡啶（CP），及两者配合施用对黄泥田土壤中K素淋溶特征的影响，探讨提高黄泥田供钾能力的施肥技术。不同氮肥种类淋溶液中，K+平均浓度大小表现为UAN处理（103.0 mg·kg-1）高于U处理（93.9 mg·kg-1），且抑制剂处理间存在明显差异。培养结束时（第72 d），UAN处理K+淋失量较U处理高6.7%。U各处理淋溶液中K+累积量大小表现为U > U+NBPT > U+NBPT+CP > U+CP > CK，其中U+NBPT、U+CP和U+NBPT+CP处理较U处理分别降低8.7%、20.2%和14.9%；UAN各处理淋溶液中K+累积量表现为UAN > UAN+NBPT > UAN+NBPT+CP > UAN+CP > CK，其中UAN+NBPT、UAN+CP和UAN+NBPT+CP处理较UAN处理分别降低6.0%、13.8%和9.2%。不同施肥处理K+淋溶率表现为UAN > UAN+NBPT > U > UAN+NBPT+CP > UAN+CP > U+NBPT > U+NBPT+CP > U+CP。培养中期（第36 d），U和UAN处理肥际微域中土壤速效钾含量显著降低，而添加CP处理有效维持土壤中较高的速效钾含量。与单施NBPT相比，配施CP可以减少黄泥田土壤中NO3-淋溶，增加土壤晶格对K+的固定，减轻K+淋溶风险，有效时间超过72 d。对各处理淋溶液中K+累积量（y）随NO3-累积量（x）的变化进行拟合，其中以线性方程（y=ax+b）和Elovich方程（y=alnx+b）的拟合度最高，且抑制剂处理间a、b值均存在明显差异。总之，在黄泥田土壤中单施CP，或与NBPT配施可以有效增加K+吸附，降低土壤中K+淋溶损失，减轻养分淋失风险，提高肥料利用率。
关键词:钾淋溶/
黄泥田土壤/
脲酶抑制剂/
硝化抑制剂/
尿素/
尿素硝铵
Abstract:Soil nutrient leaching in yellow clay soils, especially nitrogen (N) and potassium (K) leaching, is extremely serious in South China. This has resulted in not only waste of resources and potential environmental threat, but also in serious restriction on sustainable production of crops. In this study, the effects of urease inhibitor[N-(n-butyl) thiophosphoric triamide, NBPT], nitrification inhibitor[2-chloro-6-(trichloromethyl) pyridine, CP] and their combined application on leaching characteristics of K in yellow clay soils were investigated in an indoor soil column simulation with urea (U) and urea ammonium nitrate (UAN) application. The study aimed to improve the capability of soil K through rational application of biochemical inhibitors. In the leaching solution of different N fertilizers, higher average K+ concentration was obtained under UAN treatments (average in 103.0 mg·kg-1) than under U treatments (average in 93.9 mg·kg-1), with obvious differences among inhibitor treatments. At the end of incubation (72 days after incubation), UAN treatments increased K+ leaching average by 6.7% more than U treatments. K+ accumulation in leaching solution under U treatments was in the order of U > U+NBPT > U+NBPT+CP > U+CP > CK. Compared with U treatment, U+NBPT, U+CP and U+NBPT+CP treatments reduced K+ accumulation by 8.7%, 20.2% and 14.9%, respectively. K+ accumulation under UAN treatments was in the order of UAN > UAN+NBPT > UAN+NBPT+CP > UAN+CP > CK. Compared with UAN treatment, K+ accumulation in UAN+NBPT, UAN+CP and UAN+NBPT+CP treatments were reduced respectively by 6.0%, 13.8% and 9.2%. Additionally, leaching rate of K+ across different treatments was in the order of UAN > UAN+NBPT > U > UAN+NBPT+CP > UAN+CP > U+NBPT > U+NBPT+CP > U+CP. In the middle of incubation (36 days after incubation), soil available K content of fertilizer microsites under U and UAN treatments decreased significantly. The addition of CP effectively maintained high availability of K content in the topsoil. Compared with the addition of NBPT alone, combined application of NBPT and CP reduced NO3- leaching, increased K+ fixation on soil lattice and mitigated leaching risk of K+ for more than 72 days in yellow clay soils. Equation models were used to describe the relationship between K+ accumulation (y) and NO3- accumulation (x) in leaching solution. The linear equation (y=ax+b) and Elovich equation (y=alnx+b) fitted well, with a and b values for inhibitor treatments obviously different. In conclusion, the application of CP alone or in combination with NBPT in yellow clay soils effectively increased the adsorption of K+, minimized soil K+ leaching loss, mitigated the risk of nutrient leaching and improved fertilizer utilization rate.
Key words:Potassium leaching/
Yellow clay soil/
Urease inhibitor/
Nitrification inhibitor/
Urea/
Urea ammonium nitrate
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