稻田土壤中硝化速率的测定

Estimation of Nitrification Rates of Paddy Soils

采用３种测定硝化速率的技术，对３种土壤短期培养进行了测定，这３种技术分别为铵氧化抑制法、硝酸氧化抑制法和同位素稀释法。硝酸氧化抑制法测定的硝化速率偏低，在供试的４种硝化抑制剂中，氰化钾、ＡＭＴ和ＤＭＵ均属于非专性，氯酸钾基本不显效果。在４种铵氧化抑制剂中，２ＥＰ和ＰＡ的酒精溶液会促进铵的固定，乙炔和２ＥＰ的乳状、液抑制铵氧化的效果相似，对氮的矿化与固定速率影响不大，ＡＴＵ基本无效。两种同位素稀释性测定的硝化速率基本相同，其测定结果与铵氧化抑制法的测定结果在供试的一种土壤上相吻合，但在另两种土壤上前者测定结果偏低，这可能是由于硝酸还原产生的铵硝化后导致对硝化速率的低估。

Three techniques for estimating nitrification rates in flooded soils were evaluated in Short-term incubation experiments using three soils. The techniques were based on inhibition of eitherammonium or nitrite oxidation and ￣(15)N isotope dilution. Nitrification rates were underestimated bythe method based on inhibition of nitrite oxidation. Of four inhibitors evaluated , potassium cyanide, 2-ethlamino4- isopropylamino - 6 - methylthio - s - triazine (ametryne ) and 3 - ( 3, 4 -dichlorophenyl)- 1- methylurea (DMU ) were non -spoific, and potassium chlorate was notcompletely effeetive. Of four inhibitors of ammonium oxidation evaluated, one (allylthiourea) wasineffective and two (2- ethynylpyridine or phenyl acetylene dissolved in ethanol) promotedimmobilization of ammonium. Emulsified 2 - ethynylpyrdine and acetylene were equally effectiveinhibitors of ammonium oxidation,and had little or no effect on gross rates of N mineralization andimmobilization. Similar estimates of nitrification rates were obtained by two models based on isotopedilution. These rates were similar to rates estimated by inhibition of ammonium oxidetion in one soil ,but were lower in the other two soils. Nitrification of labelled ammonium derived from dissimilatorynitrate raduction resulted in underestimation of nitrification rates by isotope dilution.