湖南省某些稻田土壤固定态铵的剖面分布

利用Silva-Bremner法测定了湖南省某些稻田土壤各剖面的固定态铵量，揭示了其分布规律。固定态铵绝对含量的剖面分布规律有4种类型：第1类为土壤固定态铵随剖面深度增加而增大；第2类是土壤固定态铵随剖面深度增加而减小；第3类是土壤固定态铵随剖面深度变化不明显；第4类是土壤固定态铵在土壤剖面某一土层中明显增大或减少，特别明显的是犁底层的固定态铵量常比耕作层要高。这与成土过程、母质类型以及人为活动等因素有关。固定态铵相对含量分布常从上至下逐渐增加。

Profile distribution of fixed ammonium in some paddy soils in Hunan province

Using the method suggested by Silva-Bremner (1966) the absolute content of fixed ammonium in the profiles of paddy soils derived from some major parent materials in Hunan province was studied. There are four distribution models of fixed ammonium in the profiles: firstly, the content of fixed ammonium increases with increasing depth in the profiles; secondly, it decreases with increasing depth; thirdly, there is no sharp change in the profiles; fourthly, abrupt increase or decrease is found in the profiles, and it is often observed that the content of fixed ammonium in the plowpan layer is more than that in the plough layer. The regularity is related to soil process, parent materials and human activities and so on. The relative content of fixed ammonium usually increases with increasing depth in the profiles.