我国土壤中的固定态铵

叙述了全国除高山土带和亚高山土带外各土带土壤中固定态铵的绝对含量和相对含量以及各主要土壤的固铵能力，讨论了固定态铵的来源、影响固定态铵含量和土壤固铵能力的因素。以及铵的固定和释放在土壤氮素内循环中的意义。以土带为单位，各土带中，黄棕壤带内的土壤的固定态铵含量较高，为２５７ｍｇ／ｋｇ，砖红壤带内的土壤最低，仅为４８ｍｇ／ｋｇ。耕地土壤０～２０ｃｍ土体中，固定态铵的储量全国平均约为全氮储量的１５％。各

FIXED AMMONIUM IN SOILS OF CHINA

In this paper both the absolute and relative contents of fixed NH4+ in soils of soil zones except the alpine and subalpine soil zones of China are presented, the NH4+ fixation capacity and the availability of fixed NH4+ of najor soil groups are indicated. The origin of fixed NH4+, the factors affecting the content of fixed NH4+ and the ability for fixing NH4+ of soil, and the significance of NH4+ fixation and defixation in the internal cycle of soil N are disccussed. The content of fixed NH4+ in soils of yellow brown soil zone, as a whole, is the highest, being 257 mg/kg, while that of latosol zone is the lowest, being 48 mg/kg. On average about 15% of N to depth of 20cm for the cultivated soils as a whole of China was estimated to occur as fixed NH4+. Of the native fixed NH4+, dependent on both the kind of parent material (rock) and the degree of weathering of the soil, from 3% to 20% can be utilized by plant.The NH4+ fixation capacity of soils of yellow brown soil zone is also the highest, while soils of latosol zone, lateritic red soil zone, grey brown desert soil zone and brown desert zone as well as some soils in the red soil zone are unable to fix added NH4+. Based on the differences in the amount of fixed NH4+ and its contribution to soil N pool, as well as in the ability for fixing NH4+, soils in China except those in the alpine and subalpine soil zones are grouped into 10 soil regions.