湖南稻田土壤固定态铵含量的季节变化及生物有效性

以湖南省3种固定态铵含量较高的稻田土壤为供试土壤，通过盆栽试验，研究了稻田土壤固定态铵在植稻期间的动态变化及其生物有效性。结果表明，稻田土壤的固定态铵含量处于不断的变化之中，施氮肥和有机肥使土壤固定态铵含量升高，而水稻吸收氮则使土壤固定态铵含量降低，其变化趋势与土壤碱解氮含量变化相似。“新固定的”固定态铵基本对当季水稻全部有效。而“原有的”固定态铵对当季作物和后季作物部分有效，就供试土壤而言，在水稻生育期间，土壤固定态铵的释放量是潮沙泥>紫泥田>河沙泥；就不同水稻而言，早稻生育期间土壤固定态铵的释放量大于晚稻生育期间土壤固定态铵的释放量。

Seasonal variation of fixed ammonium content of paddy soils in Hunan Province and its bioavailability

Three paddy soils with higher content of fixed ammonium in Hunan Province were used as test soils in pot experiment to study the seasonal variation of their fixed ammonium content and its bioavailability during rice growth period. The results showed that the fixed ammonium content in the paddy soils changed constantly during rice growth. Applying N fertilizer and organic manure increased the fixed ammonium content, which was decreased through the N uptake by rice plants. The recently fixed ammonium was almost fully available to rice, while the native fixed ammonium was partly available. The release of fixed ammonium during rice growth was newly alluvial sandy soil > purple clayey soil> alluvial sandy soil, and was greater at early growth stage than at later growth stage.