湖南主要类型稻田土壤固定态铵含量及其影响因素

通过野外调查取样和室内培养试验 ,应用Silva和Bremner方法 ,研究了湖南省主要类型稻田土壤的固定态铵含量及其影响因素 .结果表明 ,该省主要类型稻田土壤固定态铵含量为 141～ 35 3mg·kg-1,平均为 2 72± 6 7mg·kg-1,占土壤全N的 11.2 % ,高于湖南省以北各地区土壤和本地区地带性土壤———红壤的固定态铵含量 .其含量的顺序为河沙泥 >紫泥田 >潮沙泥 >黄泥田 >红黄泥 .在土壤剖面中 ,固定态铵含量随剖面深度的变化有 4种情况 :在 1m深度范围内随深度增加而增加 ;随深度增加而减少 ;随深度增加而无明显变化 ;土壤剖面中某一土层固定态铵含量明显增加或减少 .土壤固定态铵含量占土壤全N百分比随深度增加而恒增大 .土壤对NH+ 4的固定作用在 30℃下最强 ,高于 2 0℃和 40℃ ;长期淹水有利于潮沙泥、紫泥田和河沙泥对NH+ 4的固定作用 ,但干湿交替有利于黄泥田对NH+ 4的固定作用 .相关分析表明 ,土壤固定态铵含量仅与 <0 .0 1mm粘粒含量呈P0 .0 5水平的显著正相关 ,与有机质、全N、有机N和 <0 .0 0 1mm粘粒含量的相关性均不显著

Fixed ammonium content of chief paddy soil types in Hunan Province and its influencing factors

By the method of Silva and Bremner, the fixed ammonium content of chief paddy soil types in Hunan Province and its influencing factors were studied. The results showed that the content of fixed ammonium in plough layer ranged from 141 mg.kg-1 to 353 mg.kg-1, averaged 272 +/- 67 mg.kg-1, and accounted for 11.2% of total soil N. The content of fixed ammonium was in order of alluvial sandy soil > purple clayey soil > newly alluvial sandy soil > yellow clayey soil > reddish yellow clayey soil. There were four distribution models of fixed ammonium in the soil profiles: 1) fixed ammonium content increased with the increase of depth in the profiles; 2) fixed ammonium content decreased with the increase of depth; 3) there was no distinct change; and 4) abrupt increase or decrease was found in the profiles. The percentage of fixed ammonium to total N in soils always increased with the increase of depth. The fixation of NH4+ by soil was the strongest under 30 degrees C. Long-term submergence benefited to the fixation of NH4+ in newly alluvial sandy soil, purple clayey soil, and alluvial sandy soil, while the alternation of drying and wetting contributed to the fixation of NH4+ in yellow clayey soil best. The content of fixed ammonium in tested soil was correlated with the content of clay < 0.01 mm at the significant level, and not correlated with the content of clay < 0.001 mm, total N, organic N, and matter.