杭嘉湖平原水稻土磷的固定和释放特性研究

Characteristics of phosphorus fixation and release in paddy soils of the Hangzhou-Jiaxing-Huzhou Plain

选择代表性土壤8个，采用等温吸附和室内加磷培养及化学提取等试验。研究了杭嘉湖平原主要水稻土对磷的固定和释放特性。结果表明：杭嘉湖平原水稻土对磷的吸附能力属中等水平，淹水还原条件下土壤对磷的吸附量明显高于氧化条件下的吸附量。前者在567．0～1505．0mg／kg之间。后者在415．2～809．2mg／kg之间，前者为后者的1．32～2．28倍。该区土壤对磷的吸附量主要与粘粒含量有关。加磷培养试验表明：水溶性磷随培养时间的增加而下降，至7d达到动力学平衡。水溶性磷含量随土壤磷的积累呈指数增加。但随提取次数的增加而降低。在磷吸附作用较强的土壤中，水溶性磷随磷积累增加的变化程度小于磷吸附作用较弱的土壤。结果表明。用土壤磷的饱和度可很好地表征土壤磷的释放特性与磷积累的关系。

Eight representative paddy soils from the Hangzhou-Jiaxing-Huzhou Plain were used as test materials, and tests for soil P were carried out through isothermal adsorption, indoor incubation of soil treated with P, and chemical extraction of soil P in order to study the effects of P accumulation on P leaching loss and migration in the soils. The results showed that P adsorption capacity of the soils was medium, and the maximum P adsorption capacity of the soils, calculated by Langmuir model, ranged from 415.2 to 809.2 mg/kg in the oxidizing condition, and from 567.0 to 1 505.0 mg/kg in the reducing condition. The maximum P adsorption capacity of the soils in the reducing condition was 1.32-2.28 times of that in the oxidizing condition. The adsorption capacity was mainly related to soil clay content. The indoor incubation experiment indicated that water-soluble P in the soils decreased until it reached dynamic equilibrium on the 7th day of incubation. The water-soluble P presented exponential growth with P accumulation in the soils, and declined with increasing of the times of successive extraction. The water-soluble P growth with P accumulation in the soil of high P adsorption capacity changed less than that in soil of low P adsorption capacity. Degree of P saturation could be well characterized the relationship between release behavior and accumulation of P in the soils.