岩溶农业区典型土地利用土壤磷素空间分布与成因

为了查明岩溶农业区不同土地利用下磷素在垂直和平面上的分布情况,分析岩溶农业区土壤中磷素的迁移特征及其影响因素,采集了凯掌水库周边草地、河滨带、水田及旱地等典型土地利用下的9个土壤剖面共计56个样品,分别测定各个土壤剖面的含水率、pH、有机质、交换性酸、全磷、有效磷、各无机磷形态等。结果表明：研究区全磷、有效磷含量分别在420.73~1669.53 mg/kg和2.50~64.14 mg/kg之间,土壤磷活化系数在0.34%~5.96%之间。农业用地表层土壤有效磷含量均超过15 mg/kg,需减少磷肥的施用以避免浪费,同时坝后农业区旱地表层土壤（有效磷平均含量64.14 mg/kg）中的磷存在向下淋溶进入地下水的风险。水田、旱地剖面土壤无机磷形态以Fe-P、Al-P为主,草地、河滨带剖面无机磷形态以Fe-P和O-P为主。土壤pH与有效磷、Fe-P和Al-P呈显著负相关,土壤有机质与全磷、有效磷、Al-P、Fe-P显著正相关。本研究阐明了岩溶农业区磷素及其形态的空间分布规律,可为磷的农业面源污染防控提供依据。研究区农业用地土壤磷素含量普遍高于非农业用地,不同土地利用类型对磷素分布具有显著影响。

Spatial Distribution and Formation of Phosphorus in Typical Land-use Soils in Karst Agricultural Areas

A study on the spatial distribution, migration characteristics and influencing factors of phosphorus in vertical and horizontal soil under different land use types in karst agricultural areas was carried out. A total of 56 samples were collected from 9 soil profiles under typical land use types (grassland, riverside, paddy field, dry land, etc.) around Kaizhang reservoir, and the water content, pH, organic matter, exchangeable acid, total phosphorus, available phosphorus and inorganic phosphorus of each soil profile were determined. The results demonstrated that the total phosphorus content and available phosphorus content were measured to be over a wide range of 420.73-1669.53 mg/kg and 2.50-64.14 mg/kg, respectively, and the soil phosphorus activation coefficient was in the range of 0.34%-5.96%. It was found that available phosphorus content in the surface soil of agricultural land was more than 15 mg/kg, which was correlated with the overuse and waste of phosphate fertilizer. Meanwhile, the risk of phosphorus leaching downward into underground water was found in the surface soil of dry land in the agricultural area behind the dam (the average content of available phosphorus was 64.14 mg/kg). The soil inorganic phosphorus forms in paddy field and dry land were mainly Fe-P and Al-P, and in grassland and riverside were mainly Fe-P and O-P. The results indicated that soil pH was significantly and negatively correlated with available phosphorus, Fe-P and Al-P, and soil organic matter was significantly and positively correlated with total phosphorus, available phosphorus, Al-P, and Fe-P. It is concluded that the soil phosphorus content of agricultural area is generally higher than that of non-agricultural area because of different phosphorous distributions in different land use types. The study clarifies the spatial distribution of phosphorus and its forms in karst agricultural areas, which could provide a basis for the prevention and control of agricultural non-point source pollution caused by phosphorus.