土壤有效磷是指耕层土壤中能供作物吸收的磷元素的含量。以每千克干土中所含P的毫克数表示,包括全部水溶性磷、部分吸附态磷及有机态磷,有的土壤中还包括某些沉淀态磷。在化学上,有效磷定义为:能与32P进行同位素交换的或容易被某些化学试剂提取的磷及土壤溶液中的磷酸盐。作物吸收磷的形态,包括无机磷和有机磷两大类。在 Soil available phosphorus refers to the amount of phosphorus that can be absorbed by plants in the topsoil. Expressed in milligrams of P per kilogram of dry soil, including all water-soluble phosphorus, partially adsorbed phosphorus, and organic phosphorus, some of which also include some precipitated phosphorus. Chemically, available phosphorus is defined as phosphate in soil that can be isotopically exchanged with 32P or readily extracted with certain chemicals. Crops absorb phosphorus forms, including inorganic phosphorus and organic phosphorus two categories. in