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用豇豆(Vigna unguiculata)、田菁(Sesbania aculeata)和柽麻(Crotolaria,juncea)改良碱性砂壤土(Udic Ustochrept)的磷吸附特性,经过20天和40天培育后测定。被吸附的磷量因绿肥的加入和淹水期的延长而减少(豇豆>田菁>柽麻),(以0.2μgP/ml作为嫌气土壤溶液中磷的临界值)。绿肥的嫌气分解降低了结合能及磷最大吸附量,可能是植物残体矿质化过程中释放磷之故。另外,分解过程中积累的有机酸与金属阳离子络合,促使土壤中原有的磷溶解,减少了施入的无机态磷的固定。这样,嫌气土壤施用绿肥明显地降低了磷的吸附能力,在土壤磷的管理措施中应该考虑这一点。磷吸附等温线可用于预测最佳产量时的磷素水平,也可用于测定绿肥取代的无机磷肥的用量。
Phosphate adsorption characteristics of Udic Ustochrept with Vigna unguiculata, Sesbania aculeata and Crotolaria juncea were determined after incubation for 20 days and 40 days. The amount of phosphate absorbed decreased with the addition of green manure and the prolongation of flooding period (cowpea> Sesbania> Abutilon theorum), (0.2μgP / ml was used as the critical value for phosphorus in anaerobic soil solution). Anaerobic decomposition of green manure reduces the maximum binding capacity and phosphorus adsorption, which may be due to the release of phosphorus during mineralization of plant residues. In addition, the organic acid accumulated during decomposition is complexed with metal cations to promote the dissolution of the original phosphorus in the soil and reduce the immobilization of the inorganic phosphorus applied. Thus, application of green manure to anaerobic soil significantly reduces phosphorus adsorption capacity, which should be taken into account in soil phosphorus management practices. Phosphorus adsorption isotherms can be used to predict the optimum production of phosphorus levels can also be used to determine the amount of green manure replaced inorganic phosphate fertilizer.