不同利用方式下农田土壤对磷的吸持与解吸特征

不同利用方式下农田土壤水土界面磷的迁移能力有较大的差别.模拟实验结果表明,太湖地区水稻土在旱作时土壤固磷能力低于旱地土壤,但由于其土壤磷素水平较后者低,在一定条件下磷由固相转入液相被淋溶或随径流流失的风险要低于旱地土壤.水稻土在淹水还原条件下比旱作时固磷能力有了较大幅度的提高,土壤中的磷向溶液中的释放量总体上较淹水前减少,这是因为在还原条件下形成的无定形Fe³⁺-Fe²⁺混合氢氧化物具有巨大的表面积和很强的吸持能力,增强了对磷的固定.

Phosphorus Sorption and Desorption of Agricultural Soils under Different Land Uses

The potential of P loss from soils under different land uses in Taihu Lake watershed was evaluated by laboratory experiment. It was shown that although the P sorption capacity of paddy soils under oxidized conditions were little lower than that of dryland soils the risks of P loss from the former via runoff and leaching were lower than that from the latter, because the soil P levels of the former were much lower than that of the latter. For most paddy soils the P sorption capacity increased and the P release decreased under reduced conditions than that under oxidized conditions and this was attributed to the formation of amorphous Fe²⁺ hydroxides which have a greater surface area and more P sorption sites than well crystallized Fe³⁺ oxides.