Evaluation of availability of phosphorus reserved in Andisols for high yield of crop and savings of phosphorus resources.

以土壤胶体组成为参照，评价了红壤的磷素肥力。磷吸附量与活性铝（铝英石和铝-腐殖酸复合体）密切相关。以铝-腐殖酸络合物的活性铝为主的非脲基型安地土比以脲基烷的活性铝为主的脲基型安地土表现出更高的磷吸附容量。土壤有效磷含量随土壤磷吸附量的增加而降低，用EDTA-NaF溶液提取土壤中可溶性无机磷总量。植物吸收更大量的磷从脲基化的Andisol比nonallophanic Andisol具有相同水平的总可溶性P和有效P（Truog和Bray方法）。与脲醛树脂型土壤相比，非脲醛树脂型土壤需要更多的有效磷才能促进植物生长。脲基甲酸安地索的Truog-P和阴离子交换树脂可提取P值高于非脲基甲酸安地索，而可溶性P总量相同。非脲基化合物Andisol表现出较高的Bray值，结果表明，在土壤胶体P含量相同的情况下，有机磷和乙酸提取态P的含量要高于脲基甲酸型土壤，因此，准确评价土壤P的有效性，必须考虑土壤胶体P含量的影响，采用提取法在pH低于5.3的非脲基化土壤中，植物有效磷含量降低，而土壤有效磷含量在pH 4.5~7.0范围内变化不大。在低pH条件下，铝伤害抑制了根的伸长，导致植物对磷的吸收减少。

Phosphorus (P) fertility of Andisols was evaluated with reference to colloidal composition of soils. P sorption capacity was strongly correlated to active aluminum (allophane and Al-humus complex). Nonallophanic Andisols with major active aluminum of Al-humus complex showed a higher P sorption capacity per active aluminum than allophanic Andisols with major active aluminum of allophane. Soil available P content decreased with increasing of P sorption capacity of soil.Total soluble inorganic P reserved in soil was extracted by EDTA-NaF solution. Plant absorbed greater amounts of P from allophanic Andisol than nonallophanic Andisol with equal level of total soluble P and available P (Truog and Bray methods). Nonallophanic Andisol needed more available P for good plant growth with compared to allophanic Andisol. Allophanic Andisol showed higher value of Truog-P and anion exchange resin extractable P than nonallophanic Andisol with equal amount of total soluble P.However, nonallophanic Andisol showed higher value of Bray-P and acetic acid extractable P than allophanic Andisol with equal amount of total soluble P.It was concluded that the accurate evaluation of P availability of Andisols must be conducted by extraction methods in consideration for soil colloidal composition.Plant available P decreased in nonallophanic Andisol with low pH less than 5.3.Soil available P contents did not change within the pH range of 4.5 to 7.0. In low pH,the inhibition of root elongation by Al injury caused the reduction in P absorption of plant.