| Summary: | 碩士 === 國立中興大學 === 土壤學研究所 === 82 === Strongly acid soils have been known to have strong phosphorus(P) sorption capacity, however, the capacities may be affected by the characteristics of soils and the addition of lime or P fertilizer. It will be more complicate of P transformation and P availability in the soils when organic matter, lime, and chemical P fertilizer are used in strongly acid soils, and needed to investigate. The objectives of this research were to study (1) the effect of lime and chemical P fertilizer addition on the sorption capacity of inorganic and organic P of strongly acid soils, and to evaluate the suitability of four P sorption isotherms in describing P sorption characteristics of soils after lime and chemical P fertilizer were added; (2) the effect of the interacactions of lime-organic matter-chemical P fertilizer on the P availabilities of strongly acid soils.
Three different soils (kuan-Si, Chun-Liao, and Bei-Go) with various weathering degree and P sorption capacity were selected in this study. Soils were limed to three different pH levels with Ca(OH)2, and two rates of KH2PO4 were added, then were incubated at room temperature (25). The changes of organic and inorganic P sorption capacity of the soils were determined after twenty days. Additionally, four P sorption isotherms (Linear Langmuir isotherm. Modified Langmuir istherm, NonLinear Langmuir isotherm, and freundlich equation) were evaluated their suitabilities in describing P sorption characteristics after lime and chemical P fertilizer were added. Moreover, Kuan-Si and Chun-Liao soils were selected to stuty the combined effects of lime, organic matter, and chemical P fertilizer on the availability and transformation of P in the soils.
Results showed that the organic P and inorganic Psorption capacities of strongly acid soils were increased with the degree of soil wearthering. The effect of lime addition on the sorption capacity for inorganic and organic P of strongly acid soils varied with the pH and. P sorption capacity of soils. In addition, the contents of Al saturation, amorphous Al and clay were the main factors in controlling the organic P sorption capacity of strongly acid soils. Generally speaking, chemical P fertilizer addition was found to decrease the organic P sorption capacity of soils. Linear Langmuir isotherm was more suitable than other isotherms in describing P sorption characteristics of soils after lime and chemical P fertilizer were added.
The concerntration of solution P and resin exchangeable P were increased by the used of chemical P fertilizer and organic fertilizers. However, the effect of liming depends on the contents of exchangeable Al or Al saturation of soils. Results also indicated that the combined addition of lime, organic matter, and chemical P fertilizer was the best practice of management in promoting the P availability of strongly acid soils in Taiwan.
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