Call Prefix : PR-T

Call Suffix : 1992

Call Cutter : D - SoSc 19

Location : SEARCA Library

Format : TD

Publisher : University of the Philippines Los Banos,

Publication Date : October 1992

Publication Place : Laguna, Philippines :

Summary : Two Red Yellow Podzolic soils and one Andosol from Lampung in Southern Sumatra were studied in a laboratory and greenhouse to determine some chemical and mineralogical properties and the influence of some soil management practices on soil phosphorus (P) in terns of extractable P and selected inorganic P fractions as well as P uptake and dry matter yield of soybean. The soils differed in their acidity (pH and total exchangeable acidity), mineralogical properties, total P content, extractable P, P sorption capacity, and their P fractions (A1-P, Fe-P, and Ca-P). The laboratory study showed that addition of lime, as rock phosphate, and rice straw increased pH and extractable P of the three soils. The three soils differed in their response to addition of lime, rock phosphate, and rice straw with regards to their pH, extractable P, A1-P, Fe-P, and Ca-P. The effect of treatments also differed depending on whether the samples were leached or unleached during incubation and depending on the time the samples were collected during incubation. The extractable P in leached samples was lower than in unleached samples. Addition of silicated lime to the Podzolic soils resulted in higher extractable P. However, in the Andosol, the two sources did not differ in extractable P. The effect of treatments on A1-P, Fe-P, and Ca-P fluctuated with time of sampling but A1-P and Fe-P tended to decrease and Ca-P tended to increase although the soils differed in the sampling period when the increase or decrease occurred and depended on whether the sample was leached or unleached. The greenhouse study showed that dry matter yield and P uptake of soybean were much higher in Andosol than in Podzolic soil. The effects of lime, rock phosphate, and rice straw were significant for dry matter yield and P uptake of soybean. However, the effect of the three treatments interacted with each other in the Podzolic soil. For Andosol, the interactions were only: lime x rock phosphate, lime x rice straw, and rock phosphate x rice straw. Lime added increased the pH in both the Podzolic and Andosol but beyond the expected pH and the results were consistent with those from laboratory experiment. Addition of rock phosphate in Podzolic soil increased extractable P but rice straw tended to decrease the value slightly when recommended lime rate was applied. In the Andosol, the extractable P at harvest increased from its initial level. The increase appeared associated with rice straw addition particularly in samples that received lime. Al-P in Podzolic soil decreased in pots applied with the silicate lime but increased with carbonate lime. In Andosol, Al-P differed only slightly among the treated samples. Fe-P decreased sharply at harvest in Podzolic soil but increased in Andosol. Ca-P increased in Podzolic soil due to addition of rock phosphate but the increase was greater in Andosol due to addition of rice straw.