Characteristics in Phosphate Adsorption of Major Soil Groups of Thailand

JARQ : Japan Agricultural Research Quarterly
ISSN 00213551
書誌レコードID(総合目録DB) AA0068709X

 Phosphate adsorption in the major soil groups in Thailand was examined over the wide range of pH and equilibrium P concentration, and the characteristics of these soils in P adsorption were discussed in terms of Langmuir adsorption model and equilibrium diagrams for phosphate compounds.
 P adsorption increased steeply at pH values where buffer intensity of the soils was at its maximum. Thus, P adsorption is greatly affected by kinds and amounts of soil components responsible for H+ or OH- acceptance.
 P adsorption by Grumusol increased steeply due to precipitation of calcium phosphate compounds above pH 6 when more than 75 ppm of phosphate was added. The product of actual ion concentration, QST= (CaT)x×(PT)y, also exceeded conditional solubility product, Ps= c*Kso(H+)z/(αca)xH2PO4)y around 6, and adsorption isotherm indicated that phosphate was precipitated as calcium phosphates.
 P adsorption by ASS reached its maximum around pH 5, but adsorption isotherm at this pH value showed that the precipitation of alumino-phospho compounds in the bulk solution was not significant even at 150 ppm, therefore, this is due to the formation of surface chelating compounds with hydroxy-aluminium. Rock phosphate with high content of Ca is highly recommendable as a phosphate fertilizer to ASS. P adsorption in FWA increased greatly in acidic pH region when high concentration of P was added and then decreased smoothly with increasing the equilibrium pH. This reflects structural fragility of the soil, and indicates that clay with ill-defined structure and amorphous materials are responsible for P adsorption in this soil.
 P adsorption in RBL and NCB is much less than in Grumusol and ASS. Fe contained in RBL seems to be inactive unless P concentration is high and pH is very low. So that there is no need to pay much attention in ordinary levels of phosphate fertilization.

国立情報学研究所メタデータ主題語彙集(資源タイプ) Journal Article
開始ページ 59
終了ページ 68
言語 eng