| Project/Area Number |
06453163
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Plant nutrition/Soil science
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| Research Institution | Kyushu University |
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Principal Investigator |
WADA Shinichiro Kyushu University, Faculty of Engineering, Associate Professor, 農学部, 助教授 (60108678)
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| Co-Investigator(Kenkyū-buntansha) |
ITOI Ryuichi Kyushu University, Faculty of Agriculture, Associate Professor, 工学部, 助教授 (50108768)
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥7,300,000 (Direct Cost: ¥7,300,000)
Fiscal Year 1995: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1994: ¥6,000,000 (Direct Cost: ¥6,000,000)
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| Keywords | pH / Soil / Soil solution / ion exchange / cation adsorption / Anion adsorption |
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| Research Abstract |
Although soil chemical and biological properties have been described as a function of soil pH in many soil science studies, soil pH is one of the independent variables which should be predicted from the amounts of materials input to, output from and produced in soil.
In the first of this project, we conducted basic experimental studies on the stoichiometry of cation and anion adsorption on variable charge materials and soils, which is crucial in predicting hydrogen ion activity in soil solution, i.e., soil pH.The 1 : 1 relationship between Ca and Mg adsorption (in mol/kg) on allophanic and humic Andisols and pH-1/2pM revealed that these divalent ions occupy two surface functional groups. The constancy of Na plus Ca adsorption (in mol (+) /kg) on a noncrystalline silica during Ca-Na exchange processes directly showed that Ca occupies two dissociated silanol groups on silica surfaces. Sulfate adsopriton from sodium sulfate and calcium sulfate solutions on a allophanic Andisol was uniquely determined by the pH+1/2pSO4, suggesting that sulfate adsorbs on allophane occupying two protonated surface hydroxyl groups. We also measured carbonate adsorption by allophanic soil and found that the effect of carbon dioxide concentration on it is relatively small.
In the second part, we developed a basic numerical model incorporating cation and anion adsorption by soils and simulated the change in soil solution pH during the dilution of soil solution. The deviation of the predicted pH values increased at higher dilution ratios, but the difference was with in 0.3 pH unit.
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