The dissolution of calcium silicate slag fertilizers in flooded soil
1996
Kato, N. (National Inst. of Agro-Environmental Sciences, Tsukuba, Ibaraki (Japan)) | Imori, H. | Owa, N.
The dissolution of 50 slag samples having different chemical composition in two flooded soils (Eutric Gleysols,local name: Fujimi soil and Kounosu soil) was examined. Si, Ca, Mg and carbonate (sum of CO2, H2CO3, HCO3(-)) concentrations in the soil solution and soil solution pH were measured. In the test using the Fujimi soil, the soil solution was replaced by distilled water (hereafter referred to as soil washing) and then organic compounds, such as glucose and cellulose, were applied to the soil in order to study the effects of depletion of Ca and Mg in the soil solution and CO2 gas supply on the Si dissolution from the slags and soil solid phase. The results obtained were as follows: (1) the soil solution pH and the Ca concentration were positively correlated with the ratio of alkalinity content to 0.5 M HCl-soluble SiO2 content of the slags applied to the soils (A/Si ratio). (2) the si concentration in the soil solution was negatively correlated with the A/Si ratio. This result could be attributed to the increase in si adsorption by the soils which was caused by the increase in the soil solution pH. It was also considered that the increased pH and the increased Ca concentration reduced the solubilities of the slags. (3) the Si concentration was decreased by the soil washing but increased by the subsequent addition of the organic compounds. This increase in the Si concentration was large in the slag application treatments, especially in the case of the application of the slags with a high A/Si ratio, as compared with no slag treatment. (4) It was indicated that the ability of the soil which received the slags to supply silicic acid to the soil solution was enhanced by the decrease in the Ca and Mg concentrations in the soil solution and/or the soil solution pH
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