The availability of Si in acid soil was decreased by increaslng soil pH, and that in alkaline soil was increased by decreasing the soil pH.

• 强酸性土、酸性土，质地偏砂土壤常是缺硅土壤; 提高酸性土的pH，硅的有效性下降，降低碱性土的pH，土壤硅的有效性增强。