Distribution of the Si-deficiency rice soil in Hubei Province

There are about 1 million ha of Si-deficiency paddy soils in Hubei Province. Practically, it is essential to study the Si nutrient status in those Si-deficiency rice soil and its regional distribution before the application of Si-fertilizer. According to the analysis of 50 rice soil samples which collected from 20 counties/cities in Hubei Province, the available Si content in rice soils derived from different parent materials varied greatly. The Si content from high to low was in sequence of limestone, redpurplish sandy shale with carbonate, alluvium and lacustrine deposits, quaternary period red clay, granitic gneiss, and sandy shale. In addition, the Si content in rice soil was remarkably related with its pH. It seems that the pH 6.5 might be a demarcation line that divided the supplying Si ability of rice soils into the low and high categories (Table 1). Integrating the results with a critical soil Si-deficiency as 100 mg/kg, the evaluation index of soil Si supplying capability of a rice soil