Development of biological soil quality indicator system for subtropical China

The hilly red soil region of subtropical China is a major rice producing area, where over-exploitation and non-agricultural uses of paddy soils have decreased soil quality and rice productivity. Our objectives were to develop and evaluate a soil quality assessment protocol for Yujiang County in Jiangxi Province. A variety of soil samples, representing the spatial homogeneity in 114 paddy fields, were collected and analyzed for several chemical and physical properties. Pearson correlation analysis between rice yield and the various soil properties was used to identify potential soil quality indicators. Principal component analysis (PCA) was then used to group the indicators into appropriate soil quality factors. A minimum data set (MDS) including soil organic matter, available nitrogen, available phosphorus, slowly available potassium and sand content accounted for 77.9% of the quality variation among soils. A soil quality index (SQI) was calculated using the Integrated Quality Index (IQI) equation. Significant correlation between the SQI and rice yield indicated the index had high biological significance for Jiangxi province and other paddy areas with similar soils.