Potential organic amendments for improving productivity and associated biological properties of low carbon soil.

Applying organic amendments with high carbon (C) content can indeed improve soil quality and increase crop yields. The objective of this 4-year field study was to evaluate the effects of three fertilizer-N application (N0, N75, and N100) levels in main plots and five levels of organic amendments incorporation (farmyard manure, poultry manure, press mud, rice straw compost and no manure) in wheat in sub-plots on soil biological properties, and crop yields in a low C sandy loam (<italic>Typic Ustochrept</italic>) soil. The application of fertilizer-N and organic amendments significantly increased all the soil enzyme activities as compared to the control. In contrast, the results of microbial biomass carbon, phenoloxidase, and peroxidase activity were significantly higher in farmyard manure treated plots by 64.6, 46.2 and 17.7%, respectively than control. Principal component analysis (PCA) suggests that dehydrogenase, xylanase, phenol oxidase, peroxidase and alkaline phosphatase can serve as sensitive indicators and were contribution to soil quality index by 42.5%, 11.3%, 46.8%, 22.6%, and 3.7%, respectively. Results suggest that locally available organic manures can be potential soil amendments to improve biological properties and enhance crop productivity under integrated nutrients management practices in rice-wheat cropping systems. [ABSTRACT FROM AUTHOR]