Long-term effects of inorganic fertilization and organic amendments on soil organic matter and soil microbial properties in Andisols

Abstract

Soil organic matter level, microbial biomass C and N, mineralizable C and N, and dehydrogenase activity were studied in soils from a field experiment under rice-barley rotation receiving inorganic fertilizers and a combination of inorganic fertilizers and organic amendments for the last 17 years. The amounts of soil organic matter and mineralizable C and N increased with the application of inorganic fertilizers. However, there were greater increases in these parameters when farmyard manure, cow dung slurry and pig slurry were applied along with inorganic fertilizers. Microbial biomass C and N increased significantly with the addition of pig slurry along with inorganic fertilizers (536 mg kg−1 soil) than unfertilized soil (241 mg kg−1 soil). The dehydrogenase activity of soil also increased significantly with the addition of organic manures along with inorganic fertilizers. The results indicated that the improvement in organic matter, microbial activities and crop yields due to use of inorganic fertilizers along with organic manures can help in sustaining the long-term productivity of the soil.