Impacts of agro-climates and land use systems on culturable microbial population in soils of the Indo-Gangetic Plains, India.

Abstract

Comprehensive reports on land-use changes and their impact on soil biological properties, specifically microbial population in the Indo-Gangetic Plains (IGP) of India, are lacking. Since IGP is the most fertile land, data on microbial population of IGP may contribute towards the evaluation of various soil quality parameters, disease suppression, organic matter decomposition, plant growth promotion and soil management pattern. To enhance our knowledge on culturable microbial populations in different soil horizons of the agro-ecological sub-regions (AESRs) in the IGP, a study has been undertaken to collect soil samples from the established benchmark (BM) spots of these plains with an objective to investigate the impacts of bioclimates, soil depth, cropping systems, land use systems and management practices on the distribution of culturable microbial population. Bacterial : fungal ratios are significantly different across the land use types. The bacterial and fungal populations are strongly and negatively correlated with soil depth and maximum microbial population (40%) exists in the surface horizon (0–30 cm) than in the subsurface horizon (121–150 cm). Generally, bacterial populations are higher than actinomycetes and fungal populations in all soil profiles of the IGP. Approximately 10% decrease in Shannon diversity index has been observed with increase of 30 cm depth and 89% fall between surface and subsurface profiles. Non-significant difference in microbial population (P < 0.05) is noticed across the management and land use systems. Sub-humid (moist) bioclimatic system recorded higher microbial population than sub-humid (dry) and semi-arid bioclimatic systems. Legume-based cropping system has higher microbial population than cereal or vegetable-based cropping.