Microbial diversity of soils under different cropping systems in semi-arid zones of Haryana

Soil management practices such as crop rotation and crop production inputs affect soil microbial communities. In this study, we made an attempt to demonstrate distinctive effects of specific crop rotation on microbial communities by determining microbial populations and BIOLOG assay in their rhizosphere and non-rhizosphere soil. Effect of eight different crop rotations (being popularly adopted in Haryana, India) was studied on soil microbial communities. Increase in number of diazotrophs was observed in the rhizosphere of cotton-wheat rotation, while total bacteria and P-solubilizers were maximum in pearl millet+clusterbean-wheat rotation on their respective media after one month of sowing during summer and winter seasons. On the basis of carbon-source utilization pattern using BIOLOG assay, these cropping patterns also had maximum microbial activity at all the stages of plant growth. Cluster analysis based on quantitative and qualitative utilization of a carbon source revealed more microbial diversity during summer season as compared to the winter season. The rhizospheric samples collected after the harvest formed entirely different sub-cluster as compared to the samples collected before sowing and after one month of sowing, clearly indicating the changes in the microbial community after the harvest of crop.