Decoding the link between bacterial diversity and enzymatic activities of soil from Cymbopogon flexuosus growing dryland

Abstract

The rhizospheric microbial communities and enzymes involved in nutrient mineralization play a vital role in plant and soil health particularly under abiotic stress conditions. Hence, the investigation has been made on the activities of enzymes involved in carbon, nitrogen, phosphorus, and sulfur cycles and metabolic potentials microbial communities of rhizospheric soil of drought-affected areas planted with Cymbopogon flexuosus (lemongrass). The slips of C. flexuosus were planted in the six drought-affected areas of India along with one irrigated region as control following randomized block design. The pH of soils varied from 5.7 to 9.4, whereas, microbial biomass content ranged from 80 μg g−1 (sodic soil) to 813 μg g−1 (black humus granitic soil) μg g−1. Enhanced enzymatic activities were found after two years at all the experimental sites planted with C. flexuosus. In comparison with the drought-affected site, higher microbial diversity (highest Shannon Index) was observed at the irrigated site. The results showed that soil microbiota was dominated by Proteobacteria followed by Firmicutes and Acidobacteria, whereby, Methylobacterium, Escherichia-Shigella, Sphingomonas, Microbacterium, and Brevibacillus were the dominant genera in the study zone. Acidic soils (pH: 5.7) were observed to have a relatively higher abundance of Acidobacteria, while, alkaline soils (pH: 9.4) demonstrated a higher relative abundance of Proteobacteria. The dominance of Escherichia-Shigella and Sphingomonas was observed in all drought sites and these microbes are involved in carbon metabolism. The relative abundance of Methylobacterium was higher in soils having higher microbial biomass and carbon content. Results revealed that despite the homogenizing effect of the lemongrass cover, the soil pH accounted for an important fraction of the variance of microbial composition and enzymatic activity.