Crop residue heterogeneity: Decomposition by potential indigenous ligno-cellulolytic microbes and enzymatic profiling

The continuous depletion of fossil resources, energy-crisis and environmental pollution has gained popularity for careful selection of suitable microbial consortium to efficiently decompose crop residue and facilitate nutrient cycling. While crop residue is commonly incorporated into soil, the impact of the heterogeneity of residue on decomposition and biological mechanisms involved in extracellular carbon (C) cycle related enzyme activities remain not fully understood. To address this problem, an incubation study was conducted on chemical heterogeneity of straw and root residue with indigenous ligno-cellulolytic microbial consortium on extracellular enzymes as their activity is crucial for making in-situ residue management decisions under field condition. The activity of extracellular enzymes in different substrates showed differential variation with the type of enzyme and ranged from 16.9 to 77.6 µg mL⁻¹, 135.7 to 410.8 µg mL⁻¹, 66.9 to 177.1 µg mL⁻¹ and 42.1 to 160.9 µg mL⁻¹ for cellulase, xylanase, laccase and lignin peroxidase, respectively. Extracellular enzyme activities were sensitive to heterogeneity of biochemical constituent's present in straw and root residues and enhanced the decomposition processes with indigenous ligno-cellulolytic microbial consortium (Bacillus altitudinis, Streptomyces flavomacrosporus and Aspergillus terreus). Correlation matrix elucidated A. terreus and B. altitudinis as potential indigenous ligno-cellulolytic microbial inoculant influencing soil enzymatic activity (p < 0.001). This research work demonstrates a substantial impact of chemically diverse crop residues on the decomposition of both straw and root. It also highlights the pivotal role played by key indigenous decomposers and interactions between different microorganisms in governing the decomposition of straw and root primarily through release of extracellular enzyme. Consequently, it is novel bio-emerging strategy suggested that incorporation of the crop residues under field conditions should be carried out in conjunction with the potential indigenous ligno-cellulolytic microbial consortium for efficient decomposition in the short period of time under sustainable agriculture system.