Characterization and dynamics of lignocellulosic components, enzyme activities and microbial populations in diverse crop residues during decomposition

In intensive cropping systems, limited understanding of how residues with contrasting biochemical qualities decompose leads to nutrient immobilization, poor nutrient release synchrony and persistent residue burning challenges. The decomposition dynamics of various crop residues displayed unexpected variations at both the early and late stages, with the precise underlying factors for these differential responses to diversity remaining unclear. We hypothesized that the chemical composition and biochemical diversity of crop residues specifically difference in lignin, cellulose, hemicellulose, protein, phenol, nitrogen content and C: N ratio would substantially influence their decomposition dynamics and associated microbial and enzymatic responses at different time points. In an incubation experiment, we examined nine treatments, each with three replicates: maize stover (T₁), rice straw (T₂), cotton stalks (T₃), redgram stalks (T₄), greengram residue (T₅), blackgram residue (T₆), sunhemp residue (T₇), soybean residue (T₈), and sorghum stover (T₉). We closely monitored the transformation of lignocellulose, total phenols and proteins in these crop residues using the litter bag method alongside measurements of soil enzyme activities and microbial population dynamics. Results revealed distinct decomposition patterns, where legume-based residues (sunhemp (T₇), greengram (T₅), blackgram (T₆) and soybean (T₈)) exhibited rapid degradation of lignocellulosic fractions and protein content within 60 days, associated with early peaks in microbial populations and enzyme activities (cellulase, xylanase, laccase and lignin peroxidase). In contrast, residues high in lignin, C:N ratio, lignin: N ratio and phenol: N ratio such as redgram stalks (T₄), maize stover (T₁), rice straw (T₂), cotton stalks (T₃) and sorghum stover (T₉) decomposed more slowly, showing prolonged microbial activity and enzyme induction up to 120 days. Total phenol content initially declined (0-30 days after incorporation) and subsequently increased, reflecting the release and transformation of bound phenolics. Principal component analysis (PCA) revealed that residue biochemical traits, especially nitrogen content, lignin level and phenol content, strongly influenced microbial succession and enzymatic response. Overall, the decomposition sequence of biochemical components followed the order: lignin < cellulose < hemicellulose < proteins, and the enzyme activity followed the order: lignin peroxidase < cellulase < xylanase. These findings emphasize the importance of residue quality in regulating decomposition dynamics and offer actionable strategies for tailoring residue management to enhance nutrient cycling and soil health.