Assessing extracellular enzymatic activity in the soil on addition of root biomass with different biochemical composition.

Biochemical quality of a biomass determines the rate of its decomposition, which ultimately affects the relative microbial communities. Root biomass constitutes a significant fraction of total plant biomass and can play an important role in affecting microbial activity and extracellular soil enzymes when roots have different biochemical composition. To address the pivotal action of biochemical quality, a short-term incubation study was carried out to determine the effect of heterogeneity of root biomass on the functional characteristics of enzyme activities in the soil. Root biomasses of six crops with contrasting chemical composition (Oryza sativa, Zea mays, Gossypium hirsutum, Glycine max, Cajanus cajan and Sesamum indicum) were applied alone as well as in different combinations to a sandy-loam soil incubated under controlled environment condition for 63 days. The enzyme activity peaked on the 42nd day, which ranged from 11.85 to 16.85 µg triphenylformazan and from 9.84 to 13.67 µg p-nitrophenol g-1 h-1 for dehydrogenase and alkaline phosphatase respectively. Among the different root biomasses and their combinations, maximum soil enzyme activity was found for Z. mays (T2) followed by G. max (T4) and G. max + O. sativa (T9). The roots of Oryza sativa (T3), Cajanus cajan (T6) and Cajanus cajan + Oryza sativa (T10) with high contents of hemicellulose and low contents of cellulose showed low enzymatic activity. Cellulose and hemicellulose contents in root biomass are mainly responsible for the enhanced functional diversity of soil microbial communities as well as enzyme activities. [ABSTRACT FROM AUTHOR]

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