Study on the activity and diversity of bacteria in a New Gangetic alluvial soil (Eutrocrept) under rice-wheat-jute cropping system

Abstract

Aim: Soil microorganisms play an important role in sustaining soil health and long term productivity by performing major soil functions like decomposition of organic matter, nutrient cycling and formation of soil aggregate etc. The main objective of the present investigation was to study the long term (42 years) effect of different management practices on the activity and diversity of bacteria isolated from a New Gangetic alluvial soil with rice-wheat-jute cropping system. Methodology: Soil samples were collected from five different management practices viz., fallow, control, 100% recommended dose of NPK, 150% of recommended dose of NPK and 100% recommended dose of NPK plus farmyard manure under 42 years old long term fertilizer experiment with rice-wheat-jute cropping system at Central Research Institute for Jute and Allied Fibres, Barrackpore, West Bengal. Soil samples were analysed for microbial populations using various media, microbial biomass carbon, dehydrogenase, FDA hydrolase, acid and alkaline phosphatase activity of soil. Bacterial diversity was analysed by PCR-RFLP of genomic DNA of isolates using Hae III restriction enzyme. Results: Enumeration of soil microbes was done by standard method of serial dilution and spread plate technique using different media. Highest bacterial population was found with 100% NPK+FYM treatment on nutrient agar media Microbial biomass carbon content under different management practices varied from 221 to 447 mg kg-1 soil and highest was found with 100% NPK+FYM treatment. For all the four enzyme activities, highest value was found with integrated treatment and lowest was with control treatment. Dendrogram derived from the distance matrix by UPGMA, a total of 35 clusters were recorded for 59 bacterial isolates. Interpretation: Integrated management practices with balanced use of mineral fertilizers and organic manures sustain the microbial activity and diversity and maintain soil health.