Response of microorganisms and soil enzyme activityin groundnutrhizosphereunder different nutrient management systemand its invitroevaluation of antagonistic efficiency against foliar pathogen Alterneriaporri

The effect of different nutrient management practices on microorganisms and soil enzyme activities in groundnut
rhizosphere was investigated in the present study. This research faced challenges such as variability in soil microbial
populations under different farming systems and the difficulty of isolating effective biocontrol agents. Despite these
challenges, the study provides significant contributions by identifying specific bacterial isolates with potential
antagonistic effects against foliar pathogens and offering insights into the efficacy of nutrient management practices.
The effect of different nutrient management practices on microorganisms and soil enzyme activities in groundnut
rhizosphere was investigated in the present study. Depending on the present farming trend, the microbial distribution
in soil practices with natural farming, organic farming, conventional farming and farmer’s practice was analyzed. A
total of twenty soil samples at different intervals were collected from different types of management practices under
groundnut at Zonal Agricultural and Horticultural Research Station (ZAHRS), Hiriyur, Karnataka, India.Three years
pooled data revealed that, Among the different nutrient management practices at harvest stage, the chemical farming
practice (RPP) showed higher number of bacteria, (42.07 x 10-5cfu g-1 soil), fungi (13.22 x 10-4cfu g-1 soil),
actinomycetes (8.07 x 10-3cfu g-1 soil) and beneficial organisms viz., Rhizobiumsp,Azotobactersp, PSB,
Pseudomonassp(11.16,12.08, 8.33 and 13.43 x 10-5cfu g-1 soil respectively) and Trichodermasp (2.25 x 10-4cfu g-1
soil).Similarly, soil enzyme activities viz., dehydrogenase (90.35 µg TPF g-1 soil day-1), Urease (35.65 µg NH4+ g-1
soil 2 hr-1) acid and alkali phosphatase (20.54 and 16.18 µg PNP g-1 soil) compared to other practices. A total of
thirty twobacterial isolates.e. eight isolates from each practice were selected based on their morphological and
biochemical characteristics and tested their antagonistic effect on groundnut foliar pathogen Alterneriaporri under in
vitro dual culture bioassay technique.Out of that, only seven isolates from different practices were inhibited foliar
pathogen Alterneriaporri. The maximum inhibition ofpathogen by NA-2 isolate from natural farming practices (47.02
%), followed by Azo-2 isolate from organic farming practice (46.30 %), NA-1 isolate from chemical farming
practices (41.11 %) and PSB -1 isolate from organic farming practice (40.74 %). These seven isolates were identified
at the species level based on the 16S rRNA gene. Molecular identification based on 16S rRNA gene revealed seven
species belonging to Pseudomonas, Serratia, Azotobacter, and Bacillus genus.