Vol. 13 No. 2
Microbial phosphate solubility as influenced by pyrethroid insecticide in tea soil of the Himalayan Terai region of West Bengal
Author(s): A. C. DAS
Abstract: An experiment was conducted under laboratory conditions to investigate the effect of four pyrethroid insecticides, viz. cypermethrin, deltamethrin, fenvalerate and permethrin at rates of 225, 200, 225 and 210 g a.i. ha-1, respectively, on growth and activities of microorganisms, phosphate solubility and its availability in tea soil of West Bengal, India. Insecticides in general, had a deleterious effect on bacteria and actinomycetes, being the highest with fenvalerate (11%) followed by permethrin (10.3%) for bacteria and with permethrin (13.9%) for actinomycetes. Fungi propagules were highly increased with permethrin (51%) followed by fenvalerate (32.6%). Cypermethrin and deltamethrin had no significant effect on the proliferation of microorganisms, excepting fungi with deltamethrin. Phosphate solubilizing capacity of the soil was badly affected with fenvalerate (16.3%) and permethrin (15.2%). Application of insecticides had a meager positive effect on the retention of total phosphorus, while availability of soluble phosphorus remained unchanged in the treated soils.
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