Vol. 8 No. 1
Effect of herbicides on microbial biomass in relation to availability of plant nutrients in soil
Author(s): A. C. DAS, S. J. DAS AND S. DEY
Abstract: An experiment was conducted under laboratory conditions to investigate the effect of three herbicides, viz., fenoxaprop, pendimethalin and paraquat either separately or in a combination of two, at their field application rates (50 g, 1.0 kg and 1.0 kg a.i. ha-1, respectively) on the changes of microbial biomass carbon, nitrogen and phosphorus as well as transformations of plant nutrients in an alluvial soil collected from Cooch Behar, West Bengal. Application of herbicides significantly increased the microbial biomass carbon, nitrogen and phosphorus which resulted greater availability of plant nutrients in soil. The microbial biomass carbon was highly induced due to the combined application of the herbicides followed by single application of fenoxaprop and paraquat Pendimethalin alone recorded maximum stimulation to the microbial biomass nitrogen while microbial biomass phosphorus was highly induced under the combined application of fenoxaprop and paraquat followed by single application of paraquat. The highest retention of organic carbon was recorded with pendimethalin when applied alone or in a combination with fenoxaprop while paraquat in combination with fenoxaprop and pendimethalin retained more amount of total nitrogen. The stimulation of available nitrogen (exch. NH4+ and soluble NO3-) was highest under the combined application of fenoxaprop and pendimethalin followed by the single application of fenoxaprop. In case of availability of phosphorus in soil, the stimulation was highest with the single application of paraquat followed by the combined application fenoxaprop and pendimethalin.
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