Abstract

A field study on the effect of herbicide (pendimethalin) on soil microbial community was conducted between August to September (2010) on a sandy-loamy soil located at the Federal University of Technology, Crop Science Departmental Farm Gidan-Kwano, Minna, Nigeria. Samples were collected randomly from the experimental farm before and after application of herbicide; on which cowpea was cultivated. Herbicide (Pendimethalin) was applied at below recommended rate, recommended rate and above recommended rate. The result reveals the following herbicide treatments at the recommended rates resulted in decrease in microbial count. High concentration of herbicide treatment resulted in a much lower microbial count compared to soil treated rate, recommended herbicides and none treated soil. The most frequently isolated bacteria from herbicide treated soil are Bacillus and Pseudomonas sp.,while Aspergillus, Rhizopus and Penicillium sp. were the most frequently isolated fungi from treated soils. Cowpea yield was highest in site treated with herbicide at above recommended rate and lowest in the control site. The results revealed that herbicide is an integral part of farming, although it has a significant effect on soil microbial community.

Key words: Herbicide (pendimethalin), recommended rate, recommended rate and above recommended rate.