Journal of Agriculture & Life Sciences

Effect of Herbicide (Pendant) Concentration on Arachis Nodular Rhizobial Microbiota Viability
J.H. Doughari, T. Madani

Abstract
Increasing excessive application herbicides in farming results to accumulation of the chemicals to toxic levels in the soil resulting in harmful effects to microorganisms, plants, wildlife and man. This study investigated the effect of various concentrations of the herbicide pendant on Arachis nodular rhizobial microbiota viability. Soil samples (1.5 kg) in different pouches were treated with different concentrations [x 0.5 %, x 1.0 % (recommended dilution), x 1.5 %, x 2.0 % and x 2.5 % v/v] of the herbicide and population of rhizobia in the root nodules of Arachis hypogea using Most Probable Number (MPN/ml). Rhizobium leguminosarum from crushed A. hypogea nodules was isolated on Rhizobium selective medium. A. hypogea seed germination commenced after 3 days of planting for the recommended (x 1.0 % v/v) as well as other lower herbicide concentrations (x 0.5 % and x 1.5 % v/v) and for the control (without herbicide), but for pouches containing higher herbicide concentrations (x 2. 0 and x 2.5 %), germination commenced only after 5 days. While there was normal growth of Arachis hypogea treated with lower herbicide concentrations, there was stuntedness and discoloration in the leaves for seedlings treated with higher herbicide concentrations. Also, rhizobial population of the root nodules decreased with increased herbicide concentration in the order; control (4600 MPN/ml) > recommended (2100 MPN/ml) > higher concentration (200-360 MPN/ml). Inappropriate herbicide application influences negatively rhizobial microbiota of soil with a cascading effect on crop yield. Strict regulation on the use of herbicide and adequate training of workers and farmers for effective and safe use of the herbicide is necessary.

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