Effect of selected herbicides on weed management in sorghum production in Kenya

Weed infestation in sorghum (Sorghum bicolor L. Moench) forms a major biotic stress that needs to be addressed to achieve adequate grain supply to meet increasing industrial demand for sorghum. The aim of this study was to determine the most effective herbicides for weed management in sorghum. A field experiment was conducted at Egerton University in Njoro, Kenya in 2015. The experiment was carried out in a randomized complete block design (RCBD) with nine experimental units replicated three times. Four pre-emergence herbicides namely Lumax (Mesotrine, Metolachlor, Terbuthylazine), Primagram (Atrazine, S - metolachlor), Dual gold (S - Metolachlor) and Sencor (Metribuzin) were tested in the study, in addition to three post-emergence herbicides namely 2,4-D (2,4-D amine salt), Maguguma (Atrazine, S-metolachlor) and Auxio (Bromoxnil, Tembotrine). Positive and negative controls comprised of hand weeding and no weeding. Pre-emergence treatments were applied immediately after sowing while post-emergence treatments were applied 30 days after sowing. Weed density and biomass was determined at 30 and 60 days after sowing. All data were subjected to analysis of variance using SAS version 8.1. Means were separated according to least significant difference (LSD) test whenever the herbicide effects were significant (P d” 0.05). Analysis of variance (ANOVA) revealed significant (Pd”0.05) differences in the effect of the treatments evaluated. Amongst the four pre-emergence herbicides, Sencor (Metribuzin) was the most effective herbicide reducing the weed density by 96% and 95% compared to no weeding and hand weeding, respectively. Thirty days after the application of post emergence treatment, weed densities were reduced by 90%, 80%, 43%, and 26% when 2,4-D, Hand weeding, Maguguma and Auxio were used, respectively. Adoption of Sencor and 2, 4-D in recommended rates will ensure effective weed management and contribute to increased sorghumproduction to meet the increasing industrial demand.