Herbicide efficacy and non-target toxicity in highland rainfed maize of Eastern Ethiopia

Abstract

Heavy weed infestation poses a major challenge to maize production in Ethiopia. Weed control is practised through hand-weeding or hoeing, both of which are neither adequate nor timely. This study attempts to develop an efficient and economical way of controlling weeds through the use of herbicides, and to evaluate the herbicides for toxicity to microorganisms, particularly plant–parasitic nematodes. Twelve treatments, in a randomised block design with three replications, were used. Sequential applications of atrazine (i.e. atrazine 2.0 kg/ha at pre-emergence followed by 0.25 kg/ha at post-emergence; atrazine 1.0 kg/ha at pre-emergence followed by 0.25 kg/ha at post-emergence) were found to significantly reduce the dry weights of monocots, dicots and total weeds. Pre-emergence applications of atrazine at 2.0 and 1.0 kg/ha, and of pendimethalin at 2.0 kg/ha, reduced dry weight only in dicot weeds. Sequential applications did not inhibit bacterial population growth, but were toxic to plant–parasitic nematodes and fungi, causing a reduction in their abundance. Sequential applications, and single application of atrazine 2.0 kg/ha at pre-emergence, resulted in maize yields, net benefits and benefit–cost ratios higher than other treatments.