The effect of Herbicides on Residual Effects of Atrazine under Conservation Agriculture

Abstract

An experiment was set up to evaluate the residual effect of atrazine in cowpea production under conservation agriculture. The trial was superimposed on a previous herbicide trial of a maize crop in 2012/2013 season. The experiment was laid out in a randomized complete block design with three replicates and four treatments as follows; 1. control (manual weeding), 2. Atrazine (3.6 litres/ha), 3. Atrazine (3.6 litres/ha) + glyphosate (2.5 litres/ha) and 4. Atrazine (3.6 litres/ha) + glyphosate (2.5 litres/ha) + metolachlor (1 litre/ha). Herbicide treatment was carried out at planting time and manual weeding at 10 cm weed height. Data collected include: germination percentage, weed counts and weed biomass, cowpea biomass, pod length and cowpea yield. The herbicidal treatments showed a significant effect (p<0.05) on pod length and cowpea yield. The control plot had the highest pod length of 17.03cm and atrazine alone had the least of 15.77cm. A combination of three herbicides had the highest yield of 1.2t/ha and atrazine alone had the lowest yield of 0.9t/ha. No significant (p>0.05) effects were recorded on percentage germination, weed counts and weed biomass as well as on cowpea biomass. Tank mixing of two or more herbicides is recommended when using atrazine to reduce residual effect and further research is recommended under different soil types with different climatic conditions.