The Effect of the Application of Different Rates of Herbicides on the Growth and Yield Component of Zea mays L

Background: Weeds are responsible for low crop yield, and responsible for the large gap between the potential and actual yield per hectare. The traditional manual method of weed control in Nigeria has become very difficult and expensive, because of the cost of hiring labor, particularly during the peak cropping period, due to increasing rural-urban migration. This has encouraged the use of herbicides in weed control, even by untrained illiterate farmers, hence the need to assess the effects of the use on yield. This study assessed the effects of the application of different concentration of herbicides on the growth and yield of maize, cultivated in succeeding years. Materials and methods: The study was carried out in a plot of land at the University of Port-Harcourt in 2013 and 2014, using a randomized complete block design with three replicates, and plot size of 2m x 2m. Glyphosate was used to prepare the experimental plots, while different application doses of primextra dual gold (atrazine and metolachlor) were applied to the plots, after planting the maize. The control plot was not treated with the herbicides. The growth and yield parameters of the maize planted in the plots were assessed through the physio-chemical characteristics of the soil, the germination count, leaf count, height of maize plant, and the yield of maize at harvest. Results: The application of the herbicides resulted in improvements in the growth and yield parameters of the maize. The parameters in the plots in which the herbicides had been applied at or below the manufacturer’s recommended dose (2.11ai/ha) were comparable to those of the control; and then significantly decreased in the plots in which the herbicides were applied in overdose. The parameters were also higher in the first phase of the study, compared to the second phase that took place one year later in the same plots. There was also a reduction in the organic matter and exchangeable minerals content of the soil in the second phase of the study. Conclusion: The application of herbicides for weed control, up to their recommended doses resulted in a one-off improvement in the growth and yield parameters of the cultivated maize crop. Efforts are therefore needed to properly educate farmers