Relationship Among Weed Control, Herbicide Use, and Maize Production

Abstract

Weeds are among the most important biotic factors that limit maize (Zea mays L.) production, outcompeting the crop for light, nutrients, water and space during the entire growing season. Thus, weed management is a crucial part of achieving maize's yield potential; the relative efficacy, economic viability and environmental impacts of various weed control strategies are still under investigation especially in tropical and sub-tropical smallholder farming contexts. In this study, a replicated field experimental design is used to examine the interactions between weed control practices, herbicide application, and maize grain yield for eight treatments: unweeded control, manual weeding only, low and high rate atrazine, low and high rate glyphosate, integrated weed management (IWM) (herbicide application plus manual weeding), and two-pass herbicide treatment. The treatment was repeated four times in a Randomized Complete Block Design (RCBD) for three growing seasons (2021-2023). The density of weeds and weed community composition were measured at 2, 4, 6 and 8 weeks after planting (WAP) while maize grain yield was measured at physiological maturity. Analysis of variance (ANOVA) and Tukey HSD post-hoc tests were used to analyze the data, and regression analyses were performed. Results revealed highly significant treatment effects on both weed density (F₇,₇₅ = 58.4, p < 0.001) and maize grain yield (F₇,₇₅ = 47.3, p < 0.001). The mean maize yield for the integrated weed management treatment (herbicide + manual weeding) (5.24 t/ha) was highest, while the two-pass herbicide treatment (4.95 t/ha) and high-rate glyphosate (4.78 t/ha) were intermediate, with the unweeded control (1.82 t/ha) being the lowest. Regression analysis showed a significant negative relationship between weed density and yield of maize (R² = 0.832, p<0.001). Economic analysis added up the integrated weed management strategy with the highest gross margin (USD 562/ha), which was also found to be the most agronomic. Findings have implications for the promotion of integrated weed management in smallholder maize production systems.