Evaluation of the Impact of Herbicides on Soil Characteristics and Grain Yield of Transplanted Rainfed and Irrigated Rice Farming Systems in Makurdi Benue State, Nigeria

Abstract

Herbicides play a vital role in rice production by managing weed growth that competes with crops for essential resources such as nutrients, water, and light. Understanding how herbicide application influences soil properties and rice productivity in these systems is crucial for sustainable agriculture and informed management decisions aimed at boosting rice yield while conserving soil health. This study evaluated the impact of integrated pre- and post-emergence herbicide applications on soil physicochemical properties and grain yield in transplanted rainfed and irrigated rice farming systems in Makurdi, Benue State, Nigeria. The experiment was conducted during the 2024 cropping season using a randomised complete block design with eight treatments, including controls, manual weeding, and combinations of pendimethalin, Solito 320 EC, and Patriarc herbicides at varying rates. Soil samples and yield data were collected from plots under both rainfed (wet season) and irrigated (dry season) conditions. Data were subjected to analysis of variance (ANOVA) using Genstat Release 3.1 and R statistical software. Results showed herbicide treatments significantly influenced soil texture, bulk density, porosity, water holding capacity, and chemical properties such as pH, organic carbon, total nitrogen, and exchangeable bases. High herbicide rates generally reduced  organic carbon and nutrient availability, while moderate applications and manual weeding improved soil porosity and aggregation. Irrigated soils exhibited lower bulk density and higher nutrient contents compared to rainfed soils, consistent with enhanced moisture regimes supporting better soil conditions. Grain yield was significantly higher in plots treated with combined herbicides, exceeding 6 t/ha, compared to controls (~0.5 t/ha) and manual weeding (~4.5 t/ha), indicating effective weed control enhanced productivity in both systems. Correlation analyses highlighted contrasting soil compaction effects under irrigation versus rainfed environments, emphasising the need to balance herbicide use to preserve soil health while maximising yield. This study underscores the importance of optimising herbicide regimes tailored to local soil and water management conditions to sustain rice production and soil fertility in tropical agro-ecosystems like Makurdi.