Assessment of Weed Infestation and Control Methods in Upland Rice Production in Anambra State

This study assesses weed infestation patterns and evaluates the effectiveness of different weed control methods in upland rice production in Anambra State, South East Nigeria. Weed competition is one of the most significant constraints on rice productivity in upland environments, with yield losses of 40 to 80 percent reported when weeds are left uncontrolled during the critical weed-free period. Anambra State's upland rice farming communities rely predominantly on labour-intensive hand weeding, which is becoming increasingly difficult due to rural labour shortages. This study uses a split-plot field design at the Federal College of Agriculture Igbariam, comparing five weed control treatments: no weeding, one hand weeding at three weeks after planting, two hand weedings at three and six weeks, pre-emergence herbicide pendimethalin, and post-emergence herbicide propanil. Weed density, weed dry weight, rice growth indices, and grain yield are measured at two and six weeks and at harvest. Findings reveal that two hand weedings produce the highest grain yield of 3.4 tonnes per hectare, closely followed by post-emergence herbicide at 3.2 tonnes per hectare. A single hand weeding produces significantly lower yield, highlighting the importance of the second weeding. Unweeded plots yield only 0.9 tonnes per hectare. The study concludes that effective weed management is critical for acceptable rice yields in Anambra State. It recommends post-emergence herbicide as a labour-saving alternative that maintains yield competitiveness.

Keywords: weed control, upland rice, Anambra State, herbicide, weed-free period.