Effect of Tillage System, Herbicide Weed Management, and N-Split Application on Yield and Milling Quality of Irrigated Rice (Oryza Sativa L.) in the Guinea Savannah Zone of Ghana

In the Guinea Savannah agro-ecological zone of Ghana, rice productivity is hampered by suboptimal tillage practices, ineffective weed management, and poor soil fertility. To address these constraints, a field experiment was carried out in Botanga and Golinga to evaluate the effects of tillage systems, herbicide application methods, and N-split fertilizer regimens on irrigated rice (Oryza sativa L.) yield and milling quality. The study used a 3 x 3 x 3 factorial design arranged in a split-split-plot with three replications. Results revealed that soils at both sites were clay loam, slightly acidic (pH 5.10), with low total nitrogen (0.10%), available phosphorus (2.88 mg/kg), and exchangeable cations. Amon the treatments, minimum tillage combined with pendimethalin + triclopyr significantly reduced weed density compared to other combinations. The application of pendimethalin (0.40 kg a.i. ha⁻¹) + triclopyr (0.03 kg a.i. ha⁻¹), coupled with 120 kg N ha⁻¹ split into four applications, enhanced tillering (19 and 17 tillers per hill at Golinga and Botanga, respectively, at 6 weeks after planting). This treatment also produced the highest filled spikelets per panicle and maximum 1000-grain weight at both locations. The same fertilizer and herbicide combination yielded the highest grain production, 8,487 kg/ha at Golinga and 8,016 kg/ha at Botanga, and showed positive correlations with panicle weight, seeds per panicle, and straw weight. Additionally, it resulted in the highest unbroken grain recovery (7.5 mm) and benefit-to-cost ratio. The study recommends applying pendimethalin + triclopyr at 0.40 kg a.i. ha⁻¹ combined with 120 kg N ha⁻¹ split into four doses to maximize rice yield, quality, and income. Overall, the research underscores the significance of tailored, evidence-based agronomic practices to improve rice productivity in Ghana’s Guinea savannah zone.