Effects of Land Preparation Timing and Weed Management Strategies on Weed Dynamics, Yield, and Profitability of Rainfed Lowland Rice

Abstract

The study aimed to evaluate the effect of the timing of land preparation on the weed population of transplanted rice, identify and document the major weeds, evaluate the most effective weed management for transplanted rice in a rainfed ecosystem, and conduct a cost and return analysis. We evaluated four land-preparation timings and three weed controls in a field experiment. The results showed that the major weed species observed at 25 DAT were T. portulacastrum, S. zeylanica, E. crus-galli, and C. difformis, which were unaffected by the timing of land preparation. Five major weed species: A. sessilis, E.crus-gali, I. aquatica, S. zeylanica, and P. virginiana were observed at 55 DAT. S. zeylanica was

the most dominant weed observed in plots with hand weeding at 30 DAT. Herbicide application (Bispyribac Sodium) at 30 DAT significantly reduced S. zeylanica compared with hand weeding alone at 30 DAT. A combination of proper land-preparation timing and weed control also reduced the dominant weed species. Land preparation timing did not significantly affect grain yield; however, it influenced crop growth, weed dynamics, and economic returns. Among the treatments, single plowing two weeks before harrowing and final leveling (TLP2) produced the highest net income and return on investment (ROI), indicating that moderate land preparation provided better economic efficiency under rainfed conditions. The study highlights the importance of integrating appropriate land-preparation timing with effective, cost-efficient weed-management strategies to improve productivity and profitability in rainfed lowland rice systems.