Effect of Row Spacing and Frequency of Weeding on Weed Infestation, Yield Components, and Yield of Rice (Oryza sativa L.) in Bench Maji Zone, Southwestern Ethiopia

A field experiment was conducted in Bench Maji Zone at Guraferda district during the 2020 main cropping season to assess the effect of row spacing and frequency of weeding on weeds, yield components, and yield of rice and to estimate the economic feasibility of weed control practices of rice. Factorial combination of three-row spacing (20, 25, and 30 cm) and six weeding frequencies (one-hand weeding and hoeing at 2, 3, and 4 weeks after emergence, two-hand weeding and hoeing at 2 and 5 weeks after emergence, and weed-free check and weedy check) were laid out in randomized complete block design with three replications. Weed control efficiency, days to 50% heading, days to 90% physiological maturity, plant height, and straw yield were significantly affected by weeding frequencies but not by row spacing. Significantly higher panicle length (24.07 cm), number of productive tillers (209.08 m−2), number of kernels per panicle (252.22), grain yield (4303.0 kg·ha−1), aboveground dry biomass (10295.4 kg·ha−1), and harvest index (40.79%) were observed under 25 cm row spacing, compared with 20 and 30 cm. Significantly higher panicle length (25.81 cm), number of productive tillers (257.71 m−2), number of kernels per panicle (172.33), thousand kernels weight (35.44 g), grain yield (5226.7 kg·ha−1), aboveground dry biomass (11696.3 kg·ha−1), and harvest index (44.92%) were recorded under complete weed-free check plots. However, the highest net return (46,394.87 ETB·ha−1) was obtained from the combination of 25 cm row spacing and two-hand weeding and hoeing at 2 and 5 weeks after emergence, as the cost of maintaining weed-free plots was much higher. Thus, practicing two-hand weeding and hoeing at 2 and 5 WAE and 25 cm row spacing was found to be both agronomically and economically feasible for Rice (NERICA-4) production in the Guraferda area.