Effect of Plowing Frequency and Weeding Methods on Weeds and Grain Yield of Wheat at Arsi Negelle, Ethiopia

The effect of repeated tillage and weed control methods on weed infestation and grain yield of wheat was evaluated at Arsi Negelle, southern Ethiopia, from 1993 to 1995 cropping seasons. Five tillage practices (zero, one, two, three and four times tillage) as main plot and four weed control methods (Duplosan sprayed at 2.5 l ha-1, Duplosan plus one hand weeding at 30 days after emergence (DAE); one and two hand weeding at 30, and 30 and 60 DAE, respectively) as subplots were arranged in split plot design with three replications. Broadleaf weeds comprised 73% of the total weed population in the experimental plots. Effect of tillage and weed control was dependent on year. Increased frequency of tillage reduced weed infestation (r = -0.34**) and increased plant height (r = 0.42**), biomass (r = 0.51**) and grain (r = 0.43**) yields of wheat. Weed density in zero-till and three times plowing was 78 and 35%, respectively, more than four times. Weed density in plots treated with Duplosan alone and its combination with 1HW was 38.4 and 19.5% more, respectively, while it was 5.9% less with 1HW alone compared with 2HW. About 33 and 26% of the total variations in weed infestation were due to tillage and weed control methods, respectively. Grain yield reduction in zero-till and three times plowing was 59 and 21%, respectively, compared with four times’ plowing. Twice weeding reduced weed population by 28% and increased wheat grain yield by 3.3% compared to Duplosan alone. Fifty five, 95 and 43% of the total variations in wheat grain yield in 1993, 1994, and 1995, respectively, were attributed to the regression. Frequent tillage reduced weed infestation and increased grain yield by 11 and 21.9%, respectively, compared to weed control. Generally, four times plowing significantly reduced weed infestation and increased wheat grain yield with considerable economic benefit