Cereal-legume intercropping oft en results in increased productivity, weed suppression, and N supply. Th e agronomic and economic benefi ts of maize-bean (Zea mays L. -Phaseolus vulgaris L.) intercropping were studied for 5 yr in a complete factorial with: 0, 1, and 2 weedings (W0, W1, W2); and single (MB) and double (MBB) rows of bean alternated with one row of maize. Sole crop maize and bean were included. Weed infestation in intercrop was 30% less compared with sole crop bean but with inconsistent diff erences across years. Weed biomass was 13% less with MBB compared with sole-cropped maize. Ears m -2 were 55% more in seasons with better rainfall compared with 1999 and 16% more with W1 or W2 compared W0. Mean maize grain yield was 3.74 Mg ha -1 . Weeding frequency (WF) eff ect on maize grain yield was inconsistent across years but yield was 75% more with W2 compared with W0. Overall, maize grain yield was 19% more with MB compared with MBB but the eff ect was signifi cant in 1997 only. Mean bean yield was 1.07 Mg ha -1 and was inconsistently aff ected by treatments across years. Bean yield was on average 52 and 67% more with W1 and W2, respectively, compared with W0, and 35% more with MB compared with MBB. Intercropping resulted in land equivalent ratios (LER) of 1.0 to 2.4 with a WF eff ect. Mean net income (NI) was greatest with MB and W1. Overall, intercropping suppressed weeds and was more productive and economical than sole crop production.

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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.