Two field experiments were conducted at the Experimental Farm of the National Research Centre at Shalakan, Kalubia Governorate, Egypt during the 2005 and 2006 seasons to study the effect of three weed management {hand hoeing twice, butralin+prometryn and unweeded check} as well as six intercropping patterns {two pure stand crops, besides intercropping sunflower: soybean {sun: soy} alternating ridges 1:1, 1:2, 2:1 as well as side: side}. Results
showed that the lowest light intensity was recorded with sole soybean. Hoeing achieved the lowest dry weights of the grassy, broad-leaved and total weeds, but statistically leveled with those of butralin+prometryn in grassy and broad-leaved weeds. The lowest dry weight of grasses was recorded with 1:1 and 1:2 intercropping patterns. Hoeing was the best treatment for promoting sunflower and soybean seed yields/fed. Among the intercropping systems, the
pattern of side: side appeared the highest significant sunflower seed yield than the rest of other intercropping ones and could recover maximum of its sole sunflower yield (81.3 %). The highest LER values, i.e. 1.376 and 1.198 recorded when sunflower and soybean intercropped in side: side and 1:2, respectively. The Aggressivity values indicated that sunflower component was the dominated, while soybean was the dominant one.
