This work aimed to determine the interference of weed communities in crop yield characteristics, under no-till and conventional till systems. The soybean cultivars used in these experiments were M-SOY - 6101 and CD 201 for conventional and no-till, respectively. The notill system weed community reached its maximum value of 377 plants m-2 28 days after soybean emergence. Maximum dry matter accumulation was 365.7 g m-2, 118 days after emergence, with the main plants being Alternanthera tenella, Cenchrus echinatus and Bidens pilosa. Under the conventional till system, maximum density was 161 plants m-2, 18 DAE and 406.7 g m² of dry matter accumulation at 118 DAE, with the main plants being A. tenella, Senna obtusifolia and Panicum maximum. Accepting losses of 5% in soybean productivity, the CPPI values were estimated to range from 33 to 66 DAE for the no-till system and from 3476 DAE for the conventional till system. Weed interference during the full crop cycle reduced, in average, 46 and 32% of productivity under the no- till and conventional till systems, respectively. No effects were observed on plant height, first pod insertion height, and number of pods per plant due to the presence of weed community.
competition; Glycine max; control periods
