This work aimed to carry out a phytosociological study and to determine the critical interference periods of the weed community on direct sowing beet. The treatments were weedy and weed-free increasing weekly periods, starting at the second week after sowing. The weed community was evaluated based on the number of individuals and their correspondent dry mass accumulation, for each weed population and evaluated period. The beet was harvested 91 days after sowing, followed by transversal diameter and marketable yield evaluation. The weed communities were composed mainly by Amaranthus viridis, Coronopus didymus, Galinsoga parviflora, Nicandra physaloides and Solanum americanum, and the populations were very similar. The period before weed interference and the entire period of weed interference prevention were 14 and 36 days after sowing, respectively. Beet yield in the weed-free treatments was 37.99 t ha-1and weed interference can be over 90%.
Beta vulgaris; weed competition; weed interference; weeds
