Interferência de plantas daninhasna cultura do sorgo sacarino

Abstract

This is a phytosociological study which determined the critical period of weed interference in sweet sorghum crops. The experiment was a randomized block design with three replications. Treatments consisted of increasing periods of control or coexistence of weeds in different phenological stages of crop growth: 0-3 (V3), 0-5 (V5), 0-7 (V7), 0-9 (V9), 0-11(V11) fully expanded leaves and 0-R5 (harvest). The weed community was evaluated for the number of individuals and their correspondent dry mass accumulation, for each weed population in different periods of coexistence. Sweet sorghum was harvested at 101 days after emergence, when we measured plant height, stem diameter, total soluble solids (oBrix) according to the periods of coexistence between crop and weeds, besides the yield of stems. Commelina benghalensis and Panicum maximum were the two species of greater relative importance in the area. The lack of weed control, during the crop cycle, led to an increase in total soluble solids (oBrix) and reduction by 9 and 25% in plant height and stem diameter, respectively, when compared with the hoed control throughout the cycle. Accepting losses of 5% in stem yield, the critical period of weed interference corresponded to the period between phenological growth stages V3 and V11.