Interferência de plantas daninhas em sorgo sacarino em diferentes espaçamentos no semiárido mineiro

Abstract

This work aimed to make a phytosociological survey, determine the period before interference (PB), the total period of weed interference (TPWI) and the critical period of weed interference (CPWI) in sweet sorghum crop, BRS 506 cultivar. The experiment was carried out at Experimental Farm belonging to EMBRAPA/CNPMS, in Nova Porteirinha, northern Minas Gerais. Each plot consisted of four 5 m long rows, being the useful area of the parcel represented by the two central rows, discarding 0.5 m from each end of the rows. The experimental design was in randomized blocks, in a 2 x 10 factorial scheme. The treatments were a combination of two spacings between sorghum row (0.50 and 10.70 m) and ten weed-crop control or coexistence periods (0, 7, 14, 21, 28, 35, 42, 49, 56 and 120 days after emergence (DAE)), in which for the control periods, the crop was kept weed-free until the established period, and for the coexistence periods the crop was kept in the presence of weeds until the same established period, being kept weed-free until harvest. A phytosociological survey was conducted in the third crop growth stage (EC3), using the inventory square method. The PBI was 19 and 24 DAE for spacing 0.5 m and 0.7 m, Respectively. The TPWI for total fresh matter productivity was 17 and 10 DAE for of 0.5 m and 0.7 m spacings, respectively. There was no TPWI for the other evaluated characteristics. There was no CPWI for any of the evaluated characteristics (PBI > TPWI). The weed species with the highest importance value index (IVI) were Panicum maximum ( 110.93 ), Commelina benghalensis (64.8), Ipomoea cairica ( 46.89 ) and Parapiptadenia rigida (27.7).