Agronomic performance of sorghum as a response to 2,4-D application dosage and timesSorghum is part of the current plan of agricultural system management for the cer rado. However, few field studies have been carried out on this culture's behavior and selectivity towards herbicide 2,4 D. The objective of this study was to evaluate the effects of 2,4-D on plant growth, dry matter production and green biomass and grain yield in sorghum. The experiment was conducted between January and May 2008 in Nova Xavantina-MT in dystrophic Oxisol. Sorghum (cv. Buster) was sown in a cultivated area under no-tillage, with 0.50 m spacing between rows, and ten seeds distributed per meter. Treatments were arranged in a 4 x 4, involving four levels of 2,4-D (0, 335, 670, and 1.005 g ha -1 ) and four application times (pre-sowing, three fully-expanded leaves, six leaves, and pre-flowering).A randomized block design was used, with four replica tions. Weed control in the culture was performed manually, using a hoe. Toxic effects caused to sorghum by 2,4-D were observed at 15 days after application (DAA), regardless of dose or time of application. The increasing levels of 2,4-D caused a linear reduction in plant height, biomass and green dry matter accumulation, both at 30 DAA as the point of rollover. The application of 2,4-D affected sorghum yield, especially at doses above 1.005 g ha -1 and late applications. In general, the use of 2,4-D in pre-sowing proved to be a good alternative for the management of weeds in sorghum crop.
synthetic auxins; Sorghum bicolor; selectivity; productivity; growth
