Interference of increasing densities of sourgrass in grain sorghum

Sourgrass has a high competitive potential, resulting in yield losses of several crops. With the growth of grain sorghum cultivation in the Cerrado , mainly in the second crop, studies are needed to assess the interference of sourgrass on this crop. The objective of this work was to evaluate the interference of increasing densities of sourgrass on the sorghum crop under Cerrado conditions. The field experiment was carried out in a randomized block design with four replications. Five treatments, composed of densities of 0, 2, 4, 6, and 8 sourgrass plants per m 2 , were evaluated. To simulate the densities of sourgrass, this species was planted in the predecessor crop (soybean) according to the predicted density in each experimental unit, and later, at the time of sowing the sorghum, the sourgrass plants, which were clogged, were cut, in order to simulate the condition provided by mechanized harvesting. During the evaluation of the effect of the treatments on the sorghum crop, the stand and plant height, stalk diameter, panicle length, mass of 100 grains, and yield were measured. The increase in sourgrass density in coexistence with sorghum negatively affects all vegetative and reproductive parameters evaluated in the crop. For each sourgrass plant m -2 in coexistence with sorghum, there was a reduction in yield equivalent to 445 kg ha -1 . The maximum reduction in sorghum yield observed was 87%, in a condition in which the crop was developed in coexistence at the density of 8 sourgrass plants m -2 .