Abstract
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 .
Highlights
Resumo – O capim-amargoso apresenta elevado potencial competitivo, proporcionando perdas no rendimento de diversas culturas
Sourgrass is widespread in practically all of the Brazilian territory (Ovejero et al, 2017), infesting cultivations of the most varied crops, including grain sorghum exploited under second crop conditions
A reduction of one sorghum plant per linear meter was observed when the crop was subjected to coexistence with a density of approximately 1.47 sourgrass plants per m2
Summary
Resumo – O capim-amargoso apresenta elevado potencial competitivo, proporcionando perdas no rendimento de diversas culturas. The production of sorghum in Brazil has grown annually, especially when considering the commercial exploitation of this crop under second crop conditions (known as “safrinha” in Brazil) (CONAB, 2021). This fact can be partially attributed to its greater tolerance to high temperatures and water deficit compared to corn crop. Due to the intense use of glyphosate in agriculture, and the consequent high selection pressure, reports of glyphosateresistant weeds have been increasing worldwide (Heap, 2021) Among these reports, the existence of sourgrass (Digitaria insularis) biotypes resistant to glyphosate and ACCase inhibitors stands out in Brazil. Sourgrass is widespread in practically all of the Brazilian territory (Ovejero et al, 2017), infesting cultivations of the most varied crops, including grain sorghum exploited under second crop conditions
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