Sourgrass Interference on Soybean Grown in Brazilian Cerrado

Abstract

Sourgrass (Digitaria insularis) is one of the main species causing significant losses in Brazilian soybean production systems. Thus, this paper aimed to evaluate sourgrass interference on soybeans grown under Cerrado conditions. Three field experiments were conducted, of which the first two (E1 and E2) simulated sourgrass after pre-sowing burndown, using plants already emerged by the time soybeans were sown; whereas the third (E3) simulated both sourgrass and soybeans emerged simultaneously. Both E1 and E2 were conducted in a randomized complete block design (RCBD) with five treatments based on sourgrass infestation densities (0, 2, 4, 6, and 8 plants m-2) and four replications. In turn, E3 was also carried out in an RCBD but with treatments arranged in a 2 x 5 factorial and four replications. The first factor comprised two soybean cultivars, while the second was sourgrass density levels, just as in E1 and E2. The results showed that increasing sourgrass densities reduced soybean yield regardless of the plant growth stage when the crop was sown. Yield losses were higher when sourgrass plants were already established by the time soybean was sown. Soybean yield losses reached up to 80% under higher sourgrass infestation levels.

Weed Competition on Soybean Varieties from Different Relative Maturity Groups

“…In contrast, the more significant growth of soybean plants, verified in the evaluation performed at 14 DAE in the treatments weeded after 20 DAE and without weeding, about the treatments weeded throughout the entire cycle and weeded up to 20 DAE, is a result of competition for light. This provoked the etiolation of the plants due to the shading imposed by the weeds, as reported in previous research [9,19].…”

“…Mainly, these yield losses are due to the weed competition for space, water, light and nutrients, besides other effects such as allelopathy and the weeds serving as hosts for pests and diseases [7]. The intensity of weed competition may vary according to the density and composition of weed species present in the agricultural area, as well as the competitive ability of the variety used, soil and crop management practices, and the period of coexistence between the crop and weed community [5,[8][9][10]. Thus, the interference of weeds in the crop can cause reductions of up to 80% in grain yield [9].…”

“…The intensity of weed competition may vary according to the density and composition of weed species present in the agricultural area, as well as the competitive ability of the variety used, soil and crop management practices, and the period of coexistence between the crop and weed community [5,[8][9][10]. Thus, the interference of weeds in the crop can cause reductions of up to 80% in grain yield [9].…”

The population density of Digitaria insularis influences Phaseolus vulgaris agronomic traits

“…Due to huge losses caused to crops and its difficulty of control, sourgrass [Digitaria insularis (L.) Mez ex Ekman] has drawn attention from Brazilian farmers in the last years (Braz et al, 2021;Silveira et al, 2018). Its high persistence in the environment because of rhizome formation and easy dispersion due to its high number of seeds with high germination percentage (Zambão et al, 2020) is aggravated by the glyphosate resistant biotypes (Takano et al, 2018).…”

Regime Hídrico E Palha Influenciam Na Eficácia De Herbicidas Pré-Emergentes No Controle De Capim-Amargoso?

“…Segundo Braz et al (2021), a massa seca da parte aérea da soja diminuiu em resposta ao aumento das densidades de capim amargoso. Sendo que a massa seca da soja diminuiu 55% sobre infestação de 8 plantas de capim amargoso por m 2 .…”