Características de pastos de milheto ou capim sudão sobressemeados na cultura da soja

Abstract

The objective was to evaluate pearl millet and sudangrass, single or mixed with ryegrass, implanted by overseeding in the soybean crop or by no-tillage after harvesting the grains. The experiment took place in 2019 and 2020 in a randomized block design with a 4x2 factorial scheme, with four replications. Eight treatments were used: 4 different pastures (single sudangrass, sudangrass mixed with ryegrass, single pearl millet, pearl millet mixed with ryegrass) in 2 seasons / implantation methods (overseeding in the soybean crop in stage R6 or sowing by no-tillage after soybean harvest). Plant stand evaluation was performed at 10, 20 and 30 days after sowing. The pasture was managed by making cuts when it reached 60 cm, with defoliation intensity of 50%. Before the cuts, the pastures were evaluated: forage mass, heights, lodging index, forage density, tiller population density, and morphological composition. With the forage mass data, total forage production, the daily and monthly forage accumulation rate (forage production dynamics) were obtained. The period of use of the pastures was considered the interval between the first and the last cut of each treatment. The results were compared using the Tukey test (α = 0.05). Interaction (P<0.05) was verified between agricultural year and sowing time for plant height, plant stand, tiller population density, pasture utilization time, total forage production, plant lodging and material proportion dead. These variables were higher (P<0.05) for the pastures overseeded in R6 in 2019, with the exception of the plant stand, tiller density and plant lodging, with no difference in 2020 between sowing times. The pasture utilization time was higher (P<0.05) in the overseeded pastures in both agricultural years. There was no interaction (P<0.05) between seasons and types of pasture for the plant stand, tiller density and morphological separation. The plant stand was higher (P<0.05) for single pearl millet, while tiller density was higher for single sudangrass. The proportion of leaves was higher (P<0.05) in single crops, that of stalks in pastures of single sudangrass, and that of dead material was higher in pastures of sudangrass, regardless of whether in single cultivation or mixed with ryegrass. There was a significant interaction between months and sowing times for the rate of monthly forage accumulation, with greater (P<0.05) accumulation for the overhanging pastures, and greater accumulation in the months of March and April. The overseeding of pearl millet or sudangrass over the soybean crop makes it possible to anticipate the use of pastures, increasing the time of use of pastures and the production of forage.