Mixed production of Alexandergrass and sorghum under nitrogen fertilization and grazing intensities

Abstract

Annual pasture specie are used in southern Brazil to supply forage in the fall and spring when major forage species have their productivity diminished. Forage sorghum (Sorghum bicolor, (L.) Moench) is a suitable option that has been adopted by farmers due to its high quality as forage. It has been observed that in areas where forage sorghum is cultivated, alexandergrass (Urochloa plantaginea) usually appear as a spontaneous specie. The aim of this study was to observe the effect of two grazing intensities (30 and 60 cm of sward height) and two nitrogen fertilization levels (0 and 200 kg N ha-1) on the quantity (forage mass), quality (CP, ADF, NDF, Lignin, Hemicellulose, Cellulose) and morphological components (stem, leaves, senesced material) of sorghum-alexandergrass mixed pasture grazed by beef cattle. Treatments were arranged in a completed randomized block design with three replications in a 2 x 2 factorial scheme. Forage mass was increased during the evaluation period. In the first period, production was 4,022 kg and it reached 5,233kg DM ha-1 in the third period. Treatments did not affect AG-sorghum mixed pasture botanical profile or quality. It was observed that Sorghum lowered its contribution from 63.4% in the first evaluation period to 21.5% in the third. In contrast, Alexandregrass (AG), contribution increased from 17.9 to 52.7% throughout the evaluation periods. Therefore, the addition of Alexandergrass to a planted sorghum pasture is encouraged because it can extend the grazing period into the fall by prolonging the pasture favorable sward structure and nutritive value.