85 AJCS 14(01):85-91 (2020) ISSN:1835-2707 doi: 10.21475/ajcs.20.14.01.p1891 Mixed production of Alexandergrass and sorghum under nitrogen fertilization and grazing intensities André Brugnara Soares* 1 , Marcieli Maccari 2 , Carine Lisete Glienke 3 , Tangriani Simioni Assmann 1 , Marcos Antonio de Bortolli 1 , Denise Adelaide Gomes Elejalde 1 , Regis Luis Missio 1 1 Technological Federal University of Paraná (UTFPR), Brazil 2 West Santa Catarina University (UNOESC), Brazil 3 Federal University of Santa Catarina (UFSC), Brazil *Corresponding author: soares@utfpr.edu.br 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. Keywords: Botanical composition; Structural composition; Sorghum bicolor; Urochloa plantaginea. Abbreviations: ADF_acid detergent fiber; AG_Alexandregrass; CP_crude protein; DM_dry matter; NDF_neutral detergent fiber. Introduction Annual pasture species are used in high-input intensive grazing management systems in southern Brazil. On top of their high forage quality, they supply biomass in the fall and spring when major forage species have their productivity are diminished. Forage production and accumulation is affected by genetic, soil and climate factors (i.e. temperature, photoperiod, water availability and nutrients). Among the macronutrients, nitrogen is highlighted due to its presence on proteins, enzymes, phytocromes, coenzymes, nucleic acids (DNA and RNA), nitrogenous basis as well on chlorophyll and phytohormones. Forage sorghum (Sorghum bicolor, (L.) Moench.) is a suitable option that has been adopted by farmers due to its high forage production potential, high nutritive value and drought tolerance. It has been observed that in areas where forage sorghum is cultivated, volunteer Alexandergrass (AG) (Urochloa plantaginea) is common, as it is on row crops nearby (mainly corn and soybeans). Alexandergrass is considered and managed similar to a weed, not only on row crops but also on forage fields. However, its excellent tillering and forage accumulation characteristics (Martins et al., 2000; Restle et al., 2002; Sartor et al., 2011; Costa et al., 2011; Menezes et al., 2014; Mezzalira et al., 2014) suggest that managing volunteer Alexandergrass as a forage species can be a viable alternative. Recent research (Oliveira et al., 2018) supports the practice by generating guidelines for Alexandergrass management through herbicide application. Using volunteer AG on cultivated sorghum fields in integrated crop-livestock systems can be a viable low-cost alternative and it will allow longer pasture period of utilization. Annual grasses has a short cycle of utilization characterized by fast structural changes of high magnitude, while a spontaneous grass like AG has a more longer period of utilization because its growth patterns are different. Nitrogen fertilization and sward height management influence forage accumulation and nutrient usage efficiency. Due to heterogeneity in grazed swards its structure is changed along time. Sward structure impacts animal movement and