The Colombian Altillanura is a microregion that typifies a extensive cattle production system which requires the use of adapted grasses responding to nitrogen fertilization to improve yield and nutritional quality grassland to intensify livestock production systems. The study was conducted at the headquarters Taluma CORPOICA, located at 04 ° 34'25 "west and 71 ° 20'10" north in the town of Puerto López - Meta, under conditions of climate and soil of the Colombian Altillanura. The objective of

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... is study was to determine the agronomic and nutritional behavior of genotypes of Brachiaria brizantha CIAT 16315, 16467, 26990, 26124, 6387 and Mulato II, handled single nitrogen fertilization and associated with the legume Pueraria phaseoloides. Design of randomized complete block arrangement in divided stripes, where the plot corresponded to the forage grass strip and the level of nitrogen fertilization was used (N46, N92, and N46 + P. phaseoloides). Accessions with greater biomass production (p<0.001) were B. brizantha CIAT 16315 (2040 kgDM.ha-1), B. brizantha CIAT 6387 (2033 kgDM.ha-1) and B. brizantha CIAT 16467 (1864 kgDM. ha-1). Treatment grasses + N92 values had significantly (p<0.001) higher in CP (9.55%) and degradability of forage (65.7%) and lower dry matter content (37.05 %%), NDF (61.97%) and FDA (30.55%) compared with the response of grasses fertilized with 46 kgN.ha-1 and grasses associated with kudzu and fertilized with 46 kgN.ha-1. For higher CP content (p <0.001), materials B. brizantha CIAT 16315 (8.34%) and CIAT 26124 (8.06%) which did not differ significantly with grazing Mulato II (8.18%). The results demonstrated the importance of nitrogen fertilization on the production and nutritional quality pastures B. brizantha.