At the Centro Nacional de Investigacion, located in Palmira (Colombia) a trial was conducted to study the irrigation-fertilization interation in forage pasture in a vertisol (Typic pellustert). The experimental design was carried out as sub- subdivided plots with three repetitions: giving a 3 x 3 x 3 factorial arregement (the study var cables were irrigation, fertilization and forage specie). And additional treatments, consisting of the respective species with no irrigation and no fertilization, were included. Water management treatments were selected from K=Et/Ev as: Et=evapotranspiration, Ev=evaporation in the class A tank. Nitrogen fertilization treatments were made by the broadcast of 50, 100 and 150 kg/ha. Some of the results indicated that green forage yields in t/ha to irrigation and fertilization as: H-534 K=0.8 and 75 kg/ha; King grass K=0.8 and 100 kg/ha; Naiper Enano K=0.8 and 100 kg/ha.