The aim of this study was to determine the yield variation patterns in orchard grass (Dactylis glomerata L.) under grazing management. This study was performed in Montecillo, Texcoco state, Mexico from June 2005 to July 2006. Three grazing frequencies (21, 28 and 35 days) and two grazing intensities (5-7 and 9-11 cm residual sward high) were evaluated in a completely random block design with three replicates. The variables grass yield, seasonal distribution, growth rate, botanical and morphological composition and tiller population density were all evaluated. A 35 day-grazing frequency produced the highest yield (P<0.05). Independently of the grazing intensity and its frequency the seasonal yield was: 49.5, 31.6, 14.1 and 4.8% for spring, summer, winter and fall, respectively. The highest growth rate was registered during spring when grazing occurred every 35 days, and the lowest during autumn when grazing occurred every 28 days (P<0.01). During winter grazing only occurred every 21 days, and this may have led to 60% contribution to total yield by other species. Results also suggest that tiller density was not affected by grazing intensity and frequency on tiller population density.

Keywords: grazing management, grass yield, seasonal distribution