Temperate Grass Response to Frequency and Extent of Grazing.

Grazing management has a significant impact on pasture growth.  Our objective was to determine the influence of grazing frequency and extent of defoliation on seasonal yield distribution, forage nutritive value, and persistence of temperate perennial grasses.  Meadow fescue [Schedonorus pratensis (Huds.) P. Beauv.], orchardgrass (Dactylis glomerata L.), quackgrass [Elymus repens (L.) Gould], and reed canarygrass (Phalaris arundinacea L.) were rotationally grazed at a vegetative (3- to 4-leaf stage or 25 cm tall) or mature (boot stage or 50 cm tall) stage to remove 50, 75, or 100% of the herbage on a height basis.  When grasses were grazed at a vegetative stage, increasing the extent of defoliation decreased the number of grazing events from six to four year^-1, increased annual dry matter (DM) yield (3850, 5050, and 4980 kg DM ha^-1, respectively), had no effect on forage nutritive value, and decreased tiller density 15% by the end of the season.  When grasses were grazed at a mature stage, increasing the extent of defoliation increased annual yield (4300, 4870, and 5300 kg ha^-1, respectively), decreased forage nutritive value, particularly in the spring, and decreased tiller density 20% by the end of the season.  Grasses that were subject to 50% defoliation at vegetative stage were ready to be grazed the following spring two weeks earlier than those subjected to 100% defoliation.  The results suggest that while short-term annual productivity is increased, growth rate and persistence of temperate grasses is negatively associated with residual sward height regardless of maturity.