Influence of Season of Grazing and Intensity of Grazing on Vegetative Composition and Yields

Abstract

Mixed prairie range sites vary in ability to produce for age for livestock consumption. One reason for the difference in variation is the degree of utilization of the ranges in past years. The purpose of the study was to determine variation in composition, cover and yields of grasses due to different intensities of grazing and season of use on two break range sites in the central Mixed Prairie. Four pastures were selected for study: a moderately summer-grazed, moderately year-long grazed, heavily winter-grazed, and heavily over-grazed summer and fall. All areas were compared to the cover, composition and yields of forbs and grasses on a nearby non-grazed area. Study areas were about the same size, well-watered and in a one-square-mile area. An accurate fifteen-year history on season of grazing and the number of cattle on each area except the heavily overgrazed pasture was available. On the basis of vigor illustrated by the decreaser forb, lead plant, the heavily grazed winter pasture supports a more vigorous type of plant life than any other area studied. The non-grazed area had the highest composition of climax species, such as big bluestem, little bluestem, side-oats grama, switch grass, and Indian grass. The heavily winter grazed pasture had a composition of climax species similar to that of the non-grazed area. But, as the intensity of grazing increased (with the exception of the heavily winter grazed pasture) composition of climax species decreased. Statistical comparisons of composition of big bluestem, little bluestem and side-oats grama showed no significant difference between the non-grazed area and the heavily winter-grazed pasture on the deep break site. However, when composition of the three grasses on the non-grazed area was compared to that of the moderately year-round grazed pasture and the heavily overgrazed pasture there was a significant decrease in the grasses with grazing at the 99 percent confidence limits. The density of forbs per square foot, and total number of species generally increased with increased grazing intensity. The number of plants generally increased as the grazing intensity increased. In general, forage production was greater in the heavily winter-grazed pasture than all others. When intensity of grazing increased on both deep and shallow break sites, total yield of forbs was higher (except on the heavily winter grazed pasture) and the total yield of mulch was lower