Prior to 1992, the amount of forage produced under the different grazing treatments was not significantly different. Starting that year, forage production under the various grazing treatments differed significantly on the loamy ecological sites. During 1993, the same was true on loamy overflow ecological sites. Tables 7 and 8 list the average forage production by treatment. For both types of ecological sites, the extreme grazing treatment produces the least forage. On the other hand, the ungrazed treatment is not the most productive. On loamy ecological sites, the light treatment has the highest production. On loamy overflow ecological sites, the light, moderate, and heavy treatments show little difference, but the light grazing treatment tends to be the most productive.

Year X treatment interactions have been found only at the beginning of the grazing season for both ecological sites. The weather for the year, or from the previous year, can affect which grazing treatment produces the most forage. On loamy overflow ecological sites the most productive treatment at the beginning of the season varied between light, moderate and heavy in different years. On loamy ecological sites at the beginning of the grazing season, the most productive site varied between the ungrazed, light, and moderate treatments, with the extreme or heavy treatments always proving to be least productive.

Although there were no significant differences between treatments in biomass production in 1991, the fact that there were differences at the beginning of the 1992 grazing season indicates that grazing must have reduced the amount of carbohydrate reserves the plants were able to carry over to the next season. Part of the variability in production on the ungrazed treatment may be the result of litter buildup that can prevent rainfall and sunlight from reaching the ground. In 1992 and 1993, the ungrazed treatment produced the most forage on loamy ecological sites and production decreased as grazing intensity increased. Annual rainfall in 1993 was the third highest of any year during the study and the third greatest forage production on loamy ecological sites occurred during that year (see Table 2). The buildup of litter in that year may have caused the ungrazed treatment to be the least productive treatment in 1994.

Soil Water

Soil water has been sampled bi-monthly throughout the growing season on each of the vegetation monitoring sites, and differences in available water have developed between the different grazing treatments. On loamy overflow ecological sites, lightly grazed pastures have more available water than heavily grazed pastures. The differences in available water occur during both soil water recharge and discharge. This indicates that on heavily grazed sites, more water runs off during a rain, and sunlight evaporates more water from the soil surface. On loamy ecological sites, moderately grazed pastures have more available water than ungrazed or heavily grazed pastures. The ungrazed treatment has less available water because the plants on that treatment have more leaf area than the grazed plants, and more water is removed from the soil by transpiration. 

Forage Quality

The nutritional quality of the forage was sampled at the middle of the grazing season each year for the first ten years of the study. On loamy ecological sites, the grasses have higher crude protein and digestibility and lower fiber components at the higher grazing intensities. On the heavily grazed treatments, the grass that is available for grazing is mostly regrowth, which is of higher quality. However, on loamy overflow sites, both grasses and forbs are highest in fiber components on the heavy grazing treatment. Perhaps on these sites cattle are selecting species of higher quality and leaving those that are higher in fiber. On loamy sites, forbs are highest in neutral detergent fiber on the ungrazed and extreme grazing treatments. As the forage matures on the ungrazed treatment, it becomes higher in fiber. On the heavily grazed treatments, only forbs of lower quality remained ungrazed. These differences in nutritional quality have occurred gradually over the course of the study.

Table of Contents

• Introduction
• Stocking Rate
• Livestock Response
• Effect of Grazing Intensity on Forage Production and Utilization, Soil Water and Forage Quality
• Plant Community Dynamics
• Recommendations