Long-Term Ecological Grazing Intensity Research in the Missouri Coteau of North Dakota

Soil Water and Forage Production


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 overflow range 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 silty range 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 10 years of the study. On silty range 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 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 silty sites forbs are highest in neutral detergent fiber on the ungrazed and extreme grazing treatments. As the ungrazed forage matures on the ungrazed treatment it becomes higher in fiber. On the heavily grazed treatments, only forbs of lower quality would remain ungrazed. These differences in nutritional quality have occurred gradually over the course of the study.


 

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