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

Forage Production and Utilization Treatment Effects

The first year in which the amount of forage produced under the various grazing treatments was significantly different was 1992 on silty range sites and 1993 on overflow range sites. Table 6 gives the average forage production by treatment on silty range sites at the beginning of the grazing season, mid-season, peak of the season, and end of the season for the period from 1992 to 2005. Table 7 gives the same information for overflow range sites averaged over the period from 1993 to 2005. For both range sites the extreme grazing treatment produces the least forage. However the ungrazed treatment is not the most productive. The light treatment is the most productive on silty range sites. There is little difference between light, moderate and heavy treatments on overflow range sites but moderate tends to be the most productive. There is no year X treatment interaction between treatments on overflow range sites. That means the effect of grazing intensity on forage production is consistent across all of these years. However there is year X treatment interaction on silty range sites. This indicates that the weather for the year, or the previous year, may affect which grazing treatment produces the most forage. At the beginning of the grazing season the most productive site varied between the ungrazed, light and moderate treatments with the extreme or heavy always being least productive. At the middle of the season and in peak yield, the light treatment produced the most forage or at least was not significantly different from the most productive treatment and the extreme produced the least forage or was not significantly different from the least productive treatment. At the end of the season the light or moderate was most productive and the extreme or heavy was least productive although ungrazed produced the least in 1994 and the mean for ungrazed was greater than light in 2002. Although there were no significant differences 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 that 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 silty range sites and production decreased as grazing intensity increased. Annual rainfall in 1993 was the second highest of any year during this study and the greatest forage production on silty range sites occurred during that year (see Table 2). The buildup of litter in that year may have been the factor that caused the ungrazed treatment to be the least productive treatment in 1994.

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