SnapPlus Pastures are identified by method of stocking and by animal density:
•Pasture rotational stocking: Rotational grazing with a maximum of 10 days on before rest, with less than 2 animal units per acre during grazing season and 3 inches or greater average minimum grass height.
•Pasture, variable stocking, managed continuous: This represents a system that may have different numbers of animals at different times, but is still managed to provide nutrition for the animals and maintain 3 inches or greater average minimum grass height. Should have less than 2 animal units per acre during grazing season.
•Pasture continuous stocking, low density: Animal may be present continuously, but the density is so low that an average minimum grass height of 3 inches is maintained. No more than 1 animal unit per acre planned during grazing season.
•Pasture continuous stocking, high density: Animals are present continuously or for long periods of time at a high enough density that an average minimum grass height of 3 inches is not maintained and bare areas are present. Greater than 1 animal unit per acre continuous stocking can lead to insufficient surface cover.
•Pasture, dry lot, exercise area: High animal density. Provides <10% nutrition for animals and has many bare areas (50%) throughout growing season. Any area with 10 or more animal units per acre during the growing season should definitely be called a dry lot.
Note: that “grass hay” is not a grazed crop, and therefore does not have the sod disturbance expected with grazing. The SnapPlus grass hay crop assumes three cuttings per year of hay, but there is no disruption of the soil surface when the hay is cut. Therefore, the estimated soil loss from grass hay typically is much less than that from any of the pasture crops.
Also note that SnapPlus soil loss calculations cannot presently account for the soil disturbance caused by gleaning when animals are released on cropland after harvest. SnapPlus can however account for the nutrients applied by gleaning animals using the Grazing Nutrient Rate Calculator.
Recent research has led to improvements in the way RUSLE2 handles grazing and perennial forage crops; a new version with these improvements has been completed and is expected to be released in 2015. We expect that these improvements will allow SnapPlus to better take into account grazing animal density in its RUSLE2 soil loss calculations.