Drought and grazing: II. Effects on runoff and water quality
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Authors: W. E. Emmerich, and R. K. Heitschmidt
Date: 2002
Journal: Journal of Range Management
Volume: 55
Number: 3
Pages: 229-234
Summary of Methods: The effects of grazing and drought on runoff, erosion, and nutrient transport were measured over three years with 12, 50 m2 lysimeters on native grassland near Miles City, Montana on the Fort Keogh Livestock and Range Research Laboratory (46° 22’ N; 10° 5’ W). Five treatments combinations, testing 2 precipitation levels (drought-reduction of growing season precipitation by 80% during second year of the study, non-drought) and 3 levels of grazing (rest-no grazing, grazing during drought only, grazing during and after drought) were applied. Drought treatments were applied during the second year of the study. Six ewes and their twin lambs grazed for one day in early June and early July to achieve moderate use levels (40-50% utilization). Soil chemical and physical properties were measured at the beginning of the study. Storm runoff was measured at each site from the first of May to the end of October with runoff and sediment samples collected from each runoff event.
Article Summary / Main Points: Runoff, sediment load and nutrient transport were not affected by drought, though there was a trend for increased runoff and sediment yield the year following the drought. In the third year, grazing increased runoff and sediment yield and decreased water quality compared to no grazing. The combination of drought and grazing tended to increase runoff and sediment yield. The increases in runoff, erosion, and nutrient transport were concluded to be minimal when compared to natural site variability.
Vegetation Types: Riparian and Wetlands
MLRA Ecoregions: 58A Northern Rolling High Plains, Northern Part
Agrovoc Control Words: Runoff water Rangelands Drought
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: erosion, sediment yield, nutrient transport, great plains, lysimeter, nitrogen, phosphorus, nutrient yield
Annotation: The absence of runoff from the drought-treatment lysimeters, due to below-normal precipitation the year precipitation treatments were applied, prevented a direct assessment of drought and grazing interactions. This limits the wide spread application of this experiment.
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