Runoff from Pastures in Relation to Grazing Intensity and Soil Compaction
Journal of the American Society of Agronomy , 39 , 1947
Alderfer, R.B., Robinson, R.R.
Runoff losses during the summer from various sites in pastures and grasslands on Hagerstown and Morrison soils were determined by means of a type F rainfall simulator. Water losses were supplemented by measurements of vegetative cover, percentage slope, volume weight, capillary and noncapillary porosity, organic matter content, pH, and the mechanical analysis of the soil. Runoff losses ranged from none to 80% during a x-hour period in which z.4 inches of water were applied. In general, water losses were high from heavily grazed pastures, whereas ungrazed areas lost little if any water due to runoff. The high rate of runoff from the heavily grazed sites was associated with lack of soil cover together with high volume weights and low values for noncapillary and total porosity in the 0 to 1-inch surface soil layer. Compaction was confined to the 0 to 1inch layer even though this layer contained the greatest amount of organic matter. This is indicated by low volume weights and high noncapillary porosity in the 1- to 3- and 3- to 6-inch soil layers. Since storms of high rainfall intensity are common during the summer months, it is suggested that water loss due to runoff may be an additional factor contributing to the low yields of closely grazed pastures during midsummer.