The Impact of Mixed and Single-Species Grazing On Soil Hydraulic Properties and Selected Grassland Characteristics.

Grasslands support their own unique plant and animal species. Vegetation helps to prevent erosion by providing cover to protect the soil surface from raindrop impact, and by increasing root mass to hold surface aggregates together; animal grazing behavior will directly affect vegetation and soil cover. Understanding the environmental effects of mixed grazing as compared to a single species grazing system will help to refine our farming and agricultural practices with the purpose of increasing sustainability and protecting the environment. The objective of this study is to characterize soil hydrologic properties as affected by single and mixed species grazing systems. To achieve the study’s objective a completely randomized factorial experiment composed of one factor (grazing system) with two treatments, and three replicates was established at WVU Reedsville Animal Research Farm. To assess the environmental impact of the two grazing systems on soil hydraulic properties, infiltration rate, bulk density, soil texture, soil structure, and runoff volumes were collected. To test the runoff, infiltration, and sedimentation, erosion/infiltration plots were installed in each replicate in May 2011. Soil surface samples were taken to determine the remaining soil properties mentioned above. It has been observed in previous years the differences in animal species affect the vegetative cover remaining after they have moved out of the paddocks. It was determined that runoff volumes were statistically significantly different between the two grazing systems. The mixed species grazing system exhibited higher average runoff volumes ranging from 3222 mL to 5346 mL, while the single species grazing system produced average runoff volumes ranging from 896 mL to 2113 mL (for the same rain events). Surface saturated hydraulic conductivity was highly variable, ranging from 30 mm/hr to 284 mm/hr. Surface bulk density showed low variability with a range from 0.88 g/cm³ to 1.13 g/cm³. Low bulk density indicates a high pore volume. Correlation analysis show, that average runoff and the aggregate geometric mean diameter are statistically significant (α = 0.05) and negatively correlated. The relationship suggests that presence of large aggregates decrease the average amount of runoff. The data suggest that the mixed species grazing system affects soil surface properties and soil cover, and as a consequence more runoff is produced in this system than the single species grazing system. The data suggest that, over time, land management practices can affect the sustainability of the grassland based on soil and grassland hydrologic properties.