Date of Graduation
Eberly College of Arts and Sciences
Eugenia M. Pena-Yewtukhiw
With growing human populations, we need to produce more food. Food production requires growing crops and raising livestock with existing and suitable land resources, potentially causing nutrient (phosphorus (P) and nitrogen (N)) pollution. For purposes of this study, the runoff potential for the mixed and single species grassland grazing will be examined. Mixed species grazing refers to cattle and sheep grazing concurrently in the same area; while single species grazing refers to cattle grazing alone. Understanding the environmental effects of mixed grazing as compared to a single species grazing systems will help to improve farming and agricultural practices that increase sustainability and protect the environment. The goals of this study were to demonstrate how to select land management practices to maximize production while increasing environmental and farm sustainability; and to determine a direct relationship between land degradation and the two different types of grazing systems. The specific objectives of this study were to measure the effect of animal activity by monitoring selected soil characteristics/properties; and to characterize the soil properties that could be affecting water erosion and P movement in runoff water. The main hypothesis was that the single species grazing system would generate higher environmental impact (negative impact on physical and hydrologic soil properties) than the mixed species grazing system. Two experiments were developed at the WVU Animal Research farm to answer the objectives of the study. Three fields divided into six 1-ha plots were subjected to either mixed or single species grazing treatments. Two erosion plots were installed per treatment, resulting in a total of 12 erosion plots. Stratified soil samples were collected in a 10m x 10m grid pattern, as well as within 30 cm of the erosion plots, on three separate sampling dates: August 2011, April 2012, and August 2012. Runoff and sediments from erosion plots were collected after every significant rain event. The measured soil properties were bulk density, penetration resistance, aggregate stability, nutrient content, pH, organic matter content, and infiltration rate. A block ANOVA statistical analysis of the data found no statistically significant difference in bulk density between treatments; however, a significant (P = 0.1) difference was observed in bulk density between sampling dates. Bulk density was significantly lower after winter grazing in April 2012 (0.98 +/- 0.10 g/cm3 ) than after spring grazing in August 2011 and August 2012 (1.03 +/- 0.09, 1.09 +/- 0.08 g/cm3, respectively). Penetration resistance was consistently higher at every depth in the single species grazing system than in the mixed species grazing system; however, this difference was not statistically significant. In general, the mixed grazing system exhibited larger dry and wet aggregate stability than the single species grazing system, however the results were not statistically significant. Overall pH was slightly acidic for the study area (5.15 +/- 0.45), which could inhibit the bioavailable nutrients; however, this effect of pH on the bioavailable nutrients was not observed with this study. The overall phosphorus content for the study area was 104.7 +/- 51.6 mg/kg, which was well above the reported optimum P content for established mixed grasses (Penn State, 2012). Overall, the single species grazing exhibited higher P than in the mixed species treatment. Potassium followed the same trend in that the overall K content for the study area was 320.8 +/- 158.6 mg/kg; which is on the higher end of the recommended K contents for established mixed grasses (Penn State, 2012). Potassium also followed the same trend as P in that the single species grazing exhibited larger bioavailable K contents than the mixed species grazing system. Other studies have found that an increased K content at the surface increases the risk for K to be transported with sediments. The overall SOM (0-5 cm) content of the experimental area was 90.0 +/- 20.2 g/kg. The single species grazing treatment exhibited an overall average surface (0-5 cm) SOM of 91.7 +/- 17.7 g/kg, a value that was higher than that measured for the mixed species grazing treatment (88.2 +/- 22.7 g/kg); the measured difference between grazing treatments was not statistically significant. Overall, the mixed species grazing treatment exhibited a faster infiltration rate than the single species grazing treatment. The average runoff volumes were separated into three periods. Average runoff volume for the mixed species was greater than the single species treatment at two of the three Periods; however the single species produced more sediment than the mixed species treatment at two of the three Periods. A split-plot ANOVA determined these differences were not significant. The average runoff volumes for the two treatments do not support the hypothesis of the study; however, all other measured variables depict trends that indicate that the single species grazing system generates a higher environmental impact than the mixed species grazing system. Since this study was only established in 2009, more research may need to be implemented to see more significant effects of the grazing treatments.
Parks, Brittany, "Grazing impacts on sediment production and runoff from single and mixed species grazing" (2013). Graduate Theses, Dissertations, and Problem Reports. 387.