Contamination of freshwater systems by nutrients has been studied extensively in the eastern U.S. Little research on the fate of nutrients in grazing conditions has been done in the western U.S. Western agriculture is often irrigated and research addressing the potential for leaching under these conditions is warranted. This study used Management Intensive Grazing (MIG) and eight grass-legume mixtures to evaluate the management and forage choice in relation to nitrogen and phosphorus leaching to ground water. Soil water samples were taken weekly through the growing season from 2001 through 2003. Water samples were analyzed for nitrate, ammonia, and phosphate. Soils were described and a textural discontinuity was discovered in two of the six soil profiles described. Data were analyzed by treatment, grass, legume, and soils by treatment. Three-year nitrate-N means were found to be in a range of 4.50 to 48.10 and 2.11 to 49.5 mg NO3 - -N L-1, at 60 cm and 90 cm, respectively. The amount of leaching depended on the grass-legume mixture as well as the soil characteristics. Significant differences were found between grasses (P=0.0001) with tall fescue leaching the least and orchardgrass leaching the most. Differences in leaching under legumes were also found to be significant (P=0.001), with white clover always leaching more than birdsfoot trefoil when significant differences were observed. Ammonia leaching was nonsignificant at a studywide analysis. Phosphorus treatment concentrations ranged from 0.025 to 0.41 mg PO4- -P L-1 and were significantly different (P=0.001). A comparison by grass type indicated that perennial ryegrass leached significantly higher concentrations of P (P=0.01) at 60 cm than the other grasses, but found no difference at 90 cm. No significant differences were found between legumes at either depth. Leaching of P was less affected by the soil textural discontinuity than nitrogen leaching. Soil differences affect leaching in varying degrees. Nitrate was affected most strongly by soil differences. These differences were more strongly evident at 60 cm than 90 cm. Soils affected phosphorus leaching differently than nitrate, and were more strongly affected at 90 cm than at 60 cm. Ammonia was not affected by soil characteristics.

Virginia dairy producers are considering intensive grazing as a profitable and ecologically viable alternative to confinement dairy production. The objective of this study is to compare financial performance for pasture-based dairy farms relative to similar resourced-based confinement farms. Comparisons are based on the recommended financial and profitability measures of performance provided by the Farm Financial Standards Council. Primary and secondary data plus simulation of daily pasture supply and animal demands are used to develop 100 and 200-cow farms with a land base representative of the Ridge and Valley regions of Virginia. Representative farms were developed to explore financial performance based on the intensity of pasture use, from total confinement to seasonal farms using intensive grazing (in which pasture, hay, and energy supplements are the only sources of nutrients for all dairy animals on the farm). Results of the analysis demonstrate that pasture-based seasonal production is more profitable and has a higher level of repayment capacity and financial efficiency than all other production systems in this study. Greater financial performance by the seasonal farms is obtained even though such farms obtain lower average annual milk prices and 10 percent less milk sold per cow than the similar confinement farms. Pasture-based farms that feed a partial total mixed ration during the summer (25 percent of ration dry matter and 45 percent of ration dry matter from pasture) have fewer financial advantages than the seasonal farms. However, their performance exceeds that of the confinement farms and intensive pasture-based farms milking year round. The intensive pasture-based farms milking year round are the poorest financial performers. Additional conclusions for this study are: 1) the 100-cow farms exhibit insufficient financial performance to provide for family living, debt service (at 40 percent debt to equity ratio), and a cushion for events such as droughts or declines in milk prices; and 2) financial performance of the 200-cow dairies is better, yet the added income from a member of the farm having off-farm income will provide a cushion against unforeseen production and financial risks. Follow up research should address the interface of three issues; stocking rates, farm profitability, and environmental compliance. / Ph. D.

Dairy producers across the country are evaluating the effectiveness of management intensive grazing (MIG) systems as a means of reducing the economic pressures of confinement feeding and manure handling. Systems using MIG have been promoted as an environmentally safer way of managing nutrient balance on Center. However, little research has been conducted to evaluate how these systems affect phosphorus (P) loss from the Center through runoff and forage removal. The goal of this study was to investigate the effects of forage type and manure density on P levels in runoff from release plots that simulated a MIG dairy system. Two forage treatments were planted on runoff release plots and applied with three manure density treatments and four replications of each combination for a total of 24 plots. Orchardgrass (Dactylis glomerata) and a broad-leafed forage treatment consisting of buckhorn plantain (Plantago lanceolata), red clover (Trifolium pratense), and alfalfa (Medicago sativa) were planted on the runoff release plots in early spring. Manure densities with no manure (control), a density simulating a low stocking density (low), and a density simulating high stocking density (high) were applied to plots during grazing simulations. Six rainfall simulations were conducted over the season simulating grazing conditions when forage was removed and re-growth conditions when forage had reached its target re-growth height before re-grazing occurred. Thirty minutes of runoff was collected from the runoff release plots to determine first flush phosphorus losses from the various treatments. Mass losses of total phosphorus (TP) for manure treatments in series 1 were significant due to plot installation disturbance. No significant effect for ortho-phosphorus (ortho-P), particulate phosphorus (PP) or TP concentration or mass losses were observed for other simulation series. Significantly higher mass losses were observed in series 1 for both forage treatments, again due to installation disturbance. Seasonal mass losses for TP were significantly lower for the orchardgrass treatment. Forage mass removal over the season increased as the stands established. Orchardgrass treatments appeared to control P losses earlier in the season, while broadleaf treatments observed a steady increase in ortho-P losses up to series 5. Both mass and concentration losses of TP were controlled earlier in the season by orchardgrass, while PP showed no significant mass or concentration loss effects. / Master of Science