1a. Objectives (from AD-416)
The objectives of our project are to: 1) measure N and P loss in runoff from 8 pastures representing different grazing management strategies over at least 2 years; and 2) use the runoff data to validate the ability of our SurPhos model to predict P loss in runoff from grazed pasture.
1b. Approach (from AD-416)
Runoff plots will be established at the UW-Platteville Pioneer Farm in Platteville, WI, and runoff collection systems will be installed. Runoff samples will be collected year-round, and analyzed for total sediment, total N and P, and dissolved P, NH4, and NO3. Initial and annual soil samples will be collected from plots and analyzed. Runoff plots will be stocked with dairy cattle to achieve several management scenarios with variations in diet supplementation and grazing intensity. These grazing strategies will result in different amounts of manure and associated nutrient amounts applied to runoff plots. After grazing periods, the number of dung pats deposited in each runoff plot section will be counted and collected to determine total wet weight, dry matter content, total P and N, and water extractable P. These data will enable quantification of nutrient inputs to the runoff plots in cattle feces. Runoff data will be used to validate our SurPhos model, which simulates dissolved P loss in runoff from surface-applied manure. Validation of the model will determine its ability to accurately simulate P loss in runoff from cattle grazing pastures. SurPhos is currently being adapted to simulate grazing and validating the model with field data from Australia and England and small-plot, simulated grazing data from several locations in the U.S. Information and data from Wisconsin producers will be used to simulate P loss from areas where cows spend time outside, including pasture, over-wintering areas, and barnyards. The physical locations and management practices that represent the greatest risk of P loss will be investigated to assess the ability of alternative practices to minimize that loss.
3. Progress Report
Four dairy grazing farms were identified and agreed to participate in the project. Each farm has been visited twice in 2011, once in the winter and once in the spring. At each visit, comprehensive herd, feed, and manure management information was collected. Milk analysis information was collected, and feed and manure samples were collected for lab analysis. The farms will be visited again in the late summer and fall. All this information will be used as input for the future model simulations. Eight pasture watersheds are fully instrumented with runoff monitoring and collection equipment at the UW Platteville Pioneer farm. Beef and dairy cattle grazed the pastures, runoff was collected for four background events and samples were analyzed for sediment, nitrogen, and phosphorus. Runoff from background events will continue to be collected during the summer and fall of 2011. Project monitoring was accomplished through e-mail exchanges, field site visits, a meeting among investigators to update project status and plan future goals, physical exchange of research samples, and electronic exchange of data.