1a. Objectives (from AD-416):
The overarching objective of our research project is to address current knowledge gaps in understanding and managing the nutrient cycles and pathogen transmission on modern dairy farms. Our specific research objectives are as follows: 1. Determine the effects of dairy cattle diet and dairy herd management (e.g. pasture, confinement, hybrid systems) on manure nutrient excretion, capture, recycling, and loss via gaseous emissions, leaching, and runoff. 2. Determine the effects of dairy manure management practices and cropping systems on crop production, soil properties, and loss of nutrients, sediment, and pathogens (e.g. Cryptosporidium parvum, Salmonella spp., and bovine diarrhea virus) in surface runoff or atmospheric emissions. 3. Determine the effects of timing and rate of dairy manure application on nutrient uptake and nutritional characteristics of fresh and harvested annual and perennial forages. 4. Develop crop management strategies to optimize the exchange of N, P, and K as manure and feed between neighboring dairy and cash grain farms. 5. Develop improved methods for detection and quantification of pathogens in manure, forages, and surface runoff and evaluate effects of management practices on pathogen transport and survival.
1b. Approach (from AD-416):
Improved management of dairy farms requires successfully managing its nutrient flows, both to maximize nutrient use by animals and crops to optimize profit, and to minimize nutrient loss to the environment. We will investigate most aspects of nutrient cycling throughout the dairy-farm system with a variety of methods and at different scales (replicated field plots, field-scale paired watersheds, feeding trials with replicated pens of heifers, etc.). We will also examine pathogen transport and viability at different points in the dairy farm system. Some experiments will investigate only one or two nutrient or pathogen pathways, while others will be more comprehensive, including, for example, surface runoff, gaseous emission, and plant removal. Our research team also has a longer-term goal, which is to integrate information across experiments to more completely describe, quantify, model, and manage the entire dairy-farm nutrient cycle. Achieving this goal will help ensure the existence of sustainable, profitable, environmentally benign dairy farming for coming decades.
3. Progress Report:
The third year of a project measuring nutrient loss from different barnyard surfaces via runoff, leaching, and gaseous emission was completed. Results from the first two years were processed. A manuscript of gas emission results was submitted for publication. The results of a project evaluating nutrient runoff loss from different areas on dairy farms were summarized and submitted for publication. The model for phosphorus (P) loss from barnyards was completed and tested with literature data. We are collaborating with the Wisconsin Department of Natural Resources to use the model in Wisconsin, and with UW-Madison to generate barnyard runoff data for model validation. A project measuring nutrient loss in runoff from pastures and the whole farm ended in 2012. A final report was submitted to the Wisconsin Department of Agriculture, Trade, and Consumer Protection. The perennial forage phase (following a 5-yr corn silage phase) of a paired-watershed study to evaluate runoff losses of nitrogen (N), P, and pathogens from different manure/tillage/crop management systems was established. Collection and analysis of runoff samples from the calibration phase is ongoing. Working in collaboration with the US Geological Survey Wisconsin Water Science Center, the automated edge-of-field samplers were upgraded with new equipment and software to enable flow-weighted sampling of pathogens in runoff. The new system allows pathogen loading rates from field runoff to be calculated. A trial evaluating the effects of timing of manure application on alfalfa included the following treatments: i) no manure; ii) dairy slurry applied immediately after harvest; iii) dairy slurry applied after 1 week of regrowth; or iv) dairy slurry applied after two weeks of regrowth. Alfalfa was harvested from two cuttings and ensiled in wrapped large-rectangular bales. Bales have been sampled on a pre- and post-storage basis, and are now being prepared for transport to the University of Arkansas for evaluation of voluntary intake in growing lambs. In another trial, bedded-pack manure was evaluated against multiple rates of N fertilization with urea for a second year to support production of fall-grown oat forage. Data have been summarized, and the project will be repeated with dairy slurry in August 2013 and 2014. The second year of an experiment evaluating different low-disturbance manure application methods in a silage corn-rye cover system is in progress. Measurements of greenhouse gas emission, residue cover, and soil temperature and moisture are ongoing. Studies on the transport of manure-borne pathogens in Midwestern watersheds are continuing in collaboration with researchers at the US Geological Survey Wisconsin Water Science Center, Iowa Water Science Center, and Iowa State University. In addition, the microbiology laboratory has an ongoing study on the effectiveness of anaerobic digestion in removing pathogens in dairy manure. The study is unique in that it is quantifying removal of actual bovine pathogens, not indicator species, in full-scale digesters on seven dairy farms in Wisconsin.