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:
A five-year paired-watershed study to evaluate runoff losses of nitrogen (N), phosphorus (P), and pathogens from different manure/tillage/crop management systems was completed and data is being analyzed. The perennial forage phase of the experiment is being established. A series of rainfall simulation experiments to assess the effects of manure management and P supplementation of dairy heifer diets on runoff P losses was completed, and a journal article is in press. A runoff project comparing nutrient loss from different areas on a dairy farm was completed. Runoff samples have been analyzed and final results are being prepared. A preliminary model was developed for P loss in runoff from barnyards, and testing of the model is underway. The second year of runoff, leaching, and gas emission measurements from different barnyard surfaces was completed. Leachate and runoff samples are being analyzed for N and P. A new post-doc is processing gas emission data. The third year of a field trial to evaluate N availability and losses of ammonia and greenhouse gases from different methods and timing of liquid dairy manure application on corn was completed. Data analysis is in progress. A 2-year project on nutrient loss in runoff from pastures was completed. Runoff samples were analyzed and data were processed to estimate annual sediment and P loss in runoff. These and other data were used to validate the Annual P Loss Estimator (APLE) model, with excellent results. A study of four grazing-based dairy farms was conducted to determine relationships between nutrients (N and P) in feed, milk, and manure. Results showed differences compared to confinement-based farms. This information will help producers and consultants evaluate feed use efficiency and economic and environmental impacts of nutrient use on dairy farms. Data from these grazing farms are being compiled in APLE to estimate whole-farm P loss in runoff. In partnership with the University of Wisconsin, all summaries of studies evaluating supplementation of P for growing dairy replacement heifers have been completed and are now published. Plot studies evaluating the capacity of fall-grown oat to capture nutrients from manure or commercial fertilizer sources were conducted during Fall 2011, and will be repeated in Fall 2012-2014. Evaluation of the effects of manure application on subsequent silage fermentation characteristics of alfalfa were initiated in Summer 2012. Measurements of soil carbon and greenhouse gas emissions in a long-term (20-yr) cropping systems trial were completed. Studies are ongoing on the transport of manure-borne pathogens in Midwestern watersheds and groundwater aquifers in collaboration with researchers at the US Geological Survey Wisconsin Water Science Center, Iowa Water Science Center, Iowa State University, and the USEPA in Athens, GA. In addition, the microbiology laboratory launched a 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.
1. Managing manure to reduce runoff phosphorus (P) losses. Manure application to cropland can contribute to runoff losses of phosphorus, which can lead to excessive algae growth in lakes and streams. ARS researchers in Marshfield, Wisconsin, conducted a series of rainfall simulation experiments to assess how the amount of dissolved P in runoff would be affected by: 1) P supplementation of dairy heifer diets; 2) manure application method and rate; and 3) the amount of available P already in the soil. Phosphorus supplementation in the diet resulted in more P in manure, which led to 2 to 3 times more dissolved P in runoff. Incorporation of manure into the soil reduced runoff P concentrations by 85 to 90% compared to surface application. These results show that large reductions in P runoff losses can be achieved by avoiding unnecessary dietary P supplementation, by incorporation of manure, by limiting application rate when applying to cropland, and by avoiding soils with excessive P. By adopting these practices, farmers can greatly reduce the amount of P leaving their farms which subsequently will reduce algae growth and eutrophication in surface waters.
2. A user-friendly phosphorus (P) loss model improves predictions of surface water contamination with P. In response to concerns over P loss from agricultural fields and the impact on water quality, the USDA-Natural Resources Conservation Services (NRCS) revised its 590 Nutrient Management Standard to restrict P application to fields based on their risk of P loss. Most states use a P Index (estimate of potential P loss in water runoff) to assess a field’s risk of P loss, so producers are in compliance with these NRCS nutrient management policies. NRCS is now requiring states to demonstrate the accuracy of their Indexes and modify them if needed. ARS scientists in Madison, Wisconsin, and Bowling Green, Kentucky, evaluated one current P Index with measured P loss data from the published literature and found that the Index could be improved. They used their Annual Phosphorus Loss Estimator (APLE) model to develop alternative P Index formulations and weightings factors, and then showed that these alternatives greatly improved the correlation between P Index estimates and measured P loss from the published studies. Therefore, these new methods provide an easy, straightforward way to evaluate and improve P Indexes, which can help states comply with NRCS policies quickly and economically.
3. Improved assay for measurement of pathogens in water and manure. When using DNA-based technologies for quantifying pathogen levels in manure or the environment, there are naturally-occurring compounds that can inhibit the detection assay, causing it to fail or underestimate pathogen quantity. ARS researchers in Marshfield, Wisconsin, developed a method for accurately measuring the level of assay inhibition and mitigating the biasing effects of inhibitors. The method works in a variety of sample types such as groundwater, manure, or runoff from agricultural fields. Quantifying pathogens accurately in the environment is important for correctly identifying those management practices best suited for minimizing pathogen transport and maximizing pathogen removal. Such practices would benefit producers by preventing herd-to-herd disease transmission through environmental routes, and the public would benefit by preventing transmission of the types of pathogens found in dairy manure that are capable of infecting people.
Martinson, K., Coblentz, W.K., Sheaffer, C. 2011. The effect of harvest moisture and bale wrapping on forage quality, temperature, and mold in orchardgrass hay. Journal of Equine Veterinary Science. 31:711-716.