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United States Department of Agriculture

Agricultural Research Service

2009 Annual Report

1a.Objectives (from AD-416)
The primary objective of the project is to address current knowledge gaps in understanding and managing the nutrient cycles of modern dairy farms. Under this broad research umbrella are five specific objectives: i) to determine the effects of dairy diets and herd management on manure nutrient excretions and nutrient losses to the environment; ii) to determine the effects of manure and crop management practices on nutrients, sediment, and pathogens in surface runoff and other pathways; iii) to determine the effects of season, dairy diet, and field management of manure on gaseous emissions of NH3, N2O, CO2, CH4, and volatile organic compounds; iv) to determine the effects of mechanical application of dairy manure on nutrient uptake and nutritional characteristics of annual and perennial forages; and v) to develop conventional and organic crop management strategies to facilitate the exchange of N, P, and K as manure and feed between neighboring dairy and cash grain farms.

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 in order to optimize profit, and to minimize nutrient loss to the environment in order to optimize sustainability. 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.). Some experiments also include non-nutrient elements such as eroded sediment and pathogens. Specific experiments will investigate only one or two nutrient pathways that, taken alone, may seem unrelated. However, our research team has a longer-term goal that will be achieved in future CRIS cycles, 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 second year of manure treatments was applied to runoff plots comparing corralling areas, pastures, and cropped fields in 2008 and 2009. Barnyards to evaluate runoff, drainage, and volatile N and P losses from different ground surfaces were substantially constructed. The calibration period of a paired-watershed study to evaluate runoff losses of N, P, and pathogens from different manure/tillage/crop management systems was completed, data was summarized, and treatments were established. A field trial on dairy heifer management impacts on manure nitrogen collection and cycling through crops was completed, analyzed and the results were published. The effects of forage protein-binding polyphenols on the chemistry of dairy excreta were assessed. The slurry collected from this trial was land-applied to examine possible links between diets, excreta chemistry and the availability of excreta N to subsequent corn silage crops. A field trial to evaluate nitrogen availability from different methods and timing of liquid dairy manure application on corn was established and ammonia emission from first-year treatments was measured. On-farm trials on manure use on orchardgrass and on the production of organic feed grains are in their final year. Seasonal ammonia emissions from three Wisconsin dairy farms were measured, analyzed and the results were published. A ‘tool kit’ for making snap-shot assessments of nutrient use efficiency on confinement dairy farms was developed and made available on the Internet. An improved incubation protocol for soil organic carbon was developed and analysis is progressing. Soil in a long-term cropping systems trial was sampled to assess soil quality and most analyses have been completed.

1. Snap-shot Assessment of Nutrient Use Efficiency on Confinement Dairy Farms Nutrient use efficiency can be broadly defined as the relative amount of feed, fertilizer and/or manure nutrients inputs that are incorporated into milk, crops/pasture or other outputs. Relatively little information is available on nutrient use efficiency on commercial dairy farms, or on how it can be measured and evaluated for impacts on profitability and environmental performance. Over the past several years, researchers at the U.S. Dairy Forage Research Center and the University of Wisconsin-Madison have developed tools that can be used to provide snap-shot assessments of feed, fertilizer, and manure use on dairy farms in various settings. A website was developed that contains a (1) Fact Sheet giving an overall explanation of nutrient use efficiency, the importance of knowing it, and how to measure it; (2) Nutrient Management Survey questionnaire; (3) Manure Spreading Book – a document to help dairy producers keep track of when, where, and why they spread manure; (4) an example of a Final Farmer Report; and (5) four scientific journal articles related to nutrient use efficiency on confinement dairy farms.

2. Diets Including Forages for Developing Replacement Heifers Require No Supplementation of Phosphorus When phosphorus is fed to cattle in amounts greater than they can utilize, the excess is excreted in the manure. If phosphorus-rich manure is later spread on farm fields to provide nutrients for growing crops, it also may cause an excess of phosphorus in runoff that can promote the undesirable growth of algae in lakes. For growing dairy heifers, phosphorus is essential for bone growth and development. The amount of dietary phosphorus needed in dairy heifer diets is very similar to that found naturally in many forages comprising typical heifer diets. Scientists from the University of Wisconsin-Madison and the U.S. Dairy Forage Research Center conducted a long-term trial on phosphorus supplementation with heifers ranging from 4 to 22 months of age. Heifers were fed diets with or without supplemental phosphorus resulting in dietary phosphorus concentrations of 0.29 or 0.39%. We intensively evaluated bone growth, composition, and metabolism on a sub-group of these heifers. Our results show that phosphorus supplementation for developing replacement heifers had minimal effect on the extent of frame development, bone density, or bone metabolism. A parallel experiment evaluating runoff from simulated rain on applied manures from heifers in this study showed that incorporating manure reduced P losses in runoff by 85-90%, and that manure from heifers fed unsupplemented diets resulted in lower P concentrations in runoff solids than those fed P-supplemented diets. This information will help dairy producers and nutritionists formulate heifer rations that contain adequate, but not excessive, amounts of phosphorus so that the growth needs of the heifers are met without adding excess phosphorus to the environment.

3. Ammonia Emissions from Wisconsin Dairy Farms Smaller Than Estimates Used by Policy Makers Ammonia in the atmosphere is an environmental concern because it is the primary basic gas that neutralizes acidic atmospheric gases produced from the combustion of fossil fuels; this reaction produces an aerosol that is a component of atmospheric haze, and is implicated as a potential human health hazard. Ammonia is emitted from dairy farms, but there has been little data quantifying the amount emitted, or whether this amount varies from season to season or with different dairy management options. We conducted studies to obtain representative and accurate ammonia emissions data from large dairy farms in Wisconsin. Ammonia concentrations and climatic measurements were made on three dairy farms (>800 cows) during the winter, summer, and autumn. During autumn and summer, whole-farm emissions were significantly greater than observed during winter with about two-thirds of the total emissions originating from the waste management systems. The mean whole-farm winter, autumn, and summer ammonia emissions were 1.5, 7.5, and 13.7% of feed nitrogen inputs, respectively. Average annual emissions comparisons between the three farms were similar at 7.0, 7.5, and 8.4% of input feed nitrogen emitted as ammonia, with an annual average for all three farms of 7.6 ± 1.5%. Our results showed that ammonia emissions from Wisconsin dairy farms were considerably smaller than currently-used estimates for dairy ammonia emissions; and they were significantly smaller than measured emissions from other types of animal-feeding operations. This information can help dairy producers reduce ammonia emissions from their farms; and it provides other scientists and policy makers with more accurate, scientifically based information about dairy farming’s impact to the environment.

4. Model Shows the Influence of Storm Hydrology on Manure Phosphorus Loss in Runoff Non-point source pollution of fresh waters by agricultural phosphorus (P) can limit water use for drinking, recreation, and industry. One major source of P loss in surface runoff is unincorporated manure. The few studies that investigated increasing the time between manure application and the first rain-runoff event as a way to decrease manure P loss did not fully consider the effect of storm hydrology. ARS scientists at the Dairy Forage Research Center in Wisconsin used a recently developed manure P runoff model to show that storm hydrology is a major factor controlling how much manure P can be lost in runoff. Other factors such as soil adsorption of manure P or manure drying are not nearly as important. This work will help scientists and producers better understand how timing of manure applications to fields can be used to decrease runoff P loss.

5. Economics of Hauling Dairy Slurry and its Value in Wisconsin Corn Grain Systems. Fertilizer prices have risen to record highs in recent years, negatively impacting grain farmers who typically rely on purchased fertilizer inputs for crop production. At the same time that fertilizer prices are climbing, expansion within the dairy industry has left some dairy farmers confronted with larger and larger quantities of manure to manage. To evaluate the potential of using dairy slurry for corn (Zea mays L.) production in Wisconsin grain systems, custom manure hauler bids were combined with corn production expenses to develop enterprise budgets in which slurry provided corn nutrient needs. A scenario was developed in which a recipient grain farmer shares manure hauling costs with the dairy farmer supplying slurry to his/her fields. Results showed that by sharing manure hauling expenses, profitable hauling distances more than doubled from 3.2 km when a dairy farmer spreads manure on his/her own crops to 7.6 km when slurry is hauled to a neighboring grain farmers fields. These results indicate that in spite of its weight and low nutrient concentration, dairy slurry is competitive with commercial fertilizer for crop production at relatively great hauling distances.

5.Significant Activities that Support Special Target Populations
We continued research on dairy farms having small to medium herd sizes (100 to 200 dairy cows/farm) to understand the impact of biophysical (soils, weather) and socioeconomic factors on nutrient (feed, fertilizer and manure) management practices and the opportunities and challenges to improvements in profitability and environmental impacts through enhanced nutrient use.

Review Publications
Esser, N.M., Hoffman, P.C., Coblentz, W.K., Orth, M.W., Weigel, K.A. 2009. The Effect of Dietary Phosphorus on Bone Development in Dairy Heifers. Journal of Dairy Science. 92:1741-1749.

Vadas, P.A., Good, L.W., Moore Jr, P.A., Widman, N. 2009. Estimating Phosphorus Loss in Runoff from Manure and Fertilizer for a Phosphorus Loss Quantification Tool. Journal of Environmental Quality. 38:1645-1653.

Powell, J.M., Grabber, J.H. 2009. Dietary Forage Impacts on Dairy Slurry N Availability to Corn. Agronomy Journal. 101:747-753.

Russelle, M.P., Blanchet, K.M., Randall, G.W., Everett, L.A. 2009. Characteristics and Nitrogen Value of Stratified Bedded Pack Dairy Manure. Crop Management. Available:

Jokela, W.E., Grabber, J.H., Karlen, D.L., Balser, T.C., Palmquist, D.E. 2009. Cover Crop and Liquid Manure Effects on Soil Quality Indicators in a Corn Silage System. Agronomy Journal. 101:727-737.

Hanrahan, L.P., Jokela, W.E., Knapp, J.R. 2009. Dairy Diet Phosphorus and Rainfall Timing Effects on Runoff P from Land-Applied Manure. Journal of Environmental Quality. 38:212-217.

Last Modified: 9/1/2015
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