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United States Department of Agriculture

Agricultural Research Service

2010 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
We have continued research to improve manure nutrient use efficiency & assess losses via different pathways - surface runoff, leaching, gaseous emissions - in various dairy farm crop & animal management systems. The 3rd & final year of the runoff experiments at the Prairie du Sac farm comparing nutrient runoff loss from corralling areas, pasture, & cropped fields on a dairy farm will be completed in Fall 2010. Data will be summarized & publications prepared in 2011. The treatment period of a paired-watershed study to evaluate runoff losses of nitrogen (N), phosphorus (P), & pathogens from different manure/tillage/crop management systems is in its 2nd year; data from the calibration period was summarized & a manuscript submitted for journal publication. Construction of barnyards having solid, sand or wood chip surfaces was completed & measurements of runoff & leaching initiated. A new model for grazing cattle dung decomposition & phosphorus transformations & loss in runoff was developed & validated. This model will enable better quantification of P loss from cattle grazing areas & better comparison of the environmental impact of dairy production systems, including confinement & grazing operations. New assays for determining chemistry of dairy feces & urine, & methods for measuring ammonia & Greenhouse Gas (GHG) flux from soil have been developed. The 2nd year of a field trial to evaluate N availability & ammonia losses from different methods & timing of liquid dairy manure application on corn is in progress; a component to measure GHG flux has been added. The correspondence between measurements of ammonia emission from dairy barns at various scales was published in a conference proceeding. A manuscript on nitrogen use efficiency in dairy production was published based on a literature review, data collected on dairy farms in Wisconsin & Australia, & output from the Integrated Farm System Mode. 'Trends in The US Dairy Industry' was published as a contribution to a global study ‘Livestock in a Changing Landscape' commission by the United Nations. 'Snap-shot' tools for assessment of nutrient use efficiency in dairy production were further developed & applied to resource-poor, small-holder dairy farms in Uttar Pradesh, India. Twenty years of soil sampling to assess the impact of cropping systems on soil fertility & carbon characterization were completed this year & manuscripts are being written. Soil quality assessment of long-term cropping systems was completed & the data was summarized & reported in a university publication. On-farm & on-station trials studying the impact of expanding the use of manure grain systems has found that weed pressure does not increase, compaction can be avoided, grain yield increases & at hauling distance of less than 7km, if manure application costs are shared, it is less expensive to apply than commercial fertilizer.

1. Nitrogen use efficiency in dairy production. The more efficient dairy farmers are in managing nitrogen (N), the more milk their cows will produce & the less (N) will be wasted in manure. ARS Researchers in Madison, Wisconsin, & University Park, Pennsylvania, along with Australian colleagues, calculated (N) use efficiency ratings to guide dairy farmers. These ratings could help dairy farmers make better use of their (N) in the face of escalating costs & increasing nutrient regulation. Farmers feed (N) in the form of crude protein to their cows, & apply manure & (N) fertilizer to grow crops & pasture for cows to eat & convert to milk. The scientists found that only about 20-35% of the (N) fed to dairy cows is converted into milk. They also discovered that 16 -77% of the (N) in manure or fertilizer is taken up by crops & pasture plants. Their study also showed that between 8- 64% of all (N) applied to typical commercial dairy farms is converted into farm products. Whole farm (N) use efficiency was determined by applying the ARS-developed Integrated Farming System Model on two typical dairy farm types in Wisconsin. The model was used to quantify the effects of numbers of cows per acre & manure (N) credits (reducing fertilizer (N) applications when manure is applied) on (N) use, farm profitability, & pathways of (N) loss. The wide ranges in (N) use efficiency indicate that there is significant room for improvement by using various practices that improve (N) use, profits, & the environment. (N) use efficiency formulas can be used as tools to promote practices that maximize (N) use so that (N) does not leave farms to pollute waterways and ground water & negatively impact air quality. From these tools may come recommendations to dairy farmers, consultants, and policy-makers.

2. The United States: Trends in the dairy industry and their implications for producers and the environment. The United Nations Food and Agriculture Organization (FAO) and its international collaborators published ‘Livestock in a Changing Landscape’, which examines the drivers, consequences and responses to the global livestock revolution. This contribution by scientists at the US Dairy Forage Research Center examines the reasons for, and consequences of, excessive nutrient use on dairy farms, and governmental policy and industry responses to public concerns related to improving environmental impacts of dairy farming systems. The on-going trend towards fewer and larger dairy farms has encompassed a greater use of imported feed, and the production of quantities of manure nutrients which can exceed the recycling capacity of associated pastures and croplands. The liberal use of cheap fertilizers, in combination with manure and other agricultural nutrient sources, can result in numerous adverse environmental impacts, including damage to water quality through runoff and leaching, and gaseous emissions that can adversely affect human health, fertilize natural ecosystems and contribute to global climate change. Important farm operational features and management options could be targeted to enhance nutrient use and environmental performance including maintaining the balance between livestock numbers and pasture/cropland available for manure land-spreading; optimal livestock feeding; and the abilities of farmers to collect and land-spread manure under the diverse biophysical and socioeconomic conditions they face. New partnerships among research, extension, feed and fertilizer industries, policy makers and crop and dairy producers are needed to evaluate and enhance the environmental performance of dairy farming in the USA.

3. New model developed to predict grazing cattle dung phosphorus cycling. Non-point source pollution of fresh waters by agricultural phosphorus (P) can limit water use for drinking, recreation, and industry. Little information exists comparing P loss in runoff from different dairy production operations, especially grazing operations. ARS researchers at Madison, WI developed and validated a new computer model to predict grazing cattle dung decomposition and P transformation and loss in runoff. The model will help scientists quantify the environmental impact of grazing operations, especially in comparison to confinement operations, and will help them identify management practices that can minimize P loss in runoff.

4. Phosphorus routines in the SWAT computer model improved. The Soil and Water Assessment Tool (SWAT) is used throughout the world to estimate the environmental impact of non-point source pollution of agriculture phosphorus (P). ARS researchers at Madison, WI assessed the ability of routines in SWAT to accurately simulate soil P content and changes in soil P availability, which are critical to accurately simulate P loss in runoff. Researchers found SWAT routines will generally underestimate soil total P and will underestimate P availability for several weeks after P is added to soils. They proposed alternative routines to correct these SWAT shortcomings. Results will help improve the SWAT model and its ability to accurately assess the environmental impact of agricultural operations.

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
Coblentz, W.K. 2010. Effects of Wrapping Method and Soil Contact on Hay Stored in Large Round Bales in Central Wisconsin. Applied Engineering in Agriculture. 25:835-850.

Coblentz, W.K., Walgenbach, R.P. 2009. Fall Growth, Nutritive Value, and Energy Density for Cereal-Grain Forages in the North-Central United States. Journal of Animal Science. 88:383-399.

Coblentz, W.K., Hoffman, P.C., Martin, N.P. 2010. Effects of Spontaneous Heating on Forage Protein Fractions and In Situ Disappearance Kinetics of Crude Protein for Alfalfa-Orchardgrass Hays Packaged in Large-Round Bales. Journal of Dairy Science. 93:1148-1169.

Powell, J.M., Gourley, C.P., Rotz, C.A., Weaver, D.A. 2010. Nitrogen Use Efficiency: A Performance Indicator for Dairy Farms. Environmental Science and Policy. 13:217-228.

Carter, J.E., Jokela, W.E., Boxworth, S.C. 2010. Grass Forage Response to Broadcast or Surface-Banded Liquid Dairy Manure and Nitrogen Fertilizer. Agronomy Journal. 102:1123-1131.

Hedtcke, J.L., Posner, J.L., Hall, J.A., Walgenbach, R.P. 2010. Orchardgrass Ley for Improved Manure Management in Wisconsin: I. Forage Yield, Environmental Impact, and Production Costs. Agronomy Journal. 102:1-9.

Last Modified: 9/5/2015
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