Start Date: Feb 15, 2013
End Date: Feb 14, 2014
For the first objective, experiments will be conducted at the ARS facilities in Prairie du Sac & Marshfield, WI. Experiments at Prairie du Sac will investigate relationships between the amount and form of C and N in dairy diets and production and characteristics of milk, manure, and C and N gas emissions. For example, we will expand research of dietary C impacts on dry matter intake, milk production, and enteric CH4 to include impacts of dietary C and feed additives (e.g., tannins, fats, oils, Monensin, & oregano) on rumen protozoal numbers and activity, feed C and N use efficiency, manure C chemistry, CH4 emissions during manure storage and C dynamics in soil, including manure C and N mineralization and C sequestration. We will also expand investigation of dietary crude protein (CP) impacts on milk production, milk urea N (MUN) & NH3 emissions from barns and soils to include new investigation of dietary CP impacts on manure N chemistry and soil, water and air quality, including plant N availability, nitrate leaching and N2O emissions. This research thus investigates a range of management practices to reduce enteric CH4 emissions and enhance crop-soil and manure management. At Marshfield, we will add or enhance existing C and N gas emissions measurements to ongoing field trials that evaluate manure management effects on crop yield, nutrient runoff, ammonia emission, and/or gas emission at plot and field scales. These experiments include 1) low-disturbance manure application methods for silage corn/rye cover crop system (strip-till/manure, sweep injection, coulter injection, aerator-band, and broadcast); 2) improved manure application methods for alfalfa-grass (band application, aerator-band, shallow injection, & broadcast); and 3) paired-watershed study to compare crop/manure/soil management for perennial forage systems. For the second objective we will evaluate and compare existing, commonly used process models (e.g. CENTURY, EPIC/APEX, DNDC, IFSM, & Cornell CNCPS) and apply them to assess global warming mitigation and adaptation at regional levels with a special focus on C, N, and water fluxes. Process modeling extension will start by a detailed comparision of several models (CENTURY/Daycent, DNDC, EPIC/APEX, & IFSM). Based on our preliminary results, we expect that N2O and other N fluxes, both from soil/feed production and from animal production, will be a main source of the difference. For each important difference between models, we will analyze in detail which mechanisms are involved, and the source of the differences, and we will identify needs for both model harmonization and additional model improvements. These comparisons will be carried out based on a set of five pilot dairy farms covering a range of practices and located in different states throughout the Upper Midwest & Northeast. Comparisons/evaluations of models will be conducted for the appropriate scale, either field (DNDC), farm (IFSM), or region (EPIC/APEX). Comparisons with measured data from the first objective will then be able to discriminate between model differences, make adequate choices & identify where further model developments and field monitoring are needed.