1a. Objectives (from AD-416):
1: Develop process-level models to predict management effects on nutrient losses and gaseous emissions from farms. 1.A. Measure and model the crop production and environmental impacts of using new fertilizer technology. 1.B. Develop mechanistic relationships for the partitioning and transfer of volatile organic compounds from silage as affected by silage characteristics, management practices, and the environment. 1.C. Refine and evaluate process-level relationships for simulating ammonia, hydrogen sulfide, and greenhouse gas emissions from farms as influenced by animal, feed, and manure management. 2: Measure and model carbon sequestration potential of farming systems as a means of mitigating the impacts of agriculture on climate. 2.A. Measure the effect of enhanced nutrient availability on the carbon sequestration potential of permanent pastures. 2.B. Develop a sub-model for IFSM that represents belowground partitioning of assimilated carbon, soil respiration, and plant responses to current and elevated carbon dioxide levels. 2.C. Estimate carbon-sequestration potential of humid-temperate farm production systems using remote-sensing and associated models. 3: Refine and apply farm-scale models and analyze watershed data for integrated evaluations of management effects on nutrient losses, gaseous emissions, and the interacting effects on farm performance and profit. 3.A. Develop, evaluate, and release a Dairy Facility Gas Emission Model (DairyGEM) that expands the current DairyGHG model to include ammonia, hydrogen sulfide, and VOC emission predictions in addition to greenhouse gas emissions from dairy farms. 3.B. In support of the Conservation Effects Assessment Project, develop and apply methods for evaluating predictive uncertainty of individual and combined farm management practices. 3.C. In support of the Conservation Effects Assessment Project, publish a historical database collected from our Mahantango Creek experimental watershed to improve access, proper use, and long-term management of the data. 3.D. In support of collaborating projects working on air emissions, carbon sequestration, nutrient management, and bioenergy crop production, expand and use IFSM to evaluate the performance, environmental impact, and profitability of farming systems under historical and projected future climate scenarios.
1b. Approach (from AD-416):
Livestock operations can have a number of adverse impacts on the environment including nutrient leaching to ground water, nutrient runoff in surface water, emission of hazardous compounds to the atmosphere, and increased greenhouse gas emissions. These potential impacts are interrelated, so changes to reduce one environmental problem may increase another. A proper assessment of management changes and mitigation technologies requires a comprehensive approach that integrates all important environmental factors and their interactions along with effects on farm performance and profit. Process-level simulation, evaluated with experimental measurements, will be used to assess the environmental and economic implications of production strategies. This work will focus on further development, evaluation, and application of the Integrated Farm System Model and related software tools. Further development will improve the prediction of ammonia emission, add a component on hydrogen sulfide emission, and develop a component for predicting the emission of volatile organic compounds. An enhanced carbon sequestration component will model belowground plant processes, soil respiration, and crop responses to elevated carbon dioxide. Field and laboratory experimental measurements will help determine model parameters and provide data for model evaluation. The comprehensive models developed will be used to evaluate the effects of alternative technologies, management strategies, and climate on farm performance, environmental impact, and economics. The uncertainty of these complex models will be quantified through multiple simulations of given management practices across the ranges of relevant parameter inputs. The information and software produced will help direct producers and their consultants toward more environmentally and economically sustainable production systems.
3. Progress Report:
Gaseous loss data from field tests were completed, analyzed and reported. Cumulative growing season N2O emissions and grain yield were similar for all N sources in each year. Enhanced efficiency fertilizers did not appear to be an effective means of reducing N2O emission in a rain-fed system with below average rainfall. In laboratory column and field lysimeter N leaching studies, urea was found to leach through macropores under no-till conditions, so tillage that disrupts macropore flow reduces this loss. Data on volatile organic compound (VOC) concentrations, volatility and reactivity in the atmosphere were summarized through an extensive literature review, published, and used to refine and simplify our silage VOC emission model. A model based upon physical, biological and chemical principles was developed to predict VOC emissions from manure. Emissions from major groups of VOC compounds were adjusted for their smog forming potential and summed over all sources to estimate whole-farm emissions. The evaluation of N fertilization effects on pasture photosynthesis, respiration, and ecosystem C content was completed ahead of schedule. Mature pastures were a net C source to the atmosphere over a nine year period. Photosynthesis and respiration were highly correlated regardless of fertility level, so increasing N increased forage yield but not soil C sequestration. Existing routines were evaluated for estimating elevated atmospheric CO2 effects on pasture photosynthesis and yield and crop yield alone for alfalfa, corn, soybean, and small grains. The response was highly dependent on soil N fertility for non-leguminous crops and quantitatively and qualitatively matched published data. Legume photosynthesis and yield in pasture was also adequately simulated, but alfalfa and soybean yield enhancement by elevated CO2 was not as large as expected. The revised silage and the new manure VOC component models were incorporated in our DairyGEM software tool providing an educational aid for estimating ammonia, hydrogen sulfide, greenhouse gas, and now VOC emissions from dairy farms. The model was verified to predict reasonable emission levels for various silage and manure handling strategies, and actual emission data is now being collected from dairy farms for further model evaluation. Prediction uncertainty of farm management practices was evaluated under variations in precipitation and evapotranspiration and compared to published data to uncouple model, measured, and natural uncertainty. The beef production system used at the USDA/ARS Meat Animal Research Center was simulated using IFSM to evaluate environmental impact and production costs. For weather year 2011, simulated feed production and use, energy use, and production costs were within 1% of actual records. Simulation of their current production system gave 25 year annual carbon, energy, water and reactive nitrogen footprints of the beef produced, and simulations using historical production practices showed improvements made since 1970 and 2005.
Ghebremichael, L.T., Veith, T.L., Hamlett, J.M. 2012. Integrating watershed- and farm-scale modeling framework for targeting critical source areas while maintaining farm economic viability. Journal of Environmental Management. 114(0):381-394.