ENERGY USE FOR FIELD OPERATIONS, CROP DRYING, AND SWINE HOUSING ON UNIVERSITY FARMS

Energy is an input to agricultural production. Knowing typical values can help farmers to evaluate management options. Diesel, propane, and electrical energy used on the farm during selected field operations, crop drying, and in swine housing were measured on Iowa State University research and demonstration farms. Baseline values were measured and tractor operation management styles were compared. Strategies for saving fuel were confirmed in 43 of 48 tractor operation comparisons. Comparisons of tillage depth, gear/engine speed, travel speed, and use of front-wheel-assist averaged 28%, 25%, 17%, and 13% more energy used than the fuel-saving alternative. Single-drive wheels used 8% more energy than duals, but results were mixed when comparing different tire inflation pressures. Energy used in high-temperature drying in bins ranged from 4.67 to 7.70 MJ kg(-1) (2010 to 3310 Btu lb(-1)). Most of the energy was from propane (96%). Propane use averaged 0.0027 L kg(-1) (0.018 gal bu(-1)) per percentage point of moisture removed. Minimum ventilation fans had the highest duty cycle in a curtain-sided swine finishing barn. Electrical use was greater in tunnel-ventilated than curtain-sided barns (29.0 vs. 20.9 kWh pig space(-1) yr(-1)) and propane use was greater in wean-to-finish than finish-only operations (10.6 L vs. 2.5 L pig space(-1) yr(-1), 2.8 gal vs. 0.67 gal pig space(-1) yr(-1)).