175-11 Carbon Release From Steers and Fossil Fuels In Integrated Crop-Livestock Systems.

See more from this Division: Special Sessions
See more from this Session: Integrating Livestock Into Cropping Systems: Ecosystem Responses From Long-Term Studies
Tuesday, October 23, 2012: 3:05 PM
Duke Energy Convention Center, Room 262, Level 2
Share |

Cody J. Zilverberg1, Lisa Fultz2, Michael Galyean3, Jennifer Moore-Kucera2 and Vivien G. Allen2, (1)Natural Resource Management, South Dakota State University, Brookings, SD
(2)Plant and Soil Science, Texas Tech University, Lubbock, TX
(3)Animal and Food Sciences, Texas Tech University, Lubbock, TX
The use of fossil fuels and fossil fuel-derived products in U.S. agriculture increases productivity but also increases expenses, relies on non-renewable foreign energy, and releases CO2 to the atmosphere.  Quantifying and understanding agricultural fossil fuel use is important to improve efficiency.  We evaluated fossil fuel use and associated C emissions from three integrated crop-livestock systems in the Texas High Plains, ranging from low to moderate stocking rates and inputs ha-1.  All systems were grazed by stocker steers.  Systems were evaluated for 3 to 5 years in a randomized block design.  As stocking rate and quantity of inputs ha-1 increased, CO2 emissions associated with fossil fuel use increased from 752 to 2838 kg ha-1, primarily as a result of energy required to pump irrigation water (0 to 29% of total energy used), N fertilizer (13 to 25%), and the off-site cost of maintaining a cow herd to produce stocker steers (25 to 46%).  Efficiency of live weight gain did not differ (p > 0.05) between the most (49.9 MJ kg-1) and least (41.0 MJ kg-1) intensive systems.  Non-irrigated cotton emitted more CO2 (715 kg ha-1) than native grasses (110) or foxtail millet (528), but less than irrigated bluestem (979) and bermudagrass (1599).  Estimates of CH4 and CO2 from enteric fermentation and respiration by the steers, expressed as CO2 equivalents ha-1, were slightly greater in magnitude than CO2 emissions associated with fossil fuel use, ranged from 866 to 4825 kg ha-1, and increased with stocking rate.  Measurement of soil C indicated C is being sequestered most rapidly in the soils of the intensive system, but this may not compensate for greater rates of CO2, CH4, and NO2 release from fossil fuels, steers, and soils.  Improvements in cow-calf production and forage water- and N-use efficiency would decrease CO2 release associated with fossil fuels.
See more from this Division: Special Sessions
See more from this Session: Integrating Livestock Into Cropping Systems: Ecosystem Responses From Long-Term Studies