HR: 0800h
AN: B41B-0191    [Abstracts]
TI: Estimating Net CO2 Emissions From Agricultural Lime Applied to Soils in the U.S.
AU: * McBride, A C
EM: allen.mcbride@duke.edu
AF: Program in Ecology, Duke University, Durham, NC 27708 United States
AU: West, T O
EM: westto@ornl.gov
AF: Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6335 United States
AB: Agricultural lime in the form of crushed limestone and dolomite is applied to U.S. agricultural soils at a rate of 20-30 Tg yr^-1. Understanding the ultimate fate of applied lime and associated carbonate species is important for estimating net CO₂ emissions from agricultural lime. We provide a history of lime use in the U.S., estimate the fraction of dissolution by acid species, discuss transport of lime constituents through the soil profile, and estimate the transport of these constituents in rivers and to the ocean. Previous estimates of net CO₂ loss from agricultural lime assume that all CO₂ in lime is eventually released to the atmosphere. Our analyses suggests that, as a first approximation, about 50% of the CO₂ in lime is released to the atmosphere. This estimate translates to 0.059 Mg C per Mg limestone and 0.064 Mg C per Mg dolomite, and 4.4-6.6 Tg CO₂ emissions in 2001, depending on the total application of agricultural lime in the U.S. This estimate largely depends on the pathways of lime dissolution and the fraction of bicarbonate leached through the soil profile. If carbonate species are accumulating lower in the soil profile, then our estimates of net CO₂ emissions from agricultural lime may be overstated. However, if carbonate from lime is transported down rivers to the ocean, as is suggested by data from the Mississippi watershed, then the application of aglime may be impacting carbon cycling in the coastal ocean. A more complete understanding of net CO₂ emissions from aglime will contribute to bottom-up estimates of CO₂ emissions from agricultural lands, and these estimates are also applicable to terrestrial carbon accounting.
DE: 0402 Agricultural systems
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0460 Marine systems (4800)
DE: 0486 Soils/pedology (1865)
SC: Biogeosciences [B]
MN: Fall Meeting 2005