Impact of Animal Manure Addition on Agricultural Lime Weathering in Acidic soil: PH Dependence and CO2 Independence of Agricultural Lime Weathering

To ascertain the impact of animal manure addition on aglime weathering in acid soil and to understand the contribution of carbonate weathering to the atmospheric/soil CO2 in acid soil profile, two contrastive profiles (control profile and manurial profile) in the HuaXi district of Guiyang, China were established, and carbonate rock tablets were buried in different depths of soil profiles to determine the weathering rate of aglime. The results showed that soil CO2 increased owing to animal manure addition, but the dissolution of carbonate rock tablets decelerated, which was attributed to the increase of pH in acidic soil after animal manure addition. The relationship between the dissolution rate of carbonate rock tablets and soil pH indicated that the weathering rate of aglime was controlled by pH rather than CO2 in acid soil. Thus, the contribution of protons in acidic soil as a weathering agent to riverine alkalinity may lead to the overestimation of CO2 consumption via chemical weathering at regional/global scale using hydrochemical methods.