See more from this Session: Applying Soil Chemistry to Solve Soil Problems in the "Milky Way": Honoring the Impact of Malcolm Edward Sumner: III
Monday, November 1, 2010
Long Beach Convention Center, Exhibit Hall BC, Lower Level
, Plant, and Water Laboratory (SPW) uses a single-addition titration with Ca(OH)2 for estimating soil lime requirement University of Georgia Soil (LR). The LR depends in part on a soil’s pH buffering capacity (described as lime buffer capacity (LBC) with units of mg CaCO3 kg-1 pH-1) , which is estimated from the rise in soil pH after Ca(OH)2 is added and allowed to react for 30 min. This estimate of LBC is referred to as LBC30min. The 30-min reaction time has not been sufficient to reach an equilibrium pH between acid soils and Ca(OH)2, resulting in an underestimate of a soil’s true LBC. As a result, a correction factor has been applied to improve the accuracy of the LR. In a previous study in our laboratory, Thompson et al. (2010) showed that 25 soils from the Southeast US had reached an equilibrium pH by 84 h following Ca(OH)2 addition and that the LBC calculated using the equilibrium pH (LBCequil) could be predicted from the LBC30min. An accurate estimate of LBCequil should allow better lime recommendations across a range of initial soil pHs. The objective of the present study was to test the accuracy of an equation to predict LBCequil from LBC30min by determining if the LR calculated from LBCequil was more accurate than those calculated by the equations used presently. This was done by incubating 70 acid Georgia soils with amounts of Ca(OH)2 recommended using LBCequil to achieve a target pH of 6.0. Results of the incubations will be discussed with regard to improving the LR calculated with the new equations.