Wednesday, November 15, 2006

Efficacy of Liming Materials in the Context of New Lime Regulations.

William Evans and J. Larry Oldham. Mississippi State Univ, 2024 Experiment Station Rd, PO Box 231, Crystal Springs, MS 39059-0231

Ten liming materials and one untreated control are being compared in a long-term study of liming material influences on pH and other soil parameters in a central Mississippi silt loam.  Treated plots received a surface application of 4.5 Mg.ha-1 of their assigned material in April 2005.  The material was then tilled into the surface 15 cm on the day of application.  Plots were sampled at 0, 30, 60, and 90 days after treatment (DAT), then approximated every 90 days through summer, 2006.  Pre-application soil pH ranged from 6.4 to 6.6 among the four replicates.  At 366 and 455 DAT, all treatments had significantly higher mean pH than the untreated control, with mean pH ranging from 6.5 in the untreated control to nearly 7.9 in the treatment with the highest mean pH.  Mean soil pH in one treatment was consistently higher than all or most other treatments at each sampling date.  Soil pH changes in response to treatment have differed indicating significant differences in the influence of the materials on soil pH under the Crystal Springs conditions to date.  No treatments have shown a trend toward return to pre-treatment levels as of July 2006.  The study will follow soil pH in the plots for thirty-six months or until there is significant decrease in pH down to or near the initial pH levels.  This will provide information about absolute pH changes and the progression of change over time for the materials being tested.  The information will be matched to sieve and other liming material quality tests of each material to further assist users in selection of liming materials appropriate for the intended use in the context of current lime regulations.