Manjula Nathan1, Peter Scharf2, and Yichang Sun2. (1) University of Missouri, University of Missouri, 23 Mumford Hall, Columbia, MO 65211, (2) Univ of Missouri, 108 Waters Hall, Columbia, MO 65211
In Missouri,
the Modified Woodruff Buffer (MWB) test is used to determine the lime
requirement in soils. Though this method has proven to work for Missouri soils it uses
para-nitrophenol as one of the reagents which is a hazardous substance. Also,
since Missouri is the only state in the nation
which uses the Woodruff Buffer test, it is better to evaluate the other buffer
tests used so that data and lime recommendations developed for Missouri can be compared
with similar information from the other states. Recent studies conducted in Maine, Pennsylvania and Virginia found the
Modified Mehlich Buffer (MMB) test to be a better method for determining lime
requirement in soils. Therefore, laboratory incubation studies were conducted
to evaluate MMB as an alternative to MWB for determining lime recommendations
for Missouri
soils. Twenty soil samples collected from different soil regions in Missouri that represent
major agricultural areas were used in the soil incubation study. Lime
requirement in the soils selected for incubation study was estimated by the MWB
test and the MMB test method. Soils were amended with reagent grade CaCO3 at rates of 0, 1/3, 2/3, 1 and
1 1/3 and 2 times the estimated lime requirement from the MWB method to raise
the soil pHs for target of 5.5-6.0, 6.0 -6.5, and 6.5 -7.0 ranges, and
incubated in the dark for a total duration of three months, with a three weeks
interval wetting and drying cycle. Soil pH was regressed with CaCO3 added to all 20 soils, and the
actual lime requirement was estimated for each soil to raise the soil pH to
target levels of 5.8, 6.3 and 6.8. MWB and MMB pHs were regressed against
actual lime requirement for all 20 soils to evaluate effectiveness of each test
for estimating the lime requirement in Missouri
soils.