DBPapers
DOI: 10.5593/sgem2012/s16.v4006

EVALUATION OF THREE BUFFER METHODS FOR MEASURING THE LIME REQUIREMENT OF ACID COARSE-TEXTURED SOILS

M. C. CASSEUS LUC, A. KARAM, E. PARENT LEON
Wednesday 1 August 2012 by Libadmin2012

References: 12th International Multidisciplinary Scientific GeoConference, www.sgem.org, SGEM2012 Conference Proceedings/ ISSN 1314-2704, June 17-23, 2012, Vol. 4, 81 - 90 pp

ABSTRACT

Information on the ability of lime requirement (LR) methods to predict the amount of
lime required to achieve a selected pH that if optimum for crop production is important
in the management of acid agricultural and horticultural soils. The primarily aim of this
study was to evaluate three quick buffer methods for measuring LR to target pH values
using 28 acidic coarse-textured soils from Quebec (Canada). The buffer methods
included the original Shoemaker, McLean and Pratt (SMP) single-buffer method (initial
buffer pH 7.5) and modified SMP method (initial buffer pH of 6.0 and 5.5, and soil:
CaCl2 0.01 M:buffer solution ratios of 1:1:2 and 1:2:2), the Adams and Evans (AE)
method (initial buffer pH 8.0) and the Mehlich single-buffer method (initial buffer pH
6.6). The SMP procedures were compared on the basis of their ability to predict the lime
requirement to pHwater values of 5.5, 6.0 or 6.5, and to pHCaCl2 values of 5.0 and 5.5
obtained from soil-CaCO3-moist incubation (ILR). LR values estimated from all
procedures were significantly correlated with each other. Decreasing SMP buffer pH
from 7.5 to 5.5 gave an accurate and precise estimation of the soil LR. In general, the
best linear relationships between the ILR and soil:water:buffer equilibrium pH or
soil:CaCl2:buffer equilibrium pH were obtained when the initial SMP buffer solution
was adjusted to pH 5.5. The relationship between ILR and SMP-LR at 1:1:2
soil:CaCl2:buffer solution is better than that obtained at 1:2:2 ratio. Positive correlations
were obtained between SMP-LR values and total and exchangeable acidity, extractable
soil Al (AlCaCl2, AlKCl, Aloxalate, Aldithionite and Alpyrophosphate), and organic matter and clay
particle content. The results indicate that the LR determination of acid coarse-textured
soils is affected by soil buffer equilibrations and chemical properties that are associated
with acidity factors and buffer capacity.

Keywords: soil acidity, exchangeable acidity, buffer capacity, soil testing.

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