LATEST RESEARCH IN
LIME RECOMMENDATIONS
AN EVALUATION OF LIME
REQUIREMENT METHODS
USED FOR SOUTH AFRICAN
SOILS
Vincent van der Berg, Dr Aisla Hardy &
Dr Pieter Raath
In collaboration with
Stellenbosch University, Bemlab
recently conducted a M.Sc Agric
study (Vincent van den Berg)
to evaluate several widely used
methods to predict soil lime
requirements, using 20 acidic
South African top and sub-soils
(Western Cape, Eastern Free
State, Northwest, KwaZulu Natal)
with a wide range of properties.
Seven soil lime requirement
methods that are currently used
in South Africa were evaluated
against a standard CaCO 3
incubation soil lime requirement
procedure.
1. the original Eksteen method with organic
matter correction factor (OMCF) , commonly
used in the Western Cape;
2. two modifications of the Eksteen method,
namely:
a. Eksteen-KCl method, where the use of 1M
KCl exchangeable acidity instead of titratable
acidity at pH 7, and
b. Modified-Eksteen method, where a correction
factor was applied to titratable acidity that was
derived from soil data obtained in this study;
3. the Cedara method, most commonly used in
KwaZulu-Natal;
4. the ARC-SGI method, developed primarily
for Free State soils by the ARC- Small Grain
Institute in Bethlehem;
5. the Shoemaker-McLean-Pratt single buffer
(SMP-SB) method most commonly used in the
North East and North Central regions of the
USA;
TECHNICAL
6. the Adams and Evans single buffer (AE-SB)
method mo st commonly used in the South East
and Mid-Atlantic regions of USA.
T
he original Eksteen and Cedara methods
were found to be highly correlated with
incubation soil lime requirement, yet
consistently underestimated soil lime requirement.
The modified-Eksteen method, however, was found
to be highly correlated with incubation soil lime
requirement, and was a good predictor of soil lime
requirement. In fact, titratable acidity was found
to be the soil property that most strongly related
to soil lime requirement. The ARC-SGI method
was a considerably poor predictor of soil lime
requirement, and tended to grossly
overestimate soil lime requirement.
The two buffer methods were also
highly correlated with incubation
soil lime requirement, and with some
recalibration resulted in having a
high accuracy of predicting soil lime
requirement. Since the buffer methods
are difficult to implement commercially,
the most accurate method at our
disposal for determination of soil
lime requirement on a wide range of
soils from this study was the modified
Eksteen method.
The combination of soil properties
(Table 5-4) that most strongly
influenced the SOIL LIME
REQUIREMENT of each method were evaluated
in the study.
The results from this study indicate that the most
vital soil properties that need to be determined
in order to sufficiently estimate the SOIL LIME
REQUIREMENT of a soil are, in no particular
order: Walkley-Black C, titratable acidity at pH 7.0,
exchangeable cations, buffered CEC at pH 7.0 and
texture. Considering these findings, however, it is
crucial that more research be carried out in order to
evaluate the economic implications of basing SOIL
LIME REQUIREMENT on the above-mentioned
soil properties, in relation to crop performance and
long-term soil management method.