Lime Cost-Effective In Correcting The pH Of Acidic Soil
BLUE SPRINGS, MO.
Liming is an inexpensive way to boost crop
yields in fields with overly acidic soils, said
a University of Missouri Extension agronomy
specialist.
A soil pH of 6.0 to 6.5 is optimum for most
crops in Missouri, said Travis Harper, a University
of Missouri Extension agronomy specialist.
Soil pH affects the availability of soil nutrients
to plants. An increase in soil acidity (lower pH)
reduces the amount of available phosphorous in
the soil while increasing the amount of available
aluminum and hydrogen. At a pH of 4.5, available
aluminum and hydrogen are at toxic levels,
he said.
To counter these effects, an application of lime
can reduce soil acidity. Liming increases the activity
of organisms responsible for nitrification
and nitrogen fixation and improves the overall
condition of the soil.
“MU research indicates that increasing the pH
of a soil from 4.5 to 6.0 through liming can increase
soybean yield by as much as 15 percent,”
Harper said. “Given the benefits of liming, and
the fact it is one of the cheapest products farmers
add to the soil, there should be no reason
the pH levels of Missouri agricultural soils don’t
fall within the ideal range.”
A soil test, available through local MU Extension
centers, can measure soil pH and indicate
the amount of lime necessary to neutralize soil
acidity.
The amount of lime to apply is expressed in
terms of “effective neutralizing material” (ENM).
All lime sold in Missouri is tested for purity and
fineness, the two factors that determine the
ENM of a lime product.
“For example, a soil test may indicate that a
soil is acidic and needs 1,200 ENM to increase
the pH,” Harper said. “If lime from a dealer is
400 ENM per ton, the farmer would need to
apply three tons to correct the soil pH.”
The main disadvantage with lime is that it can
take a long time to correct soil acidity, especially
if it’s not properly incorporated. MU research indicated
it would take 10 to 14 years for surfaceapplied
lime without incorporation to raise the
soil pH to a depth of 6 inches. All applied lime
should be incorporated for maximum effectiveness.
Even with incorporation, it may take several
months for lime to correct soil pH. For this reason,
don’t apply lime in March in an attempt to
correct the soil pH for a crop you are going to
plant in April.
“An ideal situation would be to take a soil sample
right after harvest, then apply and incorporate
the recommended amount of lime that fall,”
Harper said. “There should be sufficient correction
in soil pH by the following spring to have a
positive impact on crop growth.”
The MU Extension guide “Liming Missouri
Soils” (G9102) is available online at
extension.missouri.edu/publications/DisplayPub.aspx?P=G9102.
For information about MU Extension soil and
plant testing services, see soilplantlab.missouri.edu/soil/. Δ