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Mid-County Agronomy
Controlling Soil Acidity
Hannah Schneider
Agronomy Intern
Controlling soil acidity is one of the most
important fertility management decisions.
As we go into fall, growers should look at
soil test recommendations for lime require-
ments.
Many factors aff ect soil pH including rain-
fall, the soil’s parent material, fertilizers, and
plant uptake. Diff erent crops require diff er-
ent soil pH levels for optimum performance
and when pH falls above or below these lev-
els, performance may suff er. The availability
of the nutrients phosphorus, potassium,
calcium, and magnesium signifi cantly de-
creases when the pH falls below 6.0. How-
ever, this low pH increases the availability of
the metallic micronutrients, like zinc, man-
ganese, copper, and iron.
Negatively-charged soil particles have
many diff erent sites where positively-
charged particles can attach. These sites are
referred to as cation exchange sites because
they attach positively charged cations such
as calcium (Ca2+), magnesium (Mg2+), po-
tassium (K+), sodium (Na+), hydrogen (H+),
and aluminum (Al3+). Cations can be clas-
sifi ed as basic or acidic. If released into the
soil solution, basic cations will increase the
pH and acid cations will lower pH. In order
to raise the soil pH, the acid cations have
to be removed from the cation exchange
sites and neutralized. When a liming mate-
rial such as calcium carbonate is added to
the soil, the calcium replaces the hydrogen
and/or aluminum and then the carbonate
neutralizes these cations.
Soils are limed to reduce the harmful ef-
fects of low pH including aluminum or
manganese toxicity and to add calcium and
magnesium to the soil. The amount of lime
needed to achieve a certain pH depends on
the pH of the soil and the buff ering capacity
of the soil. A soil with a large buff er capac-
ity (more clay size particles and/or organic
matter) will need more lime to neutralize
acidity than a soil with a small buff er capac-
ity.
The soil pH will tell you if a lime applica-
tion is needed. Lime recommendations will
vary from one fi eld to another depending
on current pH and desired pH, and the ca-
pacity of the soil to buff er changes in pH.
Mid-County
Agronomy hosted
several diff erent plot
days in August.
Personal VIP Plot Tours
are always available.
Call today at
(952) 466-3730
Plot Days
• Crop Protection • Nutrient Management • Crop Consulting
• Plant Food, Anhydrous, Lime, & VRT • Turfs & Pasture Management
• Producers, Croplan, Asgrow, Dekalb, NK Hybrids, & Stine
• Grid Sampling • Custom Anhydrous Application • Yield Mapping