soil Acidity and Liming
Introduction
Soil acidity is a major concern in Massachusetts. Correcting soil acidity (pH) is a
fundamental step in productive plant growth. The pH of a soil should always be tested
before making management decisions that depend on the soil pH.
Why do soils become acidic?
The major causes of acidity are:
Acidic parent materials: Soils that developed from certain material such as granite are
likely to be more acidic than those developed from limestone.
Wet climate: In heavy rainfall areas, such as in Massachusetts, as water passes through
the soil, the basic soil cations including Ca, Mg, and K are gradually leached and replaced
with acid cations like Al and H+
.
Organic matter decay: Decaying of organic matter releases CO2 which reacts with water
to form acids.
Crop management: Harvesting high-yielding forages, such as corn silage or alfalfa which
both contain significant amounts of basic elements i.e. Ca, Mg, and K, has a significant
effect on soil acidity. Much more complex cations are removed by grains as compared to
leaf and stem. Application of ammoniacal nitrogen fertilizer also may influence soil acidity.
What is the significant of soil pH?
Soil pH influences many soil characteristics that are important to its quality.
Characteristics included:
Availability of nutrients to plants: In acidic soils some important nutrients such as
phosphorous, magnesium, and calcium become less available to plants. Moreover, soil pH
affects microorganism activities that are responsible for breaking down organic matter as
well as many chemical reactions that are taking place in the soil. Thus, the availability of
nitrogen, sulfur, and phosphorus to plants will be reduced.
Aluminum and manganese toxicity: Under acidic conditions, Al+++ that normally is firmly
attached to the soil particles begins to dissolve and enters into the soil solution. Small
amounts of Al+++ in the soil solution can prohibit root growth of many plants. Similarly,
high Mn
++ concentration interferes with the growth of aerial parts of plants and therefore,
significantly reduces final yield.…
Pesticide effectiveness: Many pesticides are effective only if soil pH is appropriate. In acid
soils the pesticides may change to an undesirable form, becoming ineffective. Their
degradation in the soil may not happen as expected, and could pose a problem for the
next crop.
Plant diseases: Sometimes, many plant diseases are caused or exacerbated by extremes
of pH, because this makes essential nutrients unavailable to crops or because the soil
itself is unhealthy. For example, chlorosis of leaf vegetables and