Roadside Revegetation

IMPLEMENTATION GUIDES
Table 10.10 | Calcium carbonate equivalents
Liming materials are rated by how well they neutralize the soil using pure limestone as the
baseline of 100 percent. The rating system is called calcium carbonate equivalents (CCE). Values
for some commercially available products are shown below
Material Chemical Formula CCE
Slag CaSiO3 60-90
Agricultural limestones CaCO3 70-90
Marl CaCO3 70-90
Pure limestone CaCO3 100
Pure dolomite CaMg(CO3)2 110
Hydrated lime, slaked lime, builders’ lime Ca(OH)2 120-135
Burned lime, unslaked lime, quicklime CaO 150-175
lime, hydrated lime, or builders lime) and CaO (unslaked lime, burned lime, or quicklime), can
be caustic to germinating seeds and, if used, should be applied several months before sowing
(Havlin and others 1999).
The particle size of the liming material determines how quickly the pH of a soil will increase.
The finer the material, the faster soil pH will increase. For instance, a lime material passing a
100-mesh screen reacts faster and takes less quantity than material passing a 50-mesh screen.
Finer lime materials are more expensive to purchase. If very fine lime is to be used in surface
application, it should meet the following size requirements: 100 percent passing a 100-mesh
sieve and 80 percent to 90 percent passing a 200-mesh sieve.
Determine Liming Rates
Determining how much liming material to apply is based on these factors:
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Soil texture. Soil texture plays an important role in lime requirements because the
higher the clay content, the more lime must be added to the soil. A soil with a clay loam
texture requires over 3 times more lime to raise the pH from 5.0 to 6.0 than a sandy
soil. This is because finer textured soils and organic matter have a higher propensity
to attract and store bases released from liming materials (Inset 10-8).
◾◾
Soil organic matter. Soil organic matter (in humus form) has a high CEC and requires
more lime material to raise the pH.
◾◾
Percentage of rock fragments. Rock fragments have little to no CEC because they are
massive and typically unweathered. Rocky soils will require less lime materials to raise pH.
◾◾
Depth of liming material. Lime materials are relatively insoluble and only change the
pH of the soil around where they were placed. Liming rates are adjusted based on the
soil depth to which the lime material is mixed.
◾◾
Lime material composition. Each liming material is rated by how well it neutralizes
the soil. Less materials with high CCE (see Section 10.1.6.3, Select Liming Materials) are
required as compared to low CCE materials.
◾◾
Fineness of liming material. The fineness of the liming material determines how
quickly the pH will change. Very fine materials change pH quicker than coarse materials.
Inset 10-8 | Cation
exchange capacity (CEC)
The capacity of a soil to hold positive
ions (referred to as bases or cations)
is called the cation exchange capacity
(CEC). A soil with a high CEC holds
a much greater amount of cations,
such as calcium and magnesium,
than a soil with low CEC. For this
reason, a high CEC soil requires
more liming material to raise it to
the same pH level. Cation exchange
capacity is directly related to the
amount of clay and organic matter
present in the soil – the higher the
clay or organic matter content, the
higher the CEC. Rock fragments
have little or no CEC, since they are
massive in structure. Rates of liming
on high coarse fragment soils must
be reduced proportionally.
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
266