Think about liming this fall

Larry Oldham, Extension Soils Specialist
By Larry Oldham, Extension Soils Specialist August 20, 2019 10:46 Updated

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Acid soils will benefit from liming to aid crop growth and development. If a current soil test has a lime recommendation, applying in the fall provides more time for the lime to react with the soil, less management stress, and better field conditions  for equipment operation.

Soil acidity problems rarely have dramatic visual symptoms. Affected areas are less hardy or vigorous in growth; the size of the areas increases within fields over several growing seasons. If lime is needed, the benefits include:

  • preventing aluminum and/or manganese toxicity,
  • increasing phosphorus and molybdenum availability,
  • improving nitrogen fixation by legume crops,
  • improving the efficiency of applied phosphorus and potassium fertilizers, and
  • increasing the volume of soil explored by roots.

Sellers of liming products are subject to the Mississippi Agricultural Liming Materials Act of 1993, and the regulations under that law. Those regulations were amended in 2005 to require a minimum 63% Relative Neutralizing Value (RNV) for hard limes. The RNV “must be shown prominently on the front face of the label, sales invoice, delivery ticket, or bulk ticket”.

Under the Mississippi statute, RNV’s are based on particle size analyses of the lime using the percentage of lime that passes 10-mesh and 50-mesh sieves and the Calcium Carbonate Equivalent data. It is assumed particles larger than 10-mesh are not effective neutralizing soil acidity in an agronomic time frame. All particles smaller than 50-mesh and half the particles in between the two sizes should react.

See for information on how to calculate RNV, and then use that information to compare lime prices.

Is there much difference between lime materials? Several years ago the Mississippi Bureau of Plant Industry collected 20 samples of lime available from Mississippi retailers. Nineteen of the twenty CCE’s were above or near 90, however the RNV values varied about 20% because of the different particle sizes.

See for information about using the Mississippi State University Extension Soil Testing Laboratory for your samples.


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Larry Oldham, Extension Soils Specialist
By Larry Oldham, Extension Soils Specialist August 20, 2019 10:46 Updated
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