LIME REQUIREMENT AND LIMING MATERIALS FOR ACIDIC SOIL

LIME REQUIREMENT FOR ACID SOIL & LIMING MATERIAL

-Rajesh Debnath

LIMING▪ Application of lime.

▪ To neutralise soil acidity and increases activity of soil bacteria.

▪ Oversupply may result in harm to plant life.

▪ Lime is a basic chemical

Beneficaial effects of liming

Crop yield improvementNutrient availability

Improved microbial activityImproved legume fixation

Calcium and magnesium addition

Distinct growth rate on same acid soil upon liming

Lime requirement determination

▪ It is calculated as CALCIUM CARBONATE EQUIVALENT (CCE) - Expression of the acid-neutralizing capacity of a carbonate rock relative to that of pure calcium carbonate

▪ It is expressed as a percentage.

▪ For pure calcite the value is 100%

▪ pure dolomite the value is 108.5%.

▪ Actual CCE of most limestone varies from these percentages due to impurities in the rock,

How to calculate?

Using the soil lime buffer capacity (LBC):

▪ It is the measure of the amount of soil acidity that must be neutralized to raise soil pH by one unit.

LR (mg CaCO3 kg-1) = LBC x (target pH- [initial pH-0.6])

Equilibrium Lime Buffer Capacity (LBCEq)

• LBCEq refers to LBC at equilibrium at five days

• LBC30refers to LBC after 30-minute equilibration

a. Soils with LBC30 ≤ 250 : LBCEq = (3.6709 x LBC30) - 188.25

b. Soils with LBC30 ≥ 250 : LBCEq = LBC30 x 2.90

Lime requirement determination

Based on the methods followed and developed by different scientists following techniques are present for lime requirement determination:

▪ Shoemaker-McLean-Pratt (SMP) Buffer method

▪ Adams-Evans Buffer Method

Shoemaker-McLean-Pratt (SMP) Buffer method

• Was developed for distinctly different soils.• For use with soils that have large lime requirements

and significant reserves of exchangeable Al

▪ 10 mL of SMP buffer + soil-water slurry in 1:2.5 ratio

▪ Shaken in a mechanical shaker for 10 minutes, and let sit for 20 minutes.

▪ Swirl, insert electrodes, and read the pH to the nearest 0.01 pH unit.

▪ Determine lime requirement from soil-buffer pH and calibration data

Adams-Evans Buffer Method

It was designed for soils that are coarse-textured, with low cation exchange capacities and organic matter

contents, and thus low lime requirements

▪ Use the soil sample previously prepared

▪ Add 10 mL of the Adams-Evans buffer solution to the sample

▪ Stir thoroughly with a glass rod, allow to equilibrate for 15 minutes and stir again.

▪ Let stand another 15 minutes.

▪ Prepare a diluted solution of the Adams-Evans buffer by adding 10 mL of distilled water

▪ Check pH. It should read pH 8.00 +/- 0.10. Adjust pH meter to 8.00.

▪ Insert electrodes into soil-buffer slurry and read pH to nearest 0.05 pH units.

▪ Use the soil-buffer pH and calibration to determine lime requirement.

LIMING MATERIAL

A liming material is any compound that is capable of increasing the soil ph by combining with the H+ ions in the

soil solution

Liming Material Quality Parameters

▪ TNV: the percentage of the material that canneutralize acid expressed as CCE of the product.

▪ CCE compares the liming material to pure calcium carbonate (CaCO3)

▪ The rate of reaction of a liming material is determined by the particle sizes of the material

▪ ENV is the fraction of the material’s CCE that will react with soil acidity in the first year of application

▪ The best way to economically compare two lime products is to look at the cost per ton of ENV obtained by dividing the cost per ton of limestone by the ENV

• Total Neutralizing Value (TNV)

Calcium Carbonate Equivalence (CCE)

Fineness

Effective Neutralizing Value (ENV)

• Cost Effective

Effect of finness of the liming material

Thank you

Reference:• McCart, G.D., G.W. Hawkins, and G.R. Epperson. 1970. Lime for Acid Soils, what

to use and how to apply, Extension Division, Virginia Polytechnic Institute and State University Publication 405

• Shoemaker, H. E., E. O. McLean, and P. F. Pratt. 1961. Buffer methods of determining lime requirements of soils with appreciable amounts of extractable aluminum. Soil Sci. Soc. Amer. Proc. 25:274-277.

• J.B. Peters, K.A. Kelling, E.E Schulte. "choosing between liming material." cocommerce (1996): 336-342.

• Adams, F. and C. E. Evans. 1962. A rapid method for measuring lime requirement of red-yellow podzolic soils. Soil Sci. Soc. Amer. Proc. 26:355-357.