Soil Acidity and Liming

1
Soil Acidity and Liming

• Dr. Bob Lippert
• Crop and Soil Environmental Science
• Clemson University Extension

2
Causes of Soil Acidity

• Nitrogen fertilization
• Leaching of Ca, Mg and K
• Crop removal of Ca, Mg and K
• Erosion
• Acid rain

3
Acidity from Nitrogen
NH4 2O2 2H NO3- H2O
4
Pounds of CaCO3 to neutralize the acidity from
each pound of N

• Anhydrous ammonia
• Urea
• Ammonium nitrate
• Ammonium sulfate
• Monoammonium phosphate
• Diammonium phosphate

• 1.8
• 1.8
• 1.8
• 5.4
• 5.4
• 3.6

5
Leachability
Aluminum
Calcium
Magnesium
Potassium
Sodium
6
Soil pH and Rainfall
7
Calcium and Magnesium Composition of Monocots
8
Calcium and Magnesium Composition of Dicots
9
Acid Rain
German sandstone statue from 1702 Photographed
in 1908 (left) and 1969 (right)
10
Acid Rain
15 square miles
Sulfur dioxide fumes escaped from a nearby mining
operation and reacted with rain to form sulfuric
acid
11
Erosion
12
Acidity from Organic Matter
O
Organic Matter
C O-
H
13
Acidity from Clean Air!
CO2 H20 HCO3- H
14
Major Benefits of Liming
15
Avoids Aluminum Toxicity
16
Avoids Aluminum Toxicity
17
Lime is an excellent source of Calcium and
Magnesium
18
Optimizes Nutrient Availability
19
Soil pH
20
Soil pH
21
The Buffer pH Measures the Exchangeable and
Active Acidity
22
(No Transcript)
23
Determining Lime Requirement

• Norfolk Cecil
• pH 5.2 pH 5.2
• Buff. pH 7.6 Buff. pH 7.4
• Lime 2 t/ac Lime 3 t/ac

24
Target pHs for High Organic Soils

• If soil organic matter is 5 to 10
• - Lime to pH 5.0 to 5.5
• If soil organic matter is greater than 10
• - Lime to pH 4.7 to 5.0

25
(No Transcript)
26
(No Transcript)
27
Sample Soil Test Report Data
28
Two Considerations with Lime

• Calcium Carbonate Equivalent (CCE), Purity
• Fineness

29
Lime Sources and Their Relative Neutralizing
Values
30
Why doesnt gypsum have any neutralizing value?

• CaSO4 2H20 2H ?
• Ca2 2H SO42- 2H2O
• Note that no H was consumed in this reaction.
• Characteristics of a neutral salt
• It may actually lower soil pH in some special
  situations (long-term effect)
• Applications on soils with high exchangeable
  aluminum (possible phytotoxic short-term effect)

31
Fineness Factor

• 0 effective if retained on an 10-mesh screen
• 50 effective if retained on a 50-mesh screen
• 100 effective if they pass a 50-mesh screen

32
Held on 10 mesh screen (Like gravel) Essentially
0 effective
Through 10 mesh screen 50 effective
Through 50 mesh screen (Like gritty flour) 100
effective
33
Fineness factor

• retained on 10-mesh x 0 effectiveness
• retained on 50-mesh x 50 effectiveness
• passing a 50-mesh x 100 effectiveness

34
If a sample passes the 10-mesh screen and 50 is
retained on the 50-mesh screen its fineness
factor would be 75

• 0 on 10-mesh 0
• 50 retained on 50-mesh x 50 25
• 50 through 50-mesh x 100 50
• 25 50 75

35
The CCE and the fineness factor are multiplied
together to determine the Effective Calcium
Carbonate (ECC)

• CCE 95
• Fineness Factor 75
• ECC 95 x 75 71

36
Effect of Particle Size on Lime Reactivity
37
Effect of Lime Particle Size on pH
Eight tons of lime per acre mixed to 10 inch
depth Initial pH 5.9
1 8 to 16 mesh 2 16 to 30 mesh 3 30 to 50
mesh 4 50 to 100 mesh 5 100 to 200 mesh
38
Effect of Limestone Fineness on Crop Yield
39
Guaranteed Analysis (sample label)
Calcium 18 Cal. Carbonate 48 Magnesium
8 Mag. Carbonate 32 Ca. Carbonate Equiv. 85
10 50 100 90 50 35
Passing Mesh Screen
40
Minimum Screening and CCE Standards

• Screen Mesh for
• Standard Ground
• 10
• 50
• 100

• Minimum Guaranteed
• to Pass
• 90
• 50
• 25

41
Guaranteed Analysis (sample label)
Calcium 18 Cal. Carbonate 48 Magnesium
8 Mag. Carbonate 32 Ca. Carbonate Equiv. 85
10 50 100 90 50 35
Passing Mesh Screen
42
"Dolomitic limestone" means those materials of
which sixteen percent or more of the total
neutralizing value expressed ascalcium carbonate
equivalent is derived from magnesium compounds.
43
Questions