Selecting a liming material – Part 2

A comparison of available liming materials from different sources in Michigan’s Upper Peninsula shows the importance of knowing details about lime and adjusting application rates.

Dumping lime from truck in Ontonagon for MSU trial.

Dumping lime from truck in Ontonagon for MSU trial.

Liming effectiveness varies with proper soil testing, proper lime application rate, even application and proper incorporation. As part of an effort to determine why Michigan’s western Upper Peninsula farmers were not achieving their desired results with lime applications, Michigan State University Extension educators sampled lime from three Upper Peninsula agricultural lime sources and had them analyzed. The following results were obtained.

The “Source A” lime analysis reveals a low moisture lime (good), good neutralizing value, high magnesium content (good if needed, otherwise neutral) and a relatively coarse grind, with only 50.6 percent passing the 60-mesh screen.

The “Source B” lime analysis reveals a higher moisture lime, good neutralizing value, low magnesium and a relatively fine grind (good).

The “Source C” lime is very dry (good), has excellent neutralizing value, high magnesium and a very coarse grind (not so good).

Results of lime analysis in MSU trial

Source

% Neutralizing value

% MgCO3

% Moisture

% passing

8 mesh

60 mesh

100 mesh

A

98.4

39.4

1.4

99.7

50.6

49.7

B

95.4

2.8

13.4

95.6

90.6

75.8

C

103.8

44.9

0

72.7

28.1

27.8

The “effective calcium carbonate” number is a very useful calculation to determine how much of a specific lime should be applied per acre using soil test report recommendations based on a standard ag lime neutralizing value of 90. By assuming a soil test report recommendation of 3 tons of lime per acre and running this calculation on the three samples, three different lime application rates are generated.

Source A

  • <8 mesh = 0.3% x 0 = 0%
  • 8-60 mesh = 49.1% x .5 = 24.5%
  • >60 mesh = 50.6% x 1 = 50.6%
  • 75.1% is the “fineness factor”
  • 75.1% x 98.4 (neutralizing value from analysis) = 74 “effective calcium carbonate”
  • “Correction factor” = 90/74 = 1.2
  • So, 3 tons lime per acre x 1.2 = 3.6 tons lime per acre (moisture in lime is minimal)

Source B

  • <8 mesh = 4.4% x 0 =  0%
  • 8-60 mesh = 5.0% x 0.5 = 2.5%
  • >60 mesh = 90.6% x 1 = 90.6%
  • 93.1% is the “fineness factor”
  • 93.1% x 95.4 (neutralizing value from analysis) = 89 “effective calcium carbonate”
  • “Correction factor” = 90/89 = 1.0 but this lime contains 13.4% moisture by weight
  • So, 3 tons lime per acre x 1.0/0.866 = 3.5 tons lime per acre

Source C

  • <8 mesh = 27.3% x 0 = 0%
  • 8-60 mesh = 44.6% x 0.5 = 22.3%
  • >60 mesh = 28.1% x 1 = 28.1%
  • 50.4% is the “fineness factor”
  • 50.4 x 103.8 (neutralizing value from analysis) = 52 “effective calcium carbonate”
  • “Correction factor” = 90/52 = 1.7
  • So, 3 tons lime per acre x 1.7 = 5.1 tons lime per acre

Does this mean that Source C is the worst choice? Not necessarily. The decision between these three lime sources should include price (lime material and delivery), availability, application equipment needed and timing considerations.

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