Q: I followed your recommendation to get my lawn soil tested. The results say I need to add 90 pounds of lime per 1,000 square feet. Is there a difference in pelletized lime and fast-acting lime?

A: University of Georgia soil scientist Dr. David Kissel says that pelletized lime is made by granulating finely ground limestone.  Most of the products found in Georgia seem to be made of magnesium carbonate. They might be labeled “agricultural lime”. Pelletizing makes them easier to apply using a spreader.

Some fast-acting lime products contain limestone that has been ground to be super fine, so it dissolves in the soil faster. Other  fast-acting lime products are made of calcium carbonate, which dissolves faster than magnesium carbonate.

University soil test results are based on the homeowner using coarse agricultural lime, which has some large particles that react slowly, and some so large that they don’t react at all. This mean you can use less fast-acting lime than the University soil test recommends. Instead of 90 pounds per 1000 square feet, 60 to 65 pounds of the finely ground limestone or calcium carbonate should be sufficient.

Below is a comparison of what percent of each product will pass through varying mesh screens. The higher the mesh size, the smaller the holes. As you can see, 50% of the fast-acting lime passes through a 200 mesh screen but only 20% of regular garden/agricultural powdered lime passes through the same mesh.

Fast-acting lime

Mesh      % passed through
200       50
100       70
60        85
50        90

Powdered lime

200      20
100      40
60      50
50      55

Pelletized lime

100      40
60      50
50      55
40      60