Addition of finely crushed oyster shells and similar materials to the soil is an ancient
practice, and can be found in the writings of Cato, a Roman era writer. It was well
known that adding such materials to the soil resulted in better crop yields. However, the
reason for this observation was not discovered until the 1800’s, when Edward Ruffin, a
Virginia farmer, correctly reasoned that such practices decreased the acidity of the soil.
Crushed shells and coral sands, if available, are still an acceptable and inexpensive source
of liming material.