Market Farming

["Bill Shoemaker" <wshoemak AT inil.com>]

> ...suggests applying 10-40T/a of
> limestone.  Supposedly the 60-100 mesh limestone adds calcium, improves
> tilth and crop quality.  The effects on tilth seem to be similar to that
> of gypsum - breaking of clay clods - decreased crusting.

Limestone is primarily calcium carbonate, usually around 80-90% calcium. Any 
size mesh will add calcium. Mesh size is just a rough indicator of how 
quickly the limestone will have a mass effect on the soil chemistry. It's 
effect is to supply an essential plant nutrient, calcium, and to alter the 
soil pH. It won't have the same effect as gypsum on clay because it doesn't 
have the sulfate ion.

40 tons per acre of limestone is a huge rate. Even 10 tons is high if your 
goal is to amend soil pH. Most farmers will apply 1-2 tons per acre every 
3-4 years. In the Midwest our loamy prairie soils tend to have low pH so 
adding limestone (ag lime) is routine for managing proper soil pH. It comes 
from gravel quarries where they reserve the finer, almost powder-like 
materials for ag lime. Not very complicated really.

Bill Shoemaker, Sr Research Specialist, Food Crops
University of Illinois - St Charles Horticulture Research Center
www.nres.uiuc.edu/faculty/directory/shoemaker_wh.html