Raising pH with Limestone

The following chart shows the number of pounds of ground limestone (calcium carbonate) needed per 100 square feet to raise soil pH to 6.5. Till this amount into the soil as deeply as possible. Lime moves very slowly in soil. If it is just spread on the surface, it may take years for it to affect the soil a foot deep.

Soil with lots of clay, and soil with a high organic matter content, buffer the pH. This means it takes more lime to change the pH. In soils like these, or if your soil is extremely acid (lower than pH 5.0), it may take a few years of lime treatments to raise your pH to where you want it.

Pounds of Limestone Per 100 Square Feet

Current pH Sandy Loam Loam Clay Loam
4.0 11.5 16 23
4.5 9.5 13.5 19.5
5.0 8 10.5 15
5.5 6 8 10.5
6.0 3 4 5.5