Why Is Lime Used in Tomatoes?

Lime and pH

• Soil's pH, which refers to its acidity or alkalinity, is an important consideration when you grow any crop. A low reading on the zero-to-14 pH scale indicates acidic soil, while a high pH indicates alkaline soil. A pH of about 7.0 is neutral. Acid soil is a common problem faced by gardeners all over the country, and incorporating lime is the most common way to raise pH.

Soil Acidity for Tomatoes

• Tomatoes, like most garden vegetables, prefer neutral to slightly acidic soil. Their ideal pH is about 6.5 to 6.7. If you are unsure of your soil's pH, a soil test from your nearest university extension office will tell you the pH and recommend whether or not to use lime.

Blossom-end Rot

• Mixing lime in with your soil has another benefit for tomatoes. Lime is primarily composed of calcium carbonate, which helps raise pH by neutralizing acid. Calcium is also beneficial to tomatoes because it can help combat against blossom-end rot, a disorder that causes the fruit to rot starting at the blossom end. Blossom-end rot is caused by calcium deficiency; and lime, along with fertilization, mulching and proper moisture levels, make it less likely to affect your crop.

Considerations

• If tour soil test reveals alkaline soil, do not use lime. While lime can be helpful in acidic soils, in alkaline soils it will only make your soil more alkaline. Alkaline soil is a bit more difficult to fix than acidic soil, but it can usually be amended by incorporating sulfur.