What Does Lime Do to Vegetables?

Soil pH

• To understand how lime affects the soil in a vegetable garden, a basic understanding of soil pH is essential. Soil pH is the measure of the alkalinity or acidity of a soil according to the pH scale. Most vegetables favor a pH between 6.0 and 6.8 while pH readings outside of this range mean that plant growth nutrients are be tied up in and bound with soil particles in a form that will not be available for plant uptake. Growers often adjust the pH level of soils in order to make sure that nutrients are available to vegetable plants.

Lime

• Lime in this context usually refers to ground agricultural limestone. Due to limestone's high concentrations of magnesium and calcium, lime raises the pH reading of soils with a pH of 6.0 or lower and lessens its acidity by introducing calcium and magnesium compounds to the soil. For example, adding 3/4 cup of lime and half a cup of 8-8-8 fertilizer can improve soil used for tomato growth. Note, however, that more or less lime may be required by the results of a soil test.

Soil Testing

• Lime is a soil amendment not a soil improver. This is an important distinction because adding lime to a soil that does not need its pH raised does more harm than good. Just as nutrients are bound up in soil particles in soils that are too acidic, the same binding occurs in soils that are not acidic enough. The local extension office performs soil tests and offers advice about using lime to improve the fertility of the soil.

General Liming Considerations

• Generalized recommendations for vegetable garden liming are difficult since liming needs are always primarily considered in light of soil testing. Avoid applying any more than 50 lbs. of lime per 1,000 square feet of vegetable garden space unless your soil is peculiarly acidic. Keeping careful records of every lime addition you make to your vegetable garden soil will help protect against the dangers of over-liming.