Soil pH is one of the greatest determining factors of whether soil is suitable as a lawn. Soil is considered acidic when is has a pH reading of below 7.0, and alkaline with a reading above 7.0. Turfgrasses used in lawns require an acidity somewhere between 6.0 and 7.0. Lime is used as an amendment to achieve proper acidity when pH is above 7.0.
Soil that has dropped below a reading of 6.0 will not deliver the proper nutrients to lawn grass. Nitrogen, phosphorus, potassium, sulfur, calcium, magnesium and molybdenum is limited in soils this acidic, says Ohio State University. Lime is necessary in organic gardens and severely acidic soil to raise the soil pH.
Lime is usually sold as agricultural lime or ground limestone. There are three major types of limestone types, says West Virginia University: ground limestone, burnt lime and hydrated lime. Ground limestone is pure calcium carbonate. It is the cheapest form of lime. Burnt lime is also called quick or caustic lime. Burnt lime acts quickly and requires half the application. Hydrated lime is also quick to react and requires less application.
A soil test is required before the application of lime, says the University of Missouri Extension. A soil test that measures pH, neutralizable acidity, phosphorus, potassium, calcium, magnesium, organic matter and cation exchange capacity is recommended before establishing a new lawn, every three years on an established lawn or annually when correcting a nutrient deficiency or a pH problem.
Lime is best applied when a lawn is being established. It takes lime two years to move through 2 inches of soil, so mixing the material into the topsoil and subsoil is best. Fall, winter or early spring are the best times to apply lime, although anytime of the year is suitable.
Lime is spread over the entire lawn area. This is essential because lime only moves down through the soil, not horizontally. A lime spreader ensures a thorough application. Lime requirements are assessed according to the pH test. The application limit of lime is 150 lb. per 1,000 square feet. If the soil test indicates that a greater rate is required, half an application is made one year, and the second half the next year.