Why lime acid soil?
Most lawn grasses, vegetables and field crops grow best at a soil pH of about 6.0 to 7.0. In acidic soil, nutrients such as phosphorus become less available and aluminum and manganese can reach toxic levels. Lime, ground limestone, neutralizes the acidity and adds calcium, plus magnesium for dolomitic lime.
How the estimate works
The amount of lime needed to raise pH depends strongly on the soil’s buffering capacity: clay and organic soils resist pH change much more than sandy soils. The calculator uses typical extension figures for the amount of pure calcium carbonate needed per unit of pH, by texture, then adjusts for the strength of your product:
Lime needed = (target pH − current pH) × texture factor ÷ (CCE ÷ 100)
The calcium carbonate equivalent (CCE) compares a product with pure calcium carbonate. Ground agricultural lime is often 90% to 100%, hydrated lime about 135% and burnt lime about 180%.
Example
A loam lawn at pH 5.8, target 6.5, with lime of 95% CCE:
- about 53 lb per 1,000 ft²;
- for 5,000 ft², about 264 lb;
- equivalent to about 2,300 lb per acre.
Typical rates to raise pH by one unit
| Soil texture | lb of lime per 1,000 ft² |
|---|---|
| Sand | 30 to 35 |
| Sandy loam | 50 |
| Loam, silt loam | 70 |
| Clay loam | 90 |
| Clay | 110 |
Start with a soil test
A soil test gives the current pH and, from many labs, a buffer pH that leads to a precise lime recommendation. Use it whenever you can: this calculator gives a reasonable estimate, not a prescription.
Applying lime
- On established lawns, apply no more than about 50 lb per 1,000 ft² at once; split larger amounts between spring and fall.
- In gardens, work the lime into the top 6 in of soil.
- Lime reacts slowly: allow 3 to 12 months for the full effect, depending on fineness and moisture. Pelletized lime spreads more easily but reacts at a similar speed.
- Do not apply lime with ammonium fertilizers at the same time.
- Blueberries, azaleas and rhododendrons prefer acidic soil (pH 4.5 to 5.5): do not lime around them.