Lime your lawn when a soil test shows pH below 6.0 for most grass types (or below 5.0 for centipedegrass). Apply no more than 50 lb of ground or pelletized lime per 1,000 sq ft in a single application. If the recommendation exceeds 50 lb, split it into two applications — one in spring and one in fall.
Target pH by Grass Type
| Grass species | Optimal soil pH range |
|---|---|
| Kentucky bluegrass | 6.0–7.0 |
| Tall fescue | 5.8–7.0 |
| Perennial ryegrass | 6.0–7.0 |
| Bermudagrass | 5.8–7.0 |
| Zoysiagrass | 5.8–7.0 |
| St. Augustinegrass | 6.5–7.5 |
| Centipedegrass | 5.0–6.0 |
Source: University of Arkansas Extension FSA-6134; Ohio State University Extension fact sheet on lime and home lawn
Most grasses perform well at pH 6.0–7.0. In that range, nitrogen, phosphorus, potassium, and iron are most available to roots. Below pH 5.8, nutrient availability drops and aluminum can reach concentrations that inhibit root growth.
Lime Product Comparison
| Product | Calcium carbonate equivalent | Speed of action | Max rate (lb/1,000 sq ft) | Notes |
|---|---|---|---|---|
| Ground limestone | 70–95% | Slow (months) | 50 | Standard; inexpensive |
| Pelletized limestone | 70–95% | Moderate | 50 | Easy spreader application; dust-free |
| Dolomitic limestone | 70–95% | Slow | 50 | Also supplies magnesium |
| Hydrated lime | 140% | Fast | 20 | Caustic; skin/eye hazard; wear PPE |
| Burned (quicklime) | 180% | Very fast | 10 | Very hazardous; rarely DIY-appropriate |
Source: Ohio State University Extension lime product table
For most homeowners, pelletized limestone is the practical choice: it flows through a standard broadcast spreader without dust, applies evenly, and produces no hazardous exposure. Ground agricultural lime is cheaper but dusty and harder to spread accurately without a belly spreader.
Safety note: Hydrated lime and burned lime are caustic — they can irritate skin, eyes, and lungs on contact. Wear chemical-resistant gloves, eye protection, and a dust respirator if using either product.
How Much Lime to Apply
The exact amount depends on your soil test results. The soil test report will list either:
- Pounds of CaCO3 (calcium carbonate) lime per 1,000 sq ft, or
- A buffer pH value that requires a conversion table
General framework from University of Arkansas (for 1,000 sq ft, CaCO3 basis):
| Soil pH (measured) | Sandy soil | Clay loam |
|---|---|---|
| Below 5.0 | 80–115 lb | 115–138 lb |
| 5.0–5.4 | 57–92 lb | 92–138 lb |
| 5.5–5.7 | 46–69 lb | 69–115 lb |
| 5.8–6.2 | 0 (at optimum) | 0 (at optimum) |
Because no more than 50 lb per 1,000 sq ft should be applied at one time, recommendations above 50 lb are split across multiple applications.
To convert from CaCO3 lime requirement to actual product to apply: Product needed = CaCO3 requirement / (Calcium carbonate equivalent of product / 100)
Example: Soil test recommends 60 lb CaCO3/1,000 sq ft. You have pelletized lime with 90% CCE. Product = 60 / 0.90 = 67 lb product per 1,000 sq ft — split as 50 lb this fall, 17 lb next spring.
When to Apply Lime
Apply lime in fall or spring when:
- Soil is not frozen
- Grass is not wilted or under drought stress
- Rain is expected within a few days to help move lime into the soil
Irrigate immediately after application if no rain is forecast — this washes lime off the grass blades (preventing burn) and begins dissolving the product into the soil.
Ohio State Extension notes that lime applied before core aeration is particularly effective — holes allow lime to reach the root zone faster than surface application alone.
Application Steps
- Get a soil test and confirm your target pH
- Calculate product amount needed per 1,000 sq ft
- Measure your lawn area (use the fertilizer calculator if needed)
- Load a broadcast spreader with pelletized lime
- Apply half in one direction, then the other half perpendicular — for uniform coverage
- Irrigate to wash lime off leaf blades
- Retest soil 3–6 months later
Do not lime and seed on the same day unless the pH is already close to optimal. Lime takes weeks to begin affecting pH; seed planted immediately after heavy liming may not benefit — and if the soil is already near target, over-liming is the greater risk.
Retest soil every 1–2 years to monitor pH changes, especially in regions with high rainfall that accelerates acidification.
What Causes Soil to Acidify
Several natural and management-driven processes lower pH over time:
- Rainfall and irrigation. Water leaches calcium and magnesium from the soil; hydrogen ions replace them on exchange sites, increasing acidity. This happens faster in high-rainfall regions (Southeast, Pacific Northwest) than in drier climates (Great Plains, Southwest).
- Nitrogen fertilizer. Ammonium-based fertilizers (urea, ammonium sulfate) leave behind acidic residues. Turf fertilized heavily with ammonium-nitrogen acidifies faster than unfertilized lawns.
- Decomposing organic matter. Root exudates and thatch breakdown release organic acids.
- Plant root activity. Grasses exchange hydrogen ions into the soil as they take up nutrients.
In the humid Southeast, soil pH can drop 0.3–0.5 units per year in sandy soils under heavy fertilization. In the arid West, pH rarely drops without intervention — alkaline soils there need sulfur, not lime. University of Kentucky Extension AGR-214 notes that the amount of lime required to raise pH depends strongly on clay content: clay soils are more buffered and need more product to shift the same number of pH units.
Buffer pH vs. Soil pH
Soil test reports sometimes list two pH values: soil pH and buffer pH (also called SMP buffer pH or Woodruff buffer pH). They measure different things:
- Soil pH is the active acidity in the soil water — the number most people recognize.
- Buffer pH measures the reserve acidity held on soil particles. Clay and organic matter hold large amounts of reserve acidity, so a clay loam lawn needs more lime than a sandy loam to reach the same soil pH target, even if both read the same current soil pH.
The lab uses buffer pH to calculate the lime requirement automatically. If your report lists a lime recommendation in pounds per 1,000 sq ft, use that number directly. Do not adjust it based on soil pH alone — the lab has already factored in your soil’s buffering capacity.