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To raise soil pH (make it less acidic), add garden lime — ground limestone — ideally in fall so it has months to react before spring planting. The amount depends on your soil type and how far you need to move the pH: roughly 5 to 10 pounds of ground limestone per 100 square feet raises pH about one point, less in sandy soil, more in clay. Always test the soil first, because adding lime blind can overshoot and cause its own problems. Lime works slowly, so start early and be patient.
Soil pH controls whether plants can actually take up the nutrients present in the soil, so correcting an overly acidic soil often does more good than fertilizing. Below is how much lime to use, which type to choose, when to apply, and how to avoid overcorrecting. Our guidance reflects extension research and gardener consensus rather than first-hand trials, as described in how we rank.
Test before you add anything
The first step is not lime, it is a soil test. Adding lime without knowing your current pH is guesswork that frequently overshoots, and overly alkaline soil is harder to fix than acidic soil.
- A home pH test kit or meter gives a quick reading of where you stand; see how to test soil pH.
- A lab soil test is far more useful for liming, because it reports buffer pH and gives a specific lime recommendation for your soil, taking guesswork out entirely.
- Sample properly — several cores mixed together from across the area, at root depth; see how to collect a soil sample.
Know your target too: most vegetables and lawns want pH 6.0 to 7.0. If your soil is at 5.5, you are aiming to move it up about a point, not to make it strongly alkaline.
How much lime to use
The amount of lime needed depends on both how far you are moving the pH and your soil's texture, because soils differ hugely in how strongly they resist pH change (their buffering capacity).
| Soil type | Lime to raise pH ~1 point (per 100 sq ft) | Notes |
|---|---|---|
| Sandy | 3 to 5 lb | Low buffering; changes pH easily, so use less and re-test |
| Loam | 5 to 8 lb | Moderate buffering |
| Clay or high-organic | 8 to 12+ lb | High buffering; resists change, needs the most lime |
These are general figures. A lab test's specific recommendation beats them every time. When in doubt, apply somewhat less than you think, re-test after a few months, and add more if needed — it is far easier to add lime than to reverse an overcorrection.
Choosing the right type of lime
Not all lime is the same, and the choice affects both speed and what else you add to the soil.
| Type | Speed | Notes |
|---|---|---|
| Calcitic lime (calcium carbonate) | Moderate | Standard choice; adds calcium |
| Dolomitic lime | Moderate | Adds calcium and magnesium; use where soil is low in magnesium |
| Pelletized lime | Faster, easier to spread | Ground fine then pelletized; less dust, more even coverage |
| Hydrated lime | Fast | Caustic and easy to overapply; not recommended for home gardens |
For most gardeners, pelletized calcitic or dolomitic lime is the best balance of effectiveness, ease, and safety. Choose dolomitic if your soil test shows low magnesium; otherwise calcitic avoids piling on excess magnesium.
How to apply lime
Application technique affects how quickly and evenly lime works.
- Apply in fall where possible, so the lime has all winter to dissolve and react before spring.
- Spread evenly with a drop or broadcast spreader for lawns and large areas, or by hand for beds, at the tested rate.
- Work it into the top 4 to 6 inches of soil in beds you are cultivating; lime moves through soil very slowly, so incorporating it speeds results. On established lawns, apply to the surface and water in.
- Water afterward to begin the reaction.
- Do not exceed about 5 pounds per 100 square feet in a single application; if more is needed, split it into two applications a few months apart.
Keep lime and nitrogen fertilizer applications separate by several weeks — applying them together can release ammonia and waste nitrogen.
Wood ash and other alternatives
Lime is the standard, but a couple of alternatives have their place.
- Wood ash raises pH faster than lime and adds potassium and calcium, but is easy to overapply. Use only a light dusting worked in, test before and after, and never use ash from charcoal, painted, or treated wood.
- Ground oyster shell or eggshell raises pH very slowly, adding calcium over a long period; useful as a gentle amendment, not a quick fix.
- Compost tends to buffer soil toward neutral over time and improves structure, though it will not make a large pH change on its own; see how to make compost.
For a large or precise correction, lime remains the most predictable choice.
Why soil pH matters so much
The reason to bother raising pH is nutrient availability. In overly acidic soil (below about 6.0), key nutrients like phosphorus, calcium, and magnesium become chemically locked up and unavailable to plants, while others like aluminum and manganese can reach toxic levels. Correcting pH into the ideal range unlocks nutrients already present, so plants green up and grow better without extra fertilizer.
Acidic soil also suppresses the soil bacteria that break down organic matter and fix nitrogen, so raising pH improves biological activity too. In short, fixing pH first makes everything else you do for the soil work better. To understand a full test report, see how to read a soil test.
Common mistakes to avoid
Liming goes wrong in a few predictable ways.
- Not testing first. Adding lime blind is the top cause of overcorrection into overly alkaline soil.
- Expecting fast results. Lime takes months; apply in fall for spring benefit.
- Applying too much at once. Split large amounts into staged applications and re-test.
- Using hydrated lime carelessly. It is caustic and easy to overshoot; stick to pelletized garden lime.
- Mixing lime with nitrogen fertilizer. Wastes nitrogen as ammonia; separate the applications.
If you overshoot or need to move the other direction, see how to lower soil pH and how to make soil more acidic. Everything else is at the composting and soil hub.