Lime Application Calculator
Calculate agricultural lime needed to raise soil pH.
Please note: Planning figures based on published averages. Soil type, climate, variety, season and local practice all shift these results substantially. Base real decisions on a soil test, local extension guidance and the product label — particularly for fertiliser, lime and any crop protection product, where the label is a legal document.
What the Lime Application Calculator does
Lime requirement depends on how far the pH must move and how strongly the soil resists that move. Clay and organic matter buffer heavily, so a clay soil needs about three times the lime a sandy one does for the same pH change — then the product’s neutralising value adjusts for its purity.
Formula
Pure lime = pH change × Lime per pH unit for the textureProduct rate = Pure lime ÷ Neutralising valueTotal = Product rate × Area
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Current soil pH | number | Yes | Accepts 0 or more, up to 14. |
| Target soil pH | number | Yes | Accepts 0 or more, up to 14. |
| Soil texture | one of 5 options | Yes | — |
| Neutralising value of the lime | % | Yes | Pure calcium carbonate is 100%. Most agricultural lime is 85–95%. |
| Area | number | Yes | Accepts more than 0. |
| Area unit | one of 4 options | Yes | — |
| Lime price per tonne | selected currency | Optional | Accepts 0 or more. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Soil texture and Area unit.
- Enter Current soil pH, Target soil pH, Neutralising value of the lime and Area.
- Optionally add Lime price per tonne.
- Select Calculate.
Worked example
Raising a clay soil from pH 5.5 to 6.5 with lime of 90% neutralising value.
- Current
- 5.5
- Target
- 6.5
- Texture
- Clay
- NV
- 90%
Clay needs 4.5 t/ha per pH unit, so 4.5 t/ha as pure carbonate. At 90% NV that becomes 5 t/ha of product.
Reading the result
- "Application advice" is driven purely by the calculated rate — a rate crossing 5 or 7.5 t/ha flips the recommendation, so a small change in target pH near that boundary can change the advice given.
- The "target pH by crop" table is a reference for choosing a sensible target in the first place — the calculator does not itself check the entered target against what any specific crop actually wants.
Assumptions and limitations
- Neutralising value is treated as the product's only quality dimension — the notes flag that fineness also matters for reaction speed, so two products with the same NV but different grinds reach the target pH on very different timelines at the same tonnage.
- The pH-to-lime relationship uses one linear rate per soil texture, which is most accurate for a modest, single-unit shift like the example — real soil buffering is not perfectly linear across the whole pH range.
Common mistakes
- Choosing the wrong soil texture preset for a field that is actually a blend — for example, treating a clay loam as clay — since the rate scales directly with the texture constant, this can mean applying meaningfully more lime than the field needs.
Frequently asked questions
How long does lime take to work?
Six to twelve months for a measurable change and up to two years for the full effect. Finer grades react faster but cost more.
What is neutralising value?
The product’s acid-neutralising power relative to pure calcium carbonate. Lime at 90% NV needs applying at about 11% higher rate than pure material.