Why use this calculator
Soil pH directly affects nutrient availability, microbial activity, and crop growth. Most crops perform best in the pH range of 6.0-7.0, and acidic soils can lock up essential nutrients like phosphorus and calcium. This calculator determines the correct lime application rate based on your soil type, as heavier soils require more lime to achieve the same pH change.
How to use it
Enter your current soil pH from a recent soil test, your target pH, total field area in hectares, and soil type. The calculator provides lime application rates, total quantities, estimated costs, and the number of truck loads required for delivery.
The formula
Lime Per Hectare = Lime Rate (by soil type) x (Target pH - Current pH). Total Lime = Lime/ha x Field Area. Lime rates: sandy 1.5 t/ha, loam 3.0 t/ha, clay 4.5 t/ha, peat 6.0 t/ha per pH unit.
Worked examples
10 hectares of loam soil from pH 5.5 to 6.5
3.0 tonnes/ha, 30 tonnes total, $1,500 cost, 2 truck loads
25 hectares of clay soil from pH 5.0 to 6.5
6.75 tonnes/ha, 168.75 tonnes total, $8,437.50 cost, 7 truck loads
When people use it
- Planning lime applications for newly acquired farmland
- Budgeting for soil amelioration programs
- Scheduling lime deliveries and spreading operations
- Comparing treatment costs across different soil types
Tips
- Apply lime at least 3-6 months before planting to allow it to react with the soil
- Incorporate lime into the top 10-15cm of soil for fastest pH adjustment
- Use fine-grade lime for quicker reaction compared to coarse agricultural lime
- Retest soil pH annually to track progress and plan maintenance applications
Questions people ask
- How long does lime take to change soil pH?
- Fine agricultural lime begins reacting within weeks but full pH adjustment typically takes 6-12 months depending on particle size, soil moisture, and incorporation method. Coarser lime products can take 2-3 years for complete reaction.
- Can I apply too much lime?
- Yes, over-liming can raise pH above optimal levels, causing micronutrient deficiencies (particularly iron, manganese, and zinc). Always base applications on soil test results rather than guessing, and avoid raising pH more than 1 unit per application.
- What type of lime should I use?
- Agricultural limestone (calcium carbonate) is most common. Dolomitic lime provides both calcium and magnesium. Choose based on your soil's magnesium levels. Finer particle sizes react faster but cost more per tonne.