Sulphur pH Lowering Calculator & Acidify Your Soil

It depends on how far you're dropping the pH and your soil texture. As a guide, lowering pH by one unit needs roughly 350 kg/ha of elemental sulphur on sandy soil, 700 on loam and 1,100 on clay (clay buffers more). This tool computes the rate, total and bags from your current and target pH.

Many crops — blueberries, tea, potatoes, azaleas and most acid-loving plants — need acidic soil, and alkaline soils lock up iron, manganese and phosphorus. Elemental sulphur is the standard, cost-effective way to acidify soil; this is the mirror image of using lime to raise pH on acid soils.

Soil bacteria (Thiobacillus) oxidise the sulphur to sulphuric acid, which lowers pH. Because it's a biological process, it's gradual — taking weeks to months and needing warm, moist, aerated soil. That's why you apply sulphur well ahead of the crop, not the day you sow.

Clay and high-organic soils resist pH change (high buffering), so they need much more sulphur than sandy soils for the same drop. The tool uses a texture-specific factor — sandy needs the least, clay the most — so the rate suits your soil rather than a one-size-fits-all number.

Typically a few weeks to several months, depending on soil temperature, moisture, sulphur particle size (finer is faster) and the microbial population. Apply and incorporate it well before planting, keep the soil warm and moist, and re-test pH before relying on the change.

Yes — over-acidifying can drop pH below the crop's range, harm soil life and free up toxic levels of aluminium or manganese. Aim for the crop's target pH, split large requirements over seasons, and re-test rather than dumping a big dose at once. The tool flags strongly alkaline soils for staged treatment.

Elemental sulphur lowers pH (acidifies); gypsum (calcium sulphate) does NOT change pH — it reclaims sodic soils by supplying calcium to displace sodium. Don't use gypsum to acidify, or sulphur to reclaim sodic soil. Use the Gypsum tool for sodic soils and this tool to lower pH.

Broadcast the finely-ground sulphur evenly and incorporate it into the topsoil where the microbes live, ahead of the season. For established acid-loving plants, work it lightly into the surface and mulch. Keep the soil moist so the oxidising bacteria stay active.

Often yes — in alkaline soils, iron, manganese, zinc and phosphorus become more available as pH falls toward neutral/slightly acidic, curing the yellowing (chlorosis) common on high-pH soils. Aim for the pH range your specific crop prefers rather than the lowest possible.

Re-test pH after each season or a few months after applying. Soils naturally drift back toward their parent pH over time (especially calcareous soils), so periodic top-up applications may be needed. Re-run this tool with the new current pH to size the next dose.