How much lime raises soil pH by one point?

Roughly 5 pounds of agricultural lime per 100 square feet raises pH by about one point in loam. Sandy soil needs less (about 3.5 lb) and clay needs more (about 7 lb) because clay buffers pH more strongly. This tool scales to your area and pH gap.

How do I lower soil pH?

Add elemental sulfur. Soil bacteria slowly convert it to sulfuric acid, lowering pH. Roughly 1 to 2 pounds of elemental sulfur per 100 square feet lowers pH by about one point depending on soil texture. The tool gives the sulfur amount when your target is below your current pH.

Why does soil type change the amount?

Clay and high-organic soils resist pH change because they have many sites that hold acidity, called buffering capacity. Sandy soils have little buffering and change quickly. The tool applies lower rates to sand and higher rates to clay to reflect this.

How long until the pH changes?

Lime takes several weeks to months to fully react, and elemental sulfur depends on warm, moist, biologically active soil and can take a full season. Apply and incorporate amendments well before planting, then re-test rather than adding more too soon.

Yes. Over-liming can push pH too high and lock out iron and manganese, while excess sulfur can over-acidify. Change pH in steps of no more than about one point per application, incorporate thoroughly, water in, and re-test before a second round.

Garden Soil pH Amendment Calculator

Most plants take up nutrients best within a specific pH band, so correcting soil pH is a common garden task. This calculator tells you whether to add lime or sulfur, and how much, based on your pH gap, soil texture, and bed area.

How it works

The direction depends on whether you are raising or lowering pH, and the rate depends on soil texture (its buffering capacity). Standard per-100-square-foot, per-pH-point rates are:

RAISE pH with agricultural lime (lb / 100 sqft / pH point):
  sandy 3.5   loam 5.0   clay 7.0

LOWER pH with elemental sulfur (lb / 100 sqft / pH point):
  sandy 1.0   loam 1.5   clay 2.0

amount = rate × |target − current| × (area / 100)

If the target is above current pH the tool recommends lime; if below, sulfur; if equal, no amendment is needed.

Tips and notes

These are practical starting rates, not a substitute for a lab test with a buffer-pH (lime requirement) reading, which is the most accurate guide for heavy soils. Incorporate amendments into the top several inches rather than leaving them on the surface, water them in, and re-test before adding more — both lime and sulfur act slowly. Change pH gradually, no more than about one point per application, to avoid overshooting and locking out micronutrients.