Overview
A field trial on how particle size affects lime's ability to lift soil pH
Finer limestone lifts soil pH faster and further than coarse lime, and the trial found no particle size where that stopped being true.
Based on the peer-reviewed paper “Particle Size Determines the Efficiency of Calcitic Limestone in Amending Acidic Soil” by B. J. Scott, M. K. Conyers, R. Fisher and W. Lill, Australian Journal of Agricultural Research (1992). Run by NSW Agriculture at the Agricultural Research Institute, Wagga Wagga, funded by the Wheat Industry Research Committee for N.S.W.
How the trial was set up:
- Calcitic limestone, 98% pure, split into six particle sizes from 3.0 mm down to 5 microns
- Applied at 2.5, 5.0 and 10.0 tonnes per hectare
- Hand spread and incorporated into the soil with a rotary hoe, on land cropped to wheat
- This was cultivated cropping land with lime worked in, not pasture, and not a test of any liquid or surface application
- Soil pH, exchangeable calcium and crop response measured at 6, 12, 24 and 36 months
What they found:
- No minimum particle size was found where lime stopped getting more effective. The finer it went, the bigger the pH and calcium response, right across the range tested
- Most of the pH change happened in the first six months
- Fine particles reacted fast and finished early. Coarse particles kept reacting slowly for years, closing part of the gap but never catching up
- Wheat yield rose with soil pH across all three cropping years
The researchers’ conclusion: finer limestone corrects soil acidity faster and more effectively, but that has to be weighed against the extra cost and handling that comes with grinding lime finer.
👉 Download the full research PDF below to explore the trial data, charts and detailed results.