Comparison of Aglime, crushed limestone, G Lime and dolomite
Types of Lime
In WA the main forms of lime are the natural minerals limesand, coastal limestone and dolomite and a chemical byproduct G lime (commonly called burnt lime). Each product is briefly described below:
Limesand
occurs north of Perth, formed from shells and coral particles; high in lime and very fine in its natural state.
Limestone
formed from the limesand particles that have been cemented together over time; typically lower neutralising value and much coarser than limesand.
Dolomite
formed in inland lakes; tends to be variable with clay impurities; typically has a lower neutralising value, is less soluble and much coarser than limesand.
G Lime
a byproduct of quicklime manufacture; contains varying amounts of hydrated lime and calcium carbonate; unstable as the hydrated lime readily reverts to calcium carbonate; typically has a similar neutralising value but contains more coarse particles than limesand.
Quality of Limes
Quality is measured by:
a) Neutralising value
b) Particle size
c) Solubility
a) High NV (90-95%)
b) Fine particles (99%<0.6mm)
c) High solubility
Aglime (limesand) is the most effective liming material available in WA as it has:
University of Western Australia research showed limesand increased soil pH more than G lime and crushed limestone (Speechly 1996).
Note: Rates of lime used in this experiment were adjusted to compensate for differences in neutralising value. See prev research.
Limesand increased canola yields more than either G Lime or dolomite in a field trial harvested in 1997 by Chris Gazey (Agriculture WA).
Adjustments were made to the lime rates to compensate for the lower neutralising value of the dolomite (67%), Both G lime and limesand were applied at 1 and 2 t/ha while dolomite rates were higher - 1.5 and 3.0 t/ha.
The results clearly show that limesand was the superior liming material with dolomite being much less effective even when applied at higher rates.
In fact canola yield increase from 1 t/ha of limesand was more than the yield increase from 3t/ha of dolomite and the same as the yield increase from 2t/ha of G lime.
The high neutralising value, fineness and solubility of Aglime (limesand) makes it the most effective liming material available in WA.
Calcium & Magnesium Bonus
Aglime contains calcium (34%) and magnesium (1.7%) which can supplement low supplies in many soils. Every tonne/ha of Aglime provides around 340kg/ha of calcium and 17kg/ha of magnesium. Trials have proven calcium and magnesium levels increase in plants after applying Aglime. Aglime supplies a good balance of calcium and magnesium as well as being the most effective liming material.
Acknowledgements
Chris Gazey (Agriculture WA)
Andrew Speechly (Student Dept of Soil Science and Plant Nutrition – UWA)
