Perlite & Vermiculite are inorganic soil additives commonly used by gardeners. We all add them automatically to potting soil routinely as it is the done thing, but what are they actually for? What do they do? Do they not do the same thing? or are they different?
|APPEARANCE||Perlite is an irregular, white, hard, crumbly, porous material.||Vermiculite is a irregular (worm like), brown/shiny, soft, spongy material.|
|MANUFACTURE||Made by super-heating volcanic hydrous obsidian.||Made by super-heating aluminosilicate.|
|PH||PH 6.5 - 7.0||± PH 7.0|
|COMPOSITION||Silicon Dioxide SiO2.||aluminium, iron oxides, magnesium oxides.|
|MICROBIAL||Inorganic, Sterile.||Inorganic, Sterile.|
|NUTRIENTS||None.||Potassium, Magnesium, Calcium. Able to absorbe nutrients.|
|Honeycomb, hard. Light.||Layered, spongy. Light.|
|WATER DRAINAGE||Good drainage.||Drainage not as good.|
|WATER RETENTION||Water retention not as good. Retains some water. Dries fast.||Good water retention. Soaks up moisture. Slower to dry.|
|AERATING||Good for aeration. Holes in material create airpockets. High air porosity.||Not as good for aeration. Absorbent nature negates aeration. Medium air porosity.|
Add to soil that requires better drainage and lower water retention.
Plant cuttings & propagation.
Add to soils that require more water retention.
Seed germination and seedlings.
|SUITED||Plants that prefer drier roots/soil.||Plants that prefer moist roots/soil.|
We conducted comparative experiments to observe the comparative water handling abilities of Perlite & Vermiculite. 200ml of tap water was added to 200ml of each material to see how the materials interacted with water. Our observations concluded that adding water to both substances did not show any significant swelling of either material. The size of particles for both Perlite and Vermiculite remained constant in the spresence of water. In our particular experiment we observed and found that the amount of water retained by Vermiculite was actually greater than than that of Perlite. We also observe that the drainage of water from Perlite after removing both substances from their water was greater than that of Vermiculite. In other words Perlite retained less water than Vermiculite. We conclude that Vermiculite does not appear to drain off water as well as Perlite. Which ties in with the claim that Vericulite retains moisture in the soil for longer. Perlite dries out quicker.
Perlite & Vermiculite can be added to soils to:
Make the soil lighter
In large enough quantities, they will create air pockets in the soil to improve root development
In large enough quantities, they will improve dense soils to make them less likely to campact
Improve water retention of soils
Retain less water and facillitate good drainage from soil - dries out quicker
facillitate good aeration by trapping air in the soil
Is most suitable for plants that prefer drier soil
Retain more water for longer - slower to dry out
Impart as well as absorbe nutrients
Is best suited for plants that prefer moister soils