Potting Mix Method - B
1:1.5 (Volume Extract)
This method is now commonly used in Holland, France and New Zealand for the
analysis of container growing media. This method has been developed for soil-
less media. It should NOT be used for soils.
1. Take several handfuls of medium (potting mix). Add distilled or deionised
water while mixing by hand.
2. The final moisture content should be such that firmly squeezing the mix just
expresses water from it between the fingers. The amount of squeeze is like a
firm handshake. It is neither a limp nor a crushing squeeze. The mix will be
just a little drier than if it had just stopped draining while in a fairly tall pot.
3. Select a straight-sided, screw-top jar of about 400ml capacity.
4. Pour into it 100ml of water. Mark where this comes to. Pour the water out.
5. Fill about 120ml of moist, loose mix into the jar. Firm it gently with the
fingers and by light dumping. Add more mix if the volume is below 100ml, or
take some out if it is above.
6. Add 150ml of distilled or deionised water.
7. Shake 50 times, leave stand for 15 minutes, than shake 50 times again.
8. Measure the Conductivity, Salinity, or pH by dipping the electrodes into the
water.
For the Conductivity and Salinity measurements, make sure the vent-hole in the
side of the electrode cover is submerged under the surface of the solution. It may
be necessary to pour off the liquid from the sample into a smaller container to do
this correctly.
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