Gillison Pneumatic Elutriator



Elutriation is a process for separating particles based on their size, shape and density. A modified version of a hydropneumatic root elutriator was used to clear seeds from soil samples and to further separate seeds by size on a series of stacked sieves with decreasing mesh sizes. See Gross and Renner (1989) for further information.

Gross, K.L. and K.A. Renner. 1989. A new method for estimating seed numbers in the soil. Weed Science 37:836-839.



Setting up the elutriator

Turn on air until the needle reads across from the black 20. Turn on water to 70 psi. Both these gauges should be checked regularly; during elutriation water should be at 30-40 psi.

Processing samples

Before pouring the soil into the chamber, break up all large clumps of soil and turn on the chamber to allow it to fill halfway with water. Add sample, making sure sieve system is in correct order of (from top to bottom) 710, 425, and 243 at the bottom. Elutriate 0-5 cm samples for 10 minutes and 5-15 samples for 15 minutes. When the sample is done, remove all connecting chamber and sieve systems and rinse through into sieves to make sure nothing is left in the arm. As you take apart the system of sieves and connectors, rinse through each part into the next sieve down. Empty chamber and turn on, allowing it to rinse out for a few seconds.

Filtering samples

243 sieves should always be placed in the large funnels to be rinsed out. For 0-5 cm samples, the 425 and 710 sieves can be placed in smaller funnels unless the sample is unusually large. For 5-15 cm samples, the 425 is placed in a large funnel and the 710 is placed in a small funnel. It helps to wet the filter paper before placing the sieve in the funnel. Rinse off the outside of the sieve and rinse through screen, brushing lightly wit the tip of the water bottle to knock off material that is sticking. Use a spatula to remove all seeds that remain on the inside of the sieve after rinsing. The filter paper is easiest to remove from the funnel with the pump still on. If seeds have slipped down underneath the filter paper, rinse out of funnel onto filter paper. Place filter paper in appropriately labeled petri dish, not fully covering so that the filter paper will not dry and seeds will not germinate. When the filter paper is dry, cover the petri dish and tape securely for storage.


  • Label petri dishes and filter paper ahead of each sample.
  • Use white grease to keep sieves and connectors from sticking together. Avoid getting grease in the mesh on the sieves because it will cause seeds to stick and water to back up.
  • Make sure the chamber you are using has three functioning air jets.
  • The pump should read at 200 or above on the red scale when it is functioning properly. If this is not the case, there could be several causes:1) all connections with hoses should be tight; 2) the rubber stoppers should be pressed into the beakers as tightly as they can be; 3) the switch on the funnel should be in the vertical position when that funnel is on; 4) try to limit the number of funnels you have on at any one time; 5) make sure no water can get into the pump by emptying the beaker out frequently.

Date modified: Tuesday, Oct 24 2023



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