Sampling equipment does not need to be expensive

18th April 2024

… especially when it concerns sampling for (soil) pore water.

If you really want to know what your soil contains, you may well be interested in sampling soil solution; the water which lies in the pores of your sediment.

A very cost effective tool is the Rhizon sampler. These little suction samplers can be inserted in your sediment profile and over some time will ingest the soil water which will be captured either in a sampling tube (much the same as used to take samples of blood) or even simpler, create a negative pressure and capture your sample in a plastic syringe.

There are two sizes available: narrow samplers (+/- 2.5mm) the micro-Rhizon, or the wider samplers (+/- 4mm) the macro-Rhizon. The technology is the same; an inert porous sampling material, available in different lengths. Whereas the micro-Rhizon is best suited to laboratory use, the macro-Rhizon is best for deployment in the field. Over time they will collect up to 10ml resp. 30ml of pore water.

Because the porous polymer is inert, the (water) samples taken by these devices is not altered in any way chemically so it is possible to accurately measure parameters such as pH, Phosphates, Nitrates, macro and micro nutrients.

Perfect for most analytes but there is a word of caution: The pore size of the sampler is 0.15 µm and may therefore be unsuitable for longer stringed compounds such as PAHs or pesticides.

Rhizosphere make connections easy. All samplers are terminated with an industry standard Luer lock; either male or female.

Researchers have sampled soil pore water for many decades. We’ve seen less interest from environmental consultancies, wildlife trusts, water authorities and farmers and we cannot but wonder why that might be. Perhaps because they are too cheap and there is therefore a perception that they can’t possibly be any good?

That certainly would be a great pity because there is no better tool to determine what is really going on close to the plant roots.

Macro and Micro Rhizons are available from Van Walt in pack of 10 units. With prices starting at less than £140 for a pack of 10, this surely represents amazing value for money.

Vincent van Walt

Haslemere, April 2024