Soil Water Solutions


This section lists a number of useful items which I have had to source for my laboratory.

1. Synthetic soil mixes - for use as contact materials, or when minimal chemical reaction is needed from a porous material. Includes how to make a silicate powder tension plate.

2. Moisture Cans - polypropylene and metal. Needed for measuring the water content of soils at 100 degree C

3.. Saran Resin (or alternatives !!) - for coating soil aggregates to measure their volume

4. Pot water controller - to maintain the water content of pots at a fixed suction or water content

5. Transparent Adhesive Scales - for sticking onto glass or clear plastic tubes to convert them to ‘measuring cylinders’

7. Laboratory balances - These balances are VERY low cost but offer precision and reliability equivalent to the ‘name brand’’ balances available to the laboratory and schools market.

8. Tension Plates - for bringing soils to a set moisture potential.

Synthetic soil’ mixes. Sometimes a soil-like porous material which is chemically inert is needed for experimental work.  Soil water solutions stocks (or can get) a large range of glass bead, clay mineral, or silicate based powders which can be mixed to produce specific properties. 

Price depends on the components of the mix - typically $10/kg

Examples : (call with your needs!)

a. Soil water sensor calibration mix.  This material can be wet up to anywhere from 0 to 0.45 cc/cc water content and still remain non-sticky, friable and easily repacked around a sensor. 

b. Tension plate mix. If you need to make a tension plate to wet soils or drain them to 9 kPa (approx field capacity) then all you need is some tubing a plastic box and some of our tension plate mix.


Moisture cans : Small containers with fitted lids which can be placed in an oven at 105 degree C for soil moisture estimation. 

Polypropylene tubs. 

small 43mm diam x 28mm high (holds 30g soil) 50c each

large 43mm diam x 50 mm high (hold 50g soil) 70c each

These tubs usually have similar weights - an order of twice as many as you need will probably yield a set with the same weight within 0.02g .  These tubs absorb a small amount of water 0.1% in air which is lost on drying - for very high precision work they should be pre-dried or kept in a dessicator

Aluminium tubs - these are made to order there is a set up charge of approx $600 then about $8 each. 

We recommend that these be coated with enamel inside to prevent corrosion if alkaline soil is used and there is a compromise between a tight fitting lid and one which does not jam if grit gets into it.

Saran Resin : to water proof soil aggregates so their density can be measured.

The bad news : SARAN is no longer made by Dow Chemical. 

The good news. Ordinary PVA house paint is a good substitute for non swelling soil. Soil Water Solutions has found several good substitutes for difficult soils - call or email for the latest findings

Pot water controller: Watering experimental pots is an onerous and exacting task - especially if the pot must be held close to a fixed water content.  Our answer is to fix the pot at a particular soil water tension.  Just place our pot water controller device in your pot connect it to a water reservoir set below the level of the pot and the water content will be kept constant, drawing water from the reservoir as needed to maintain a fixed soil water suction in the pot.  Controllers are $15 each and operate best with the reservoir 1m - 0.5 m below the pot.


Transparent Plastic adhesive scales: 0-80cm

We use these to apply waterproof scales on the permeameters we sell. They are made with ‘bumper sticker’ technology and are extremely durable. They can be applied to glass or plastic to provide a measurable scale of water levels etc. Price $10 each incl GST  (We have a large number of offcuts with scale from 60cm -80 cm $2 each)

Laboratory Balances.  These balances are made in China for a company in the USA who do not readily sell overseas. So Soil Water Solutions is stocking the most useful of them.

The iM01 A laboratory balance 1000g range x 0.01 g precision with computer communications powered by plug pack or inbuilt SLA battery - $300 GST and recording software included

more information here

Tension Plates : Are used to bring soils to a controlled moisture status.  Soil Water Solutions can now supply plates with air entry value of 40kPa (400cm water suction) ie good for ‘field capacity’ measurements only.  Rectangular plates 35 x 38cm $550 GST incl, or round plates 33cm diam ($450 incl GST)

How to set up a suction plate system- click here

If you have old clogged or leaking tension plates we can refurbish the ceramic to as-new condition and fit it to a new base - or in some cases - refitted to the old base.  NOTE: this work is done on an ‘every care but no responsibility’ basis - ie if we break your plate we won’t charge you, but we will not replace the plate either. approx $500 - I will need to see the plate to give a better quote

Ceramic inserts for Soil Moisture (USA) pressure plates cost over $600 - We dont sell them - try .  But if you have plates which need new rubber backing - we can replace the backing for $150 per plate (NOTE: this is done on an ‘every care but no responsibility’ basis - we sometimes break a plate !)


The square plastic sample holders are also available $1.50 ea (incl GST)

How to set up a suction plate system

To drive suction plates at 100 cm (or less) Connect a bottle as in the picture to the right.  The bottle is a regular 500 ml reagent bottle with the addition of an O ring to help the seal the lid.  Holes in the lid are drilled slightly undersize to ensure a seal. (Nylex PVC tube works OK for a while but gets hard and leaks eventually- silicon tube works better - we can supply this if needed - $15/m).

 Set up a shelf 100-150 cm from the floor and put the plate on it.  Put the bottle up next to the plate to wet the samples, and move it to 100cm below the plate to drain them at 100cm (field capacity) suction.  Leave them until they no longer lose water - usually a few days

NOTE It is not possible to take these plates apart for cleaning - build up of algae can be minimised by putting a few drops of algaecide in the water in the bottle.  Algaecide is readily available from swimming pool suppliers.


To drive suction plates at 300 cm, you could use a bench 300 cm from the floor and a hanging column 300cm long (as above) - but this is rather difficult in most buildings, so you need a means of regulating the suction provided by a pump  - this can be a vacuum pump with a vacuum regulator or (my choice) a 'folded water column'.  The pump can be an (expensive ) vac pump designed for the purpose , an aquarium air pump (for small suctions only) or a compressor from a defunct refrigerator or air conditioner (do the right thing and get it removed by a refrigeration tech to avoid the gas being released) These are not designed for pumping wet air but will give good service for a year or so and cost around $20

See the diagram (right) for folded column design.  This is a set of (preferably transparent) tubes interconnected and connected to a vacuum pump such that air enters the first column is sucked down the first tube and bubbles up through 1m of water.  The air at the top of the first column is therefore regulated at 100cm suction.  This air can then be connected to the second column and sucked through a further 100cm of water - so the air at the top of the second column is regulated at 200cm suction.  A third column gives air at 300 cm etc. 

If the air at the top of the relevant column is connected to the air in the bottle (attached to the suction plate) AND THE BOTTLE KEPT AT THE SAME HEIGHT AS THE PLATE !  Then the suction plate will be at the same suction as the air in the column. 

NOTE if the bottle is lower than the plate then the plate suction will be the sum of the air suction from the column and the suction head created by the difference in plate and bottle height

Bubble TowerSetup-sml