2.3 Infiltration Rate

Infiltration rate is a good indicator of soil structure and therefore, soil health, as infiltration depends on the level of aggregation (crumb structure) that has formed in the topsoil. Better aggregated (healthy) soils allow water to percolate much faster than poor soils. It can also be an indicator of compaction or thin soils.

The testing area should not be saturated so if it has rained heavily wait until the area is a bit drier!

What to record

Record infiltration rate

Make notes: Anything interesting you’ve noticed!

Photos

Equipment

A smartphone (with Sectormentor downloaded)

150mm x 150mm metal/plastic tubes (with 85mm depth marked)

Water bottle with 450ml marked on it – (this equates to 1″ depth of water when poured into the cylinder)

Water (4L or so – so you can do a few different samples!)

Mallet – for driving tube into soil (optional)

Wood block – to protect from damage when hammering in (optional)

Stopwatch (on phone)

How to do the test

1. Head to the sample location you’re interested in testing, and remove all weeds / debris / vegetation in a 150 x 150 x 150 cm area on the soil.

2. Hammer the infiltration cylinder into the soil, to an 85 mm depth.

3. Gently firm the soil on the inside of the tube, and measure out 450ml of water in your pre-marked bottle.

4. Pour the water into the cylinder and start your timer. Stop the timer when all the water has disappeared into the ground and the surface is just glistening. Record the infiltration time in Sectormentor.

5. Repeat step 4 again in the same location – the second time you get may be a better indication of the actual infiltration rate of your soil (less dependent on recent weather). You may want to keep repeating to see the effect this has on the rate!

6. If you want to work out your infiltration rate in inches/hr. Do 3600/no. of seconds, this gives you the number of inches/hr. If you want to know mm/hr then divide your answer by 25.4.

e.g 20 seconds. Is 3600/20 = 180 inches/hr.

180/25.4 = 7mm/hr