17 August 2026 · Field Guide

A simple field water infiltration test

Infiltration rate, how quickly water disappears into the soil surface rather than running off it, sits at the centre of both the erosion and the compaction questions covered elsewhere in this series, and it can be measured with equipment that costs almost nothing: an open ended tin can or length of pipe stands in perfectly well for the ring infiltrometers used in more formal soil surveys.

The five steps of a field infiltration test, at a glance.

What you need

An open ended tin can or pipe section, roughly 10 to 15cm in diameter
A rubber mallet or block of wood to drive it into the ground
A jug of water, measured to a known volume
A stopwatch

The steps

Choose a representative spot and clear the surface. Remove any loose litter or vegetation from directly inside where the ring will sit, but avoid disturbing the soil surface itself.
Drive the ring a few centimetres into the ground. Tap it in evenly using the mallet, checking it sits level and that there is no visible gap around the edge where water could escape sideways rather than passing straight down.
Pour a measured volume of water into the ring in one go. Using the same jug volume each time makes results comparable between sample points.
Start the stopwatch as the water is poured, and time how long it takes to fully disappear below the surface. Note the time for the water to infiltrate completely, or, on very slow draining ground, the level remaining after a fixed period such as ten minutes.
Repeat at several points and compare. A single reading tells you about one spot on one day, so repeating the test at a handful of points, ideally including both a compacted looking area such as a gateway and an undisturbed area of the same field, gives a far more useful comparison than one number alone.

Very fast infiltration on bare or light ground can indicate poor water holding capacity, while very slow infiltration, water still sitting after ten or more minutes, usually points to compaction or surface capping. Cross checking a slow infiltration result against a VESS score from the same spot almost always tells the same story from two different angles.

Infiltration rate is one of the more direct, physical measurements a farmer can take of what is happening below the surface, and unlike some of the other tests in this series, it responds relatively quickly to changes in management: a compacted gateway that is aerated or a field moved from continuous set stocking to a rested rotation can show a measurably different infiltration rate within a season or two.

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