How to measure water infiltration and interpret results

Water infiltration rates provide information on soil structure. Improved infiltration of rainfall and irrigation water helps to reduce soil erosion and the loss of nutrients from land to water. Find out how to do a simple drainpipe test to assess infiltration into soil.

Use the drainpipe test as a cheap and simple way to measure the infiltration of water into soil. When combined with the spade test, the causes of reduced infiltration (e.g. compaction at depth) can be quickly identified.

This test measures the rate at which water can infiltrate into soil when macropores and micropores are channelling water. It is therefore mainly an indication of the extent of earthworm and old root channels in the soil.

You will need:

• A short length of pipe 10 cm in diameter and 20 cm long
• Hammer
• Stopwatch (often available on your phone)
• 5 litres of water (the same depth of water should be used for each test; 10 cm is suggested)

Step-by-step:

1. Drive the pipe halfway into the ground using a hammer, to leave 10 cm standing above the ground.
2. Pour in water (approximately 800 ml) to a depth of 10 cm.
3. Start the stopwatch immediately and measure the time taken for the water to drain into the soil.
4. Repeat at several locations e.g. in a bed, in a wheeling between beds.
5. After the test, check for any compaction in the soil, e.g. by digging adjacent to the infiltration test.

Drainpipe water infiltration test

The 30-second video below gives a step-by-step demonstration of the infiltration test.

In well-structured soil water moves faster down the soil profile. For soil in good health, the water should drain away within 2 to 5 minutes for light or medium soils. A heavy clay soil with poor structure could take 20 minutes or longer.

The use of organic materials such as compost and green manures can improve soil structure, infiltration and the ability of soil to absorb increasingly intense winter rainfall.