How do you test raised bed drainage efficiency?
Written by
Paul Reynolds
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Testing soil drainage efficiency helps prevent root rot by indicating how quickly water moves through your soil. The trench test is the most effective method for measuring this because it directly measures actual water movement at root depth. I perform this test before each planting season to detect problems early. Plants die when water remains in the soil longer than roots can tolerate.
Digging Standards
- Excavate 10-inch deep hole with vertical sides
- Make diameter 1.5x your shovel width
- Remove all loose debris from hole bottom
- Perform test when soil is moderately dry
Water & Timing
- Fill hole completely with water
- Measure initial drainage start time immediately
- Record minutes until complete drainage
- Repeat test 24 hours later for accuracy
Interpretation Guide
- 4-10 hours: Optimal drainage
- 10-24 hours: Needs soil amendments
- 24+ hours: Requires structural fixes
- Note water pooling patterns during drainage
Effect of Seasonal Factors on Drainage Speed The tests taken in winter run slower than those taken in summer due to the lower temperature. Heavy clay soils show more variations than sandy soils. Always test during your main growing season; otherwise, the results are not relevant. I keep a record of the results in my garden book for the sake of comparison and to see if there is an improvement.
Modify the solutions to suit the test results. For slow drainage, a large amount of sand (30% volume) is to be incorporated here, and a further test is to be conducted after 48 hours. For persistent pools, French drains should be installed. For rapid drainage, use compost amendments to hold the food. I conduct trench tests in conjunction with soil probe tests to provide a comprehensive moisture survey.
Ensure the efficiency of the drainage through annual monitoring and testing at the same location before planting each year. Note rainfall patterns so that they do not affect the results. Upgrade the solutions slowly over time as beds mature. This monitoring ensures that the drainage system evolves in response to the varying soil conditions over time.
Read the full article: 10 Essential Raised Bed Drainage Fixes
