Conduct a “perk” test in your yard before planting to test soil drainage.
Almost every garden instruction guide refers to the importance of “well-draining soil.” If water drains (percolates) away from plant roots too quickly, the plants will parch even if they’re getting regular water. And if water doesn’t drain, many plants will drown and rot from the roots up. A percolation test – or perk test – is a great way to measure drainage in your lawn or garden soil.
Here’s how to conduct an easy, DIY soil perk test in your yard.
Soil Percolation Test
Step 1: Dig Hole
Dig a hole at least 12” in diameter by 12” deep, with straight sides. If you’re testing your entire property, dig several holes scattered around your yard, since drainage can vary.
Step 2: Fill Hole with Water
Fill the hole with water, and let it sit overnight. This saturates the soil and helps give a more accurate test reading.
Step 3: Refill Hole with Water
The next day, refill the hole with water.
Step 4: Measure Water Level
Measure the water level by laying a stick, pipe, or other straight edge across the top of the hole, then use a tape measure or yardstick to determine the water level.
Step 5: Measure Drainage Every Hour
Continue to measure the water level every hour until the hole is empty, noting the number of inches the water level drops per hour.
Ideal Soil Drainage
The ideal soil drainage is around 2” per hour, with readings between 1”- 3” generally OK for garden plants that have average drainage needs. If the rate is less than 1” per hour, your drainage is too slow, and you’ll need to improve drainage or choose plants tolerant of wet soil. If drainage is more than 4” per hour, it’s too fast. Drainage problems can be addressed by:
- Incorporate plenty of compost and organic matter into the soil. Organic matter helps heavy clay soil to drain and helps coarse sandy soil to hold moisture, so it’s a win-win no matter what your soil type!
- Choose plants suited to your soil drainage.
- Build raised beds for better control over the soil texture.
If you’ve ever installed a septic system in your yard, you’re probably familiar with soil percolation tests. Professional perk tests are measured in minutes per inch (MPI). To convert your DIY drainage measurement to MPI, divide the time (in minutes) by the distance (in inches) the water level fell. For example, a rate of 2” per hour would correspond to a perk rate of 30 MPI (60 minutes ÷ 2 inches = 30 MPI).
- Soil Drainage (Bartlett Tree Resource Laboratories)
- Drainage Solutions (video)
- Organic Gardening 101 (article)
- How to Make Compost for Your Garden (video)
- Raised Vegetable Bed (video)
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