Soil Drainage Test

Last updated: November 20, 2018

What Does Soil Drainage Test Mean?

A soil drainage test, also called a percolation test, or perk test, is used to determine how quickly or slowly water drains from the soil in a particular growing area. This is an important step toward determining how well-drained a particular soil type might be, and whether additives are needed to improve drainage.

Most soil drainage tests involve digging a few holes in the ground, all of even sizes. The holes are then all filled with water, and then the gardener measures the levels using a ruler while keeping an eye on the clock.

Note that a soil drainage test differs from a soil analysis or simple soil test. A soil analysis is done in a lab to determine its nutritional contents, while a simple soil test is done in a jar and is used to determine the texture of the given soil sample.


Maximum Yield Explains Soil Drainage Test

Soil is a crucial consideration for in-ground gardening. However, not all types of soils are created equal. In addition to the level of the various minerals and nutrients found in soil naturally, you also need to consider how much water the soil can retain. Well-drained soil will not hold standing water for long, while poorly-drained soil can hold standing water for long periods.

Ideally, garden soil should hold no standing water, but should be able to retain sufficient moisture to support healthy plant growth. To determine your soil water retention rate, you can perform a simple soil drainage test, or percolation test. This requires nothing more than some basic tools and a shovel.

Dig a hole in the soil that is at least 12 inches by 12 inches. The sides should be straight up and down, not angled. Fill the hole with water and let it sit and drain overnight to saturate the soil. The next day, refill the hole with water and measure the level. You’ll need a straight edge over the top of the hole (you can use a yardstick, pipe or even a stick here), and a tape measure. Continue measuring the level of water in the hole every hour until all of it is gone.

In an ideal situation, water should drain at a rate of two inches per hour. Slightly faster or slower than this is ok, but if it is too much different, you will need to amend the soil using organic matter.


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