Soil Analysis for Gardeners

From simple DIY tests to more extensive soil analysis, a multitude of resources exist that will boost your vegetable garden’s bounty from one year to the next.


| September/October 2017



field

Determining soil acidity and alkalinity will help you choose what to grow.

Photo by Lorain Ebbett-Rideout

Whether you’re an experienced gardener who wants to learn more about your existing garden plots or a beginner interested in whether your newly dug garden plot will bear fruit, there are several tests you can employ to test your garden soil; some for free or at minimal expense. Even the most costly tests — a full laboratory soil analysis — are surprisingly affordable.

As with most things, you can start with a simple reality check. If you are examining an existing garden plot, what have you grown there successfully? Have you had unexplained difficulties growing certain crops but not others? If your gardening experiences have been mostly positive — with disease, lack of sunlight, or lack of watering attributed to most failures — your garden soil is likely fairly healthy. However, if some (or all) crops will simply not grow, or will not thrive, you may have a soil-related problem.

If you’ve dug a new garden, what was growing there previously will give you some hints of the soil’s fertility. If the site was covered with grasses or otherwise lush, low-lying vegetation, the soil is probably suitable for gardening. If the site was largely barren, perhaps dominated by a few large plants, you can expect some problems. You should observe any prospective garden patch to ensure it receives full sun.

Drainage test

One of the most important elements in suitable garden soil is its drainage. If the soil retains too much water, the roots of plants can rot, and produce will grow poorly there. A simple drainage test, however, will tell you everything you need to know. To perform the test, pick one or more low-lying spots in the garden to test. If the garden is completely level, test the middle. To perform the test, dig a hole 1 foot deep and 6 inches across. Fill the hole with water and let it drain. Then fill the hole with water again. Now that the surrounding soil is saturated with water, measure how long it takes to drain. If the drainage time is less than 4 hours, you can plant most vegetables without problem. In the case of extremely well-drained soil, the water may be gone within minutes. Poor drainage is most often seen in soils with too much clay and not enough sand.

Soil structure

The components of soil can be broken down into three components: clay, sand, and silt. In the right proportions, these combine to make loam — a rich, well-draining type of soil that is optimal for gardens. A very quick method for assessment of your soil structure is to take a handful of moist, although not soaking wet, soil and squeeze it into a ball. If you open your hands and the ball immediately crumbles, your soil is sandy. If it stays in a ball, even when prodded with your finger, the soil has a lot of clay. If the soil remains as a ball, but crumbles relatively easily when prodded with a finger, it is loamy — a nice blend of sand and clay that has the potential to make great garden soil.

The structure of your soil — with regards to the amount of clay, sand, and silt — can be examined in more detail with a Mason jar test. All you need for this is a Mason jar and its lid. To perform the test, take a soil sample and fill a quart-sized Mason jar 1⁄3 to 1⁄2 full. To take the soil sample, scrape away the top inch of soil and dig the soil beneath. If there are any large rocks or large hunks of organic matter (roots from previous crops, for example), remove these. Next, fill the Mason jar with water, leaving about 1⁄2 to 1 inch of air space on top. (Some gardeners add a couple drops of liquid dishwashing detergent to this water — this may help the soil particles separate a bit, but isn’t strictly needed.) Now shake. And when I say shake, I mean seriously shake the contents of the jar for at least 2 minutes. If everything inside the jar does not look uniformly suspended by this point, keep shaking. In order for the test to work, everything in the jar needs to be evenly suspended throughout. Then let the contents settle. With some sandy soils, this may happen within a few hours. For soils with extensive clay and silt, it may take 48 hours. The longer you leave the jar, the more distinct the three layers will be.





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