Take the simple soil test below to find out how healthy your garden soil is, and where you can improve it for a healthier and more productive garden!
Obviously, good soil is key to growing a healthy and productive garden, but how do you know how good your soil is? You can buy soil test kits that test for soil pH as well as other nutrient levels, but healthy soil means more than just having a good N-P-K ratio for growing certain vegetables. There are also a number of simple soil tests you can do yourself, following a simple system developed for farmers and gardeners by a team in Oregon, called the Willamette Valley Soil Quality Guide.
These simple questions will assess more than just nutrient levels – they will also tell you how good your soil is for growing crops based on a number of other factors, no matter what climate zone or area of the country you live in. Keep in mind that you should test your soil on all of these factors – not just one or two – for a complete picture of your soil’s health.
The best time to perform the full soil test is during the spring and early part of the summer, but some tests can also be done throughout the year. You should perform each soil test in several different locations throughout your garden for most accurate results.
Here is the 10-Step soil test, as listed on RodalesOrganicLife.com:
Soil Test #1: Soil Structure + Tilth
When the soil is neither too wet nor too dry, dig a hole 6 to 10 inches deep. Separate an intact section about the size of a soup can and break it apart with your fingers. Determine whether the soil is cloddy, powdery, or granular. Ideally, your soil should be made up of different sized crumbs that will hold their shape under slight pressure. Clods, or aggregates, as soil scientists call them, that break apart only with difficulty mean your soil is too hard and probably needs more organic matter.
Proper levels of organic matter will typically lead to porous soil, which allows the free movement of both water and oxygen, so your plants can develop strong, healthy roots.
Soil Test #2: Compaction
Plunge a wire flag vertically into the soil at different locations. Mark the depth at which the wire bends. The sooner it bends, the more compacted the soil. A foot or more of easily penetrable soil is ideal.
When your soil is too compacted, it can inhibit root growth as well as water availability, and may also keep earthworms and other important soil fauna from moving freely.
Soil Test #3: Workability
You may have already learned about your soil’s workability the last time you got the garden ready for planting. If tilling or digging the soil produces cloddy or platelike clumps, the workability is low…
If your soil doesn’t pass the workability test, it may also fail many of the other tests as well. If your soil is difficult to work, this also means that it is difficult for water, air, and nutrients to reach the roots, and your soil is probably prone to compaction (see above).
Soil Test #4: Soil Organisms
Measure the animal life in your soil by digging down at least 6 inches and peering intently into the hole for about 4 minutes. Tick off the number and species of each organism observed, such as centipedes, earthworms, ground beetles, and spiders. Because most soil organisms spurn daylight, gently probe the soil to unearth the more shy residents. If you count less than 10, your soil does not have enough active players in the food chain.
This soil test may sound a bit strange at first, but the diversity and quantity of living organisms in your soil are one of the best indicators of a healthy, thriving soil ecosystem. Fungi, bacteria, insects, and worms all help to break down plant residues, improve soil texture, and make more nutrients available to your plants.
Soil Test #5: Earthworms
When the soil is not too dry or wet, examine the soil surface for earthworm casts and/or burrows. Then dig out 6 inches of soil and count the number of earthworms squirming on the shovel. Three worms are good; five are better. The absence of worms means the soil does not have enough of the organic matter they feed on. (An exception: If you live in the Southwest, don’t waste your time looking, even if the soil displays other conditions of soil quality. “Earthworm activity is less likely in the desert,” says the University of Arizona’s Walworth. “Worms don’t like hot soil.”)
Although we tested for soil life in the previous test, earthworms deserve their own step because they are so important to your soil health! Not only do they aerate the soil and create tunnels for water to permeate the ground, but earthworm castings contain high levels of healthy soil enzymes, bacteria, organic matter, and nutrients for your plants.
Soil Test #6: Plant Residue
If you’ve grown a cover crop, dig down 6 inches 1 month after turning it into the soil and then look for plant matter. The range of organic material is important to notice here. The presence of recognizable plant parts, as well as plant fibers and darkly colored humus, indicates an ideal rate of decomposition.
Organic matter is the most important part of soil health, but remember that organic matter doesn’t decompose on its own – it requires a whole range of soil organisms and microorganisms to do the work. If you don’t have enough of these in your soil to facilitate decomposition, or if your soil isn’t aerated well enough, plant matter may break down more slowly and have a slightly sour smell similar to fermentation.
Soil Test #7: Plant Vigor
Start this test during the active growing season and look for healthy plant color and size that’s relatively uniform. Overall health and development must be judged for what’s considered normal for your region. One caveat: If you planted late or during a drought, or suffered a pest infestation, results of this test may be unreliable.
Obviously, the health of your plants is a good indicator of the health of your soil – in fact, it’s the best visible sign of good soil that you’ll see above the ground, so pay attention to how good your plants look!
Soil Test #8: Root Development
Use a shovel or hand trowel to dig gently around a selected plant, preferably a weed you won’t miss. Once you’ve reached root depth, pull an annual plant up and check the extent of root development, searching for fine strands with a white healthy appearance. Brown, mushy roots indicate serious drainage problems—and a poor outlook for this year’s harvest. Stunted roots might also indicate disease or the presence of root-gnawing pests…
Roots are another very obvious indicator of soil health and quality. If plant roots don’t look healthy, something’s probably going on with your soil that isn’t good – and it will lead to poor health in your plants above ground as well.
Soil Test #9: Water Infiltration
Take an empty coffee can with the bottom removed and push it into the soil until just 3 inches remain above the surface. Fill the can with water, marking the water height, and then time how long it takes for the water to be absorbed into the soil. Repeat this several times until the rate of absorption slows and your times become consistent. Anything slower than 1/2 to 1 inch per hour is an indication of compacted soil.
Not only is infiltration important for getting water to the roots of your plants, it also helps to prevent problems that can result from runoff and erosion, and helps air move more efficiently through your soil as well.
Soil Test #10: Water Availability
Wait for a soaking rain; then record how long until plants start to show signs of thirst. Results will vary widely by region. The basic lesson is that if plants require more frequent watering than typical for your region, your soil is probably the culprit.
If your soil is not porous enough (see previous test), water may not absorb deeply enough to keep your plants supplied with water between waterings.
So, how did you do?
If your soil didn’t quite measure up to some (or even most) of these tests, don’t worry! There is a simple fix that will improve your soil in almost every aspect listed above, and that is…
If your soil is lacking in aeration, porosity, or crawly critters that indicate soil health, you need to add more organic matter – and not just once, but on a regular basis. Compost, leaves, wood chips (on the surface only), and grass clippings will all help. After a couple of years of ample and regular additions of these materials, repeat the test, and you should see a noticeable difference – both in your soil health and in the health and productivity of your garden crops.
Check out these posts and categories for lots of helpful tips on incorporating more organic matter into your soil: