Rich, nutrient-dense soil is crucial to successful gardening. Signs of healthy soil include plenty of underground animal and plant activity, such as earthworms and fungi. Soil that is rich in organic matter tends to be darker and crumbles off of the roots of plants you pull up. A healthy, spread-out root system is also a sign of good soil. We talked about determining your soil type, now here are eight simple tests to determine your soil’s health.
These tests are part of the Willamette Valley Soil Quality Guide, a system developed for farmers. The expert developers say that it works for gardeners, too! Do all the steps during spring growing season and use different spots in your garden for the best overall picture of your soil’s health.
Soil Organisms
Healthy soil is full of animal life.
- Dig a hole at least 6 inches deep.
- Watch the interior of the hole for 4 minutes.
- Count the number and species of critters you see like spiders, ground beetles & centipedes.
Anything less than 10 means your soil is low on animal life. A strong population of critters keeps down pests and disease, so “the more, the merrier.”
Earthworms
Worms aerate the soil, allowing better circulation. They also eat organic material, so a big worm population means your soil is rich in nutrients.
- Look for earthworm casts or burrows on the surface of damp soil.
- Dig up a chunk of soil 6 inches deep.
- Count the worms you find in the chunk.
- Five is the magic number, but three is still good.
Earthworm benefits go beyond aeration. These friendly critters leave behind secretions that improve tilth, as well as adding organic matter, bacteria, plant nutrients and enzymes via their casts.
Soil Structure/Tilth
Tilth is the condition of tilled soil.
- Dig a 6 – 10-inch deep hole in damp soil.
- Remove a soup can-sized section intact.
- Break it apart
Healthy soil consists of different sized aggregates or chunks that retain their shape when slight pressure is applied. Rich, organic soil has rounder aggregates, allowing water and air to move more easily around plants’ roots. This results in healthier plants.
If the aggregates are difficult to break apart, you have a hard soil problem.
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Workability
If your soil is hard to work or till and you get clods as a result, your soil has low workability. Workable soil is less likely to compact and allows better circulation of water and vital nutrients.
Compaction
This is compressed, hard soil.
- Stick a wire into the soil.
- Mark the depth when the wire bends.
Ideally, the wire will penetrate the soil by at least a foot or more before bending. Compacted soil restricts water and nutrient availability. It also prevents beneficial critters like earthworms from moving around plant roots.
Water Infiltration
Water infiltration is the process by which water reaches plant roots.
- Remove the bottom of a coffee can.
- Push it into the soil, leaving 3 inches above ground.
- Fill the visible portion with water.
- Mark the water height.
- Time how long it takes the soil to absorb the water.
- Repeat until the absorption rate slows and the time to absorption is consistent.
- If slower than ½ – 1 inch per hour, your soil is likely compacted.
Good water infiltration not only gets water to your plants’ root, it helps prevent erosion and runoff. It also improves aeration.
Water Availability
Well-aerated soil is more evaporation resistant and provides plants an adequate water supply between waterings.
- This test must be done after a soaking rain.
- Keep track of how much time passes between the rain and your plants exhibiting signs of thirst. Different regions will have different results.
- If your plants need increased watering frequency over what is usual for your area, your soil is probably compacted.
Root Development
Healthy root systems mean healthy plants and healthy soil.
- Pick a plant to dig up, such as a weed.
- Dig to root depth and pull up the plant.
- Look at the root development.
- White roots with fine strands are healthy, while brown, mushy roots are a sign of drainage issues.
- Short, stunted roots can mean disease or root-eating pests.
Roots depend on healthy soil, air and water to grow. Healthy root systems indicate healthy, well-aerated soil.
These simple tests can save you time and money and help make your gardening season abundantly successful!
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Thank you so much for informing me that if your soil can bend a wire sooner than 1ft dep then your soil will restrict water and nutrients for the roots. I am trying to plan out a yard for my new home, and I definitely want some large trees to give me shade during the heat of the day. It sounds like I should look into custom topsoil blends that will help my plants grow.
Hi Greta! We are so pleased that you found this article helpful. Amending soil for planting is fairly common and knowing your soil type and needs will help you get the best growing environment. Another thing you can do is purchase worms, the earthmovers aka nightcrawlers like to dig deep and they naturally aerate the soil creating room for roots, water, and airflow. You can learn more here https://www.kellogggarden.com/blog/soil/the-importance-of-garden-worms/
This is fantastic and useful information about the garden issue. Thank you fort the suggestion.
When I was a kid my loved to garden. We had a large one every year. He used to say to pay attention after you turn the soil over to what color it turns when it dries out. Is there any truth to that and if so could you give me more detail? Thank you.
Hi Tim, typically, nutrient-rich soil has a dark brown to black color. However, soil color is not the only indicator of soil health, as explained in this article. Your soil color can range based on the minerals and organic matter present in the soil. We have quite a few articles you may find helpful in our soil category https://www.kellogggarden.com/category/blog/soil/ you may find some other helpful articles to look at for soil health. Happy Gardening!
Hi, thank you for the tips! I’m a new gardener and want to try a garden in my home for the first time. The previous owners had a playground set and there was rubber mulch there at one time. I tilled the soil but am wondering if this is not a good place for a garden or is not healthy unless I remove the rubber mulch? Any thoughts? Thank you!
Hi Cheryl, there is evidence that toxic substances can leach from rubber as it degrades, contaminating soil, plants and waterways if you are growing food to be safe we would recommend removing the rubber mulch.