Living SoilHave you planted the same bed year after year and watched it give back less each time? Does it feel as if the ground has simply given up, and nothing you put in it will grow?
It is a fair question to ask whether soil can die. The research has a more hopeful answer than the word suggests.
Is "dead soil" a real thing?
We looked. No extension page we found defines dead soil, or tired soil, as a term. What the research describes instead is less healthy soil, and it describes it in detail: crusted, compacted, low in organic matter, with few earthworms and roots that cannot go down.
Here is the finding that surprises most gardeners. Extension research says many problems in vegetable gardens, fruit trees, shrubs and flower beds are caused not by pests, diseases or a lack of nutrients, but by poor soil physical conditions. Often the soil is not empty at all. It is squeezed and short of air.
The big idea: soil that grows nothing is usually tired, not dead. Its life is held back by compaction and a lack of organic matter, and both can be changed.
Signs your soil is tired
You can check most of these with a spade and your own senses.
- It cracks. The soil dries and cracks in summer.
- It fights the spade. Digging a hole is difficult, whether the soil is wet or dry.
- Water will not go in. It pools on the surface and drains slowly, or runs off.
- It has a crust. A crust on the surface seals off the pores, holds back seedlings and keeps water out.
- It smells wrong. Soil with enough organic matter has the rich smell of earth. Soil with poor air circulation, a result of reduced organic matter, may smell foul.
- It comes up in clods. Healthy soil has a crumb-like structure and breaks apart easily, leaving no large clods.
- There are no worms. Less healthy soil shows little or no sign of earthworms or their activity.
- Roots turn sideways. In less healthy soil, roots are restricted, with fewer fine roots and roots growing sideways above a compacted layer.
Bare, worn paths, ruts and patches where nothing grows can all point to compaction too.
Two quick tests
For a fair look, dig soil that is moist but not muddy, because dry soil always seems harder. Waiting two to three days after rain or watering is best.
Count the worms. A farm field guide says a healthy soil should have at least 3 earthworms per shovelful, with plenty of casts and channels. That figure comes from farm fields, and no home garden page we found gave a count, so treat it as a rough guide.
Push a wire flag into the ground. If the wire goes in to a depth of 12 inches or more, the soil is considered not compacted. If it starts bending at less than 4 inches, the soil can be considered poor and compacted.
Test the soil as well. One extension source says to hold off on organic matter or fertilizer until a soil test can guide you, and a test rules out pH and nutrients before you blame the structure.
Why compaction hurts soil life
Compacted soil is a poor home for plants and for insects, earthworms and other soil organisms. It also creates airless conditions, and certain disease organisms thrive in them and cause plant disease, especially root rot.
Waterlogging adds its own problem. In saturated soil, extra organic matter may break down without air, and that can produce organic acids that are toxic to plants.
Here is where the sources differ
Should you dig tired soil to loosen it? One extension source says that if you do, the goal is simply to break the soil into small clods, not to pulverize it into dust, which only makes it easier to compact again. Farm research goes further: tilling compacted soil makes it more susceptible to compacting again. And tilling, particularly when the soil is wet, damages its structure and speeds up the loss of organic matter.
One garden source allows a single round of digging: it says to till compost in when a garden is first created, then not in the years after, and to add thin layers of 1 inch to 3 inches of organic mulch or compost to the surface each year instead.
How to restore soil
Feed the life that is already there. Soils naturally contain decomposers, and adding them to the soil or compost pile is not necessary. Most soils already contain mycorrhizal fungi as well. What those organisms need is food: microbes must have a constant supply of organic matter, or their numbers decline.
Organic matter worked into soil helps keep the mineral particles from packing down again, so it keeps the soil porous and draining. Keep your weight off it, too. Dry soil bears weight better than wet soil, so stay off wet ground, and use set paths through beds so the soil around roots is never trodden on.
An inoculant is not a shortcut either. Compacted, flooded or contaminated soil harms mycorrhizal fungi, so an inoculant will not cure a toxic or otherwise unworkable soil.
How long does it take?
No extension page we found gives a recovery time for a garden soil. Building organic matter is slow: one source says it may take a decade or more for levels to rise significantly. The same source says the benefits can be seen after a few additions of organic residues and compost.
As it improves, you should see better crumb, a darker color, more earthworms and more roots.
Where to start
Pick one or two goals for this season rather than trying to fix everything at once. Test the soil, make paths so no one walks on the beds, and add a layer of compost or organic mulch to the surface. Then read how to tell if your soil is healthy and no till gardening and soil compaction.