The Edmond Sun

April 10, 2014

How to avoid soil compaction in your garden

Ray Ridlen
The Edmond Sun

EDMOND — Does it seem like watering your garden is like washing the driveway? Water just seems to run off and not soak in? For good growth, plants must have space in the soil to get air, water and room for roots to grow. Air space, root room and water availability depend largely on the soil structure. This in turn is closely related to the organic matter in the soil and a suitable distribution of mineral particles of different sizes. It is important to keep the soil open and porous, permit excess water to drain away, and air to enter.  Soil also needs to allow water to percolate down to the roots.

Some studies show that as much as 80 percent of plant problems, including moisture stress, as well as low fruit and flower production, can be traced to soil compaction. Some factors that compact soil are beyond our control. Much need raindrops and watering pack surface particles. One of the most common causes of soil compaction is foot traffic. We must work our gardens, harvest fruit and inspect our plants. Every step compacts soil. Keeping unneeded traffic out of our garden reduces soil compaction. A person’s entire weight on an area the size of a foot is a lot of pressure. It can effect roughly the top 6 inches of soil. So soil compaction is inevitable.  

How do we minimize soil compaction? Try to avoid working in your garden when it is wet. Wet soil compacts easier than dry soil.

Design narrow beds, or beds with borders so that you can reach both sides of the bed. Working the bed from outside the bed prevents compaction.

Create paths or place stepping stones to walk on while working beds.

Place a board down when weeding or deadheading.  Stepping on a board spreads out the pressure on the soil thus reducing compaction.

Add lots of compost. Humus adds air spaces between particles creating a sponge-like response from the soil. So it springs back after it is compressed.  

Spread wood, straw, pine needles or compost as a mulch where you step. This layer distributes your weight over a larger area, reducing the depth of the compaction. Mulch also hosts microorganisms and earthworms that help break up compaction and improve soil texture.

These are a few things we can do. Some compaction will correct itself. Mother Nature supplies a crew of workers to help fluff our gardens. They include earthworms, burrowing insects and mammals, as well as microbes that are searching out food in the soil. Critters not only tunnel and dig, they also leave behind their droppings, which add humus. We may not appreciate all these creatures, especially moles and grubs but they actually do a service for our soil. In Oklahoma we have winter temperatures that drop well below freezing and then warm up. Moisture in the soil expands as it freezes and pushes particles apart. We can count on several thaws and refreezes each year. If the soil is dry, watering on warm winter days will help. Be sure and disconnect the hose after watering.

In annual beds we have opportunity to work the soil between plantings. We should work the ground around perennials also. When we spade our garden we can know if our soil is compacted. When our shove digs up big clumps instead of loose soil, it is a sign that our soil is compacted. To minimize soil compaction, follow these practices and watch your step.

RAY RIDLEN is a horticulture/agriculture educator for the Oklahoma County OSU Extension Service. He may be reached at 713-1125.