Many people complain about the heavy soils we have in Colorado. Given our dry climate and high clay content, that frustration is understandable. But clay isn’t all bad.

Clay and organic matter are the only parts of soil that hold nutrients. Clay particles are tiny and plate-like, giving them a large surface area where positively charged minerals like calcium, potassium and magnesium can attach. Clay also holds water far better than sand or silt.

Have you ever dug a hole in beach sand and poured water into it? It drains almost immediately. Sandy soil needs to be watered two to three times per day. Compare that to clay, which may take a little effort to saturate but then holds moisture for days. Given the choice, clay has clear advantages.

THE DOWNSIDE OF HEAVY SOIL

To picture soil structure in human scale, imagine sand as exercise balls, silt as basketballs and clay as BBs. A room full of exercise balls would still let in light and air. With basketballs, it’d be dimmer with less oxygen. Fill that same room with BBs and it becomes dense, heavy and nearly impossible to move through. That’s how plant roots experience clay-heavy soil.

Comparison of soils. Credit NESDIS-NOAA

If your soil leans toward clay, adding organic matter will always help. As it breaks down, it creates channels for air and water. 

What doesn’t help is aggressive tilling. Rototilling can turn clay soil into what’s often called “clay flour.” It may look loose at first, but after settling from water, foot traffic and time, it compacts again—often worse than before. While tilling can offer short-term relief, it damages soil structure and creates long-term negative implications for roots.

For a new garden, it’s worth doing the hard work up front and toning down the tillage after that. The first year is your best opportunity to improve the subsoil and incorporate organic matter deep into the profile, bringing multiple layers of soil back to life.

HOW TO IMPROVE IT

Double digging is an effective way to do that. It also helps remove weeds completely, roots and all.

Start at one end of your garden and remove a shovel’s depth of soil, placing it outside the bed. Continue across to form a trench. Then dig a second layer to reach root depth. Loosen the subsoil with a pitchfork or rod, then add compost, old leaves and fertilizer—kelp adds minerals, humic acid improves soil structure and plant vitality, while feather meal and bone meal provide slow-release nutrients that support soil microbes. Then move back one row, filling the trench with soil from the next section. Repeat across the bed, using the soil from the first trench to fill the last.

A broadfork tool is less destructive to soils than rototilling, which can turn clay soil into what’s often called “clay flour”.

In subsequent years, skip the heavy digging. My favorite way to work the soil in the spring is with a broadfork. Its long handles let you use body weight to drive the tines deep into the soil, then gently rock it to open channels without destroying structure, fungi or earthworms. For the hardpan broadfork I like, visit JohnnySeeds.com and search for “727 Hardpan Broadfork.”

At first, you may need to work closely across each row. As the soil improves, you can space out your passes and the broadfork will sink in more easily. You can also spread compost on top and let the broadfork work it in. It’s a great workout without the gas or noise.

FOR BIODYNAMIC GARDENERS: