Soil is the foundation of your garden. It pays to invest in creating the best possible soil for your plants to grow in. Living along the Front Range of Colorado’s Rocky Mountains has many benefits. However, no one would move here for the black topsoil! Instead of the optimal 5% humus content, most of our soils have little or none. It’s up to us to improve on Mother Nature.
You can easily increase the percentage of organic matter in your soil by adding compost or another organic amendment. This added humus will act as a sponge, increasing water retention in sandy soils. On the other hand, in clay it acts to improve drainage by increasing the size of air and water spaces. Plus, organic matter works with your fertilizer by holding nutrients in a form that is available for absorption by roots. As you can see, organic matter is an important component of healthy soil.
It’s best not to add too much organic material at once. Many organic amendments are based on manure, and could contain harmful amounts of salt, as well as weed seeds. Plus, the nitrogen in fresh manure can burn tender roots. Make sure to let manures age before adding them to your garden. Decomposition requires nitrogen. Any form of organic matter that isn’t completely decomposed will steal that essential element from your plants.
Humus doesn’t last forever in the soil. It needs to be renewed. The way nature does this is by covering the bare soil with a layer of mulch. Any material derived from plants—grass clippings, shredded bark, pine needles, etc.—will eventually break down. With annual plants, we use a shovel or tiller to incorporate this decomposing mulch into the soil. But even in permanent plantings, earthworms provide the same service.
If you are amending soil for a vegetable garden, or an annual flower bed, you can build up the organic percentage over several years. In this case, a finely screened compost is ideal, as its small particles won’t get in the way of germinating seeds. Spread a layer about three inches deep over the entire area to be planted, and dig it in a minimum of eight inches deep.
On the other hand, if you’re preparing for a permanent landscape, it’s best to use an amendment that will last longer in the soil. In this case, try using a coarser compost. Renewable Canadian peat moss is a terrific, long lasting amendment, but it’s more expensive. Again, spread a three to four inch layer over the soil and dig it in.
Once you’ve put all that work into amending your soil, it’s important that you avoid walking on it. Digging destroys the soil structure—the way the soil particles are clumped together. Over time, earthworms and pant roots will recreate this structure. In the meantime, it’s critical to avoid compressing the soil particles into a solid mass with no ability to hold air or water. You’ll be doing your roots a favor!
Try creating permanent planting areas with paths around them. Use stepping stones or other hardscape features to gain access to a larger area. Temporarily placing a wide board on the soil gives you a place to stand while spreading your weight out over a larger area.
Properly amending and digging your soil is a lot of work, but you will reap the rewards when you see your plants flourishing.
For more information about choosing an amendment, read the CSU Extention Fact Sheet on that topic.