Just a few eons ago, ocean waves lapped against the rocks of Garden of the Gods Park. Rivers flowed out of the mountains, carrying sediment to the shallow inland sea, building deltas. Finer shale and clays settled to the bottom of deeper waters.
Now, gardeners wonder what their soil is like in the Pikes Peak region. You guessed it: we have gravels, sands and clays. We do not have the rich, dark soils built from ancient, decaying forest floors. On the contrary, our soil grossly lacks humus content, and either percolates water too quickly (sand) or hardly at all (clay).
To help gardens in this area succeed, an aggressive soil-amending program may be necessary to make our soils more productive. Healthy soil has many different components to it: minerals, air, water, and microbes.
Last week’s “Dig It” column covered soil testing, which will reveal your soil’s structure and chemical composition. Once you know that, you will know what minerals to add to your soil. The clay and sandy soils of this area generally need only nitrogen added to them.
Traditional fertilizers list the amount of N-P-K in them. This refers to the ratio of nitrogen, phosphorous and potassium only. There are many other things that go into having healthy soil, and Colorado State University strongly encourages gardeners to amend our soils before planting.
Amendments are any material we mix into the soil to improve its physical properties, such as water retention. Mulches are products that are placed on top of the soil, usually to reduce weeds. CSU’s fact sheet on amendments gives more detail, at www.ext.colostate.edu/Pubs/Garden/07235.html.
The goal of using amendments is to provide a better environment for roots, and more balanced nutrition for plants. Compost is an organic amendment that is made from chopped up leaves and other biological material. Compost is one of the best amendments for local soil because it provides nutrients that release slowly, and it improves the soil’s structure. Compost is recommended for both clay and sandy soils.
If you are making your own compost, then you deserve a high-five salute. If you are interested in starting a compost pile, refer to CSU’s Plant Talk publication #1613 and 1614.
When you build healthy soil with compost, you encourage microbial activity in the root zone of your plants, and are likely to invite earthworms to your garden. Earthworks are truly nature’s magical soil engineers!
The best way to mix amendments with your existing soil is to use a mechanical tiller or a sturdy pitchfork combined with sweat. Clay will break into chunks, which increases the pore space for water and air.
Garden centers carry many different kinds of supplements, kelp meal, greensand, humate, dry molasses, alfalfa meal and corn gluten meal. The well-educated employees at our privately-owned garden centers can help you decide which materials might be best for your application. Earthworm castings (poop) have been shown to be one of the most effective fertilizers, as covered in www.ext.colostate.edu/PUBS/columngw/gr070505.html.
If you have plants in your garden already, they will benefit greatly from hand spading some compost into the soil around them. First, remove and gather any existing mulch covering the ground around the plant. Then, carefully loosen the soil a couple of inches deep, without damaging the roots. Dig around the plant as wide as the leaves grow – this is known as the “drip zone.” Mix the dirt, compost, and other amendments in a bucket, and return it to the bed around the plant. Then replace the mulch and water adequately. Your plants will thank you.
Contributed by Ross Krummel, Colorado Master Gardener. For answers to your horticultural questions, contact the Master Gardener Help Desk at 636.8921 or CSUmg2@elpasoco.com (A version of this article appeared in The Gazette on 3/14/09.)