Fertile Soil is the Key to Healthy Growth

Gardeners in Colorado are a patient and persistent lot. We must be, growing plants in Colorado can be tedious battling weather and soils difficult to work.

This spring, our landscapes will come to life with new leaves and flowers. Did you know that the soils will also come to life as well? Just as you tend to the garden, you should also tend to the soil. A cup of undisturbed soils have up to 200 billion bacteria, 50 miles of fungal strands and 50,000 small animals (mites etc). Why should we care about these microscopic forms of life?

The soil is a combination of texture, structure, fertility, and microorganisms. Texture is the amount of sand, silt and clay we have. Most of our soils are clay (difficult to work) but this does vary.

Structure is how the soil particles are arranged. An undisturbed soil will have blocky particles whereas a compacted soil particles are flattened into plates. The problem with a “platy” structure is that it does not have enough open pore space for air and water to move. A soil with a good structure will have 50 percent soil, 45 percent open pore space and 5 percent organic matter. The open pore space should be about half water and half air. This arrangement allows for water to percolate and open spaces for roots to grow.

Fertility is made up of sixteen essential elements. The big three include – nitrogen, phosphorous and potassium. Nitrogen is most known for plant growth and making plants green. Nitrogen is limited in our soils. Phosphorous provides energy and is involved in metabolism. Potassium regulates the plant resulting in good stress tolerance.

Micro-organisms and organic matter are the workhorses of soil. Pick up a handful of soil – the “earthy smell” mainly comes from bacteria. Bacteria are the simplest life form in the soil and also the most important. They are your biological rototillers and fertilizer spreaders! Bacteria excrete a sticky substance that actually glues soil particles together increasing porosity or places for air and roots. Bacteria convert organic nutrient sources to forms useable for plants. Fungi are recyclers and food shoppers. Fungi break down dead woody plant parts to be used again by live plants. Some fungi called mycorrhizae form deals with plants. The deal is that the plant will provide a place for the fungi to live and in-turn the fungus will help solubilize nitrogen, phosphorous and water. Nearly all plants form mutualistic deals with fungi. Larger soil microbes, protozoa, nematodes, mites, and earthworms eat the smaller life forms keeping the circle of life in-check.

What can you do to enhance your soil food web?

Organic matter – Add organic matter including compost, humus and organic mulch. These serve as food sources for soil microbes. Organic mulch includes grass clippings, pine needles, and wood chips.

Water – Microbes like moist, but not water logged soils. Too much water drives out the soil oxygen depriving microbes of essential oxygen.

Avoid unnecessary rototilling in the garden. Continual rototilling breaks up soil structure and destroys some of the fungal relationships.

Avoid plastic sheeting under inorganic (rock) mulch. The sheeting reduces soil air and water movement needed for microbial development.