Weaving the Soil Food Web

More and more is being discovered every year about the complex relationships that exist in the soil between trees, other plants, fungus, microorganisms, worms and all the other life that exists in the soil. This elaborate set of relationships is known as the soil food web. USDA Soil Food Web Drawing

The Circle of Life

The soil food web is comprised of all the beneficial and parasitic organisms living in your garden, from the birds that eat the earthworms to the bacteria that eat the decomposing roots and other organic matter. All these organisms are affected by each other as they grow, reproduce, and die - whether they are eaten by something bigger, or are decomposed by something smaller. These creatures living in the soil can increase the soil nutrient levels, buffer the pH, and improve the soil quality enough that you may not even need to add any fertilizer at all! The soil food web has additional benefits to your plants beyond soil nutrition, including resistance to certain pests and diseases, better water retention, and insulated soil that decreases summer heat stress and winter freezes.

Feeding Your Soil, Not Your Plants

When selecting and applying fertilizers, the best long-term benefits can be achieved by making decisions to feed and protect the whole soil food web, and not just the plants that you’re cultivating. This is best done with organic fertilizers, whose ingredients provide organic matter, sugars and other nutrients for the creatures living in the soil. Additionally, the fertilizer is in a form that the microorganisms can break down to provide ions for the plants to absorb.

Finally, organic fertilizers have lower concentrations of nutrients than conventional fertilizers; this allows you to improve your soil gradually, which prevents the soil microorganisms from being shocked or killed by the sudden change in the soil chemistry that a higher concentration would cause. redworm for composting Organic matter is perhaps the biggest requirement for a healthy soil food web. The term “organic matter” refers to a mélange of several components. Each plays different roles in the soil. Fresh plant residues or organic materials are un-decomposed plant matter or manure that are incorporated into a compost pile or directly into the soil. These materials initially break down and release nutrients quickly, during which time they are called active organic matter. The microorganisms contributing to the decomposition process are also sometimes counted as part of the organic matter. After the active organic matter has broken down into fully aged compost or humus, it is called stable organic matter. At this point, the rate of decomposition is slow and stabilized, and is in a form that is easier for plants to use.

The Many Benefits of Organic Matter

compost picture Apart from its buffering effects that protect both soil dwellers and plant roots from sudden changes, organic matter provides numerous other benefits to the soil. Organic matter, because of its high Cation Exchange Capacity (CEC) and other structural properties, acts as a reservoir for nutrients and water in the soil. It also contains nutritive components including lignin, starch, protein, and other compounds that feed both the soil dwellers and the plants themselves. These nutrients are released slowly as the organic matter decomposes, providing a long-term food source for plants, animals and microorganisms alike. Organic matter also improves soil structure, making it resistant to compaction and erosion. You can add organic matter by amending your soil with compost, earthworm castings, or fresh plant residues such as a green manure cover crop. To preserve and improve on the organic matter already in your soil, you can reduce or eliminate tillage, reduce erosion with jute netting or cover crops, and fertilize organically to help the microorganisms that create organic matter. However, if your soil food web is weak, adding more organic matter may not be sufficient. Organic matter requires earthworms, mycorrhizal fungi, and other soil dwelling organisms to break it down into useable compounds and ions. You may need to give your soil food web a boost by adding mycorrhizae, earthworm castings containing live eggs, bokashi compost, or another soil inoculant. Organic gardening is about building and maintaining a healthy soil food web. Feed your soil’s helpers, and they’ll feed your plants for you!

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