The “Soil Food Web” Paradigm

Healthy soil is built and maintained by a universe of soil organisms. These organisms make up the soil food web and are the key to unlocking fertility in the soil. The soil food web forms the basis of a healthy farm ecosystem. Without them, farmers and gardeners are required to do the extra work of fertilization, pest/weed and disease control. It doesn’t need to be this way. Healthy soil and healthy plants can happen without our endless toil. But this all hinges on a sound understanding of “soil food web science.” Over time, healthy communities of life underground have been devastated as a result of annual tilling, compacted soil, mismanagement of organic matter, and relentless applications of chemical fertilizers and pesticides/herbicides/fungicides. Various farming practices such as no-till, cover cropping, and chemical-free organic farming are all effective ways to support the soil food web. Gardeners and landscapers can utilize similar strategies to promote the vitalizing force of the critters below. However, nothing has been demonstrated to be more effective and important than compost for establishing the vital, regenerative and chemical-free growing power of the soil food web.

From: USDA's "Soil Biology Primer"

From: USDA’s “Soil Biology Primer”

“Viewing the soil as a regenerative living system is one big kick in the pants for anyone who has been taught that NPK fertilization is more relevant than soil biology.” 
-Michael Phillips

“Soil food web” science includes the following components: Sun, water, air, plants and their roots, bacteria, fungi, protozoa, nematodes, micro and macro-arthropods, earthworms etc, humus (decomposed organic matter) and the mineral components of soil – sand, silt, and clay, as well as humans and their management decisions. The web starts with and is governed by plants, who use the energy of the sun to make carbon chains (photosynthesis); much of these carbon compounds are used as root exudates to attract and develop beneficial microbial communities in and around their root system. Exudates are simple sugars, proteins, and carbohydrates released by plant roots to feed and stimulate populations of beneficial microorganism. They do not feed pathogens. (Lowenfels and Lewis 23-24). Understand that the energy going into roots is not only used to build root structure for stability and fertility; in general, about half of a plant’s energy that goes into its roots is released as exudates (Kourik 10). Why do they do this? Because the energy they give away comes back to them many times over.

The strange reality is that while humans garden plants, plants garden microorganisms. They do this because of the crucial role microbes play in the nutrient cycle. Whereas humans are fed by plants, plants are fed by microorganisms. Microbiologists have found that the number of microorganisms in the rhizosphere – a zone immediately around the roots, extending out about a couple of millimeters – is far greater than in the surrounding soil (Ingham, “Living Soil” 2011). What’s more, studies on foliar dynamics have revealed that living leaves produce exudates through their phyllosphere that attract microbes just as roots do through the rhizosphere (Lowenfels and Lewis 25). All this “life” competes for the exudates in the rhizosphere and phyllosphere. At first glance it would seem like the microbes are the ones being fed, but if you look a little deeper things get much more interesting.

“Soil organic matter is the storehouse for the energy and nutrients used by plants and other organisms. Bacteria, fungi, and other soil dwellers transform and release nutrients from organic matter.”
-Dr. Elaine Ingham

Soil life creates soil structure and produces soil nutrients. The activities of its members bind soil particles together into microaggregates as they create air and water pores. The chemical and biological activity in the thin layer of moisture around aggregates convert nutrients into soluble forms that roots can absorb via ion exchange. Unlike applications of fertilizer, soil nutrients in living soil releases slowly over time; they are available when plants need them. As compost, mulch and other organic matter is added to the soil, their nutrients become immobilized in dead bodies and subsequently mineralized (made available to plants) through digestion or decay. The proximity of microbial action in the rhizosphere is what makes mineralized nutrients far more bioavailable than soluble fertilizer forms.

“There must always be a perfect balance between the process of growth and decay. The consequences of this condition are a living soil, abundant crops of good quality, and livestock which possess the bloom of good health”
– Sir Albert Howard

An increasing number of farmers, gardeners and scientists alike are adopting this new paradigm of “living soil.” It’s not like adopting a child or even a family. When you adopt the living soil paradigm you adopt an entire community; in reality, this shift in understanding is an acknowledgment of an entirely new world. It is changing people’s entire relationship with the process of farming, gardening, and scientific study. The time has come to reform our notions of superiority in the web of life. Nature is not an inanimate resource bank awaiting our plunder. It is an ever-evolving dance of mutuality, collaboration, and adaptation. Time has come to see ourselves as part of this dance, not separate from it. Our roles as participants are many. The integrity and health of the niches that we occupy are largely the result of our attitudes and approaches to management.