What is the Soil Food Web?

What is the Soil Food Web?

What is soil?

Soil is the top layer surface of the earth’s crust. Soil provides plants, animals, and humans many important life giving services. It supports plants, trees, crops, and millions of organisms that grow from and live in the ground. Most of our food is soil dependent. Even as we talk about this, soil is filtering out pollutants from our environment and our drinking water. This slows down the water flow through the ecosystem and allows it to be filtered before it ends up in the roots of plants, in aquifers and rivers, and our drinking water supplies. Soil lays as the foundation of our roads and buildings. Soil has archeological value in that it also protects and preserves our heritage and culture. 

Soil consists of four major components: water, air, mineral grains, and organic matter. The biggest portion is a mixture of mineral grains from rocks and sediments that are generated by the effects of wind, moisture, and seasonal changes like freezing and thawing. Over hundreds of years, this layer evolves gradually. This mixture gives texture to the soil that can be explained as sand, loam, or clay. 

What is a food web?

A food web is the same type idea as a food chain, except that the food chain is thought of more linearly, while the soil food web operates on the concept that all the components, whether they are doing the consuming or being consumed, tend to have a many to many relationship and is more accurately imagined as a web.

What makes up the Soil Food Web?

soil dwelling microorganisms, also known as soil biota, are what brings the soil to life. There are many types of soil biota. Many help in creating healthy soil and promoting healthy plants, and these are regarded as beneficial. Some can cause major problems for growers, including root rots, molds, blights and mildews, and are deemed pathogenic. Both have a valid and significant position in the natural world’s growth and decay processes.

what is the soil food web

Organic matter is formed by soil organisms from rotted and decomposed vegetation. This is a super thin layer, but an essential one that serves as a glue holding together all four components. The amount of air and water in the soil varies and is based on the capacity to hold water, soil texture, and climate. These elements form a very complex ecosystem that is home to millions of creatures living there.

There is an intimate relationship between microbes and plants in the soil in nature. All plants rely on microorganisms to provide all the nutrients they need to grow, access water, avoid harmful pathogens and pests, and break down contaminants in the soil that could stunt growth. The soil’s microbes benefit from the plant’s released exudates. This relationship produces a living environment that is dynamic and interdependent. Not understanding the consequences of our decisions, we use chemical fertilizers, pesticides and herbicides on plants and soil. What we are actually doing is destroying natures soil system that a whole variety of organisms depend on.

Have We Always Known About The Soil Food Web?

Only few years ago, the phrase “soil food web” had only been used by a handful of people in the country. Now it’s starting to appear constantly, and everyone from gardeners to commercial farmers have seen it enough times to wonder what it means.  Now that we know that plants and animals need water, nutrients, and sunlight, our understanding of the ecology of the soil has also been fundamentally changed. The web seems to be much more complex than I had previously understood. Soil food web theory tells us that the living creatures that are found in soil have a way of navigating and interacting with the environment, and that understanding this helps us understand why the world is looking the way it does today.

Who Discovered The Soil Food Web?

The origins of the idea of the Soil Food Web can be traced back to Corvallis, Oregon and Dr. Elaine R. Ingham, founder of Soil Foodweb, Inc. Soil Food Web refers to the relationships between the wide range of living organisms that make their home both in and above the soil. 

How does the Soil Food Web Work?

The aim is to promote the production of the beneficial biota in the garden and kill as many pathogens as possible. By feeding our garden compost, by enhancing nutritional content, texture, aeration, drainage, and soil tilth, we shift the balance toward the useful soil biota. The soil food web works beautifully when these beneficial biota develop, and our plants, gardens, and fields produce plentiful, highly nutritious bounties. 

It Really is Living Soil

Here is a quick summary of the living organisms that build the soil food web and bring the soil to life.

Bacteria

Our natural soils are full of beneficial as well as pathogenic bacteria. A teaspoon of everyday back yard soil could well contain billions of bacteria. There are a thousand different variations of bacteria, many of which are region-specific. In short, they help water move more quickly through the soil, recycle organic material, and help prevent soil disease. Of the many kinds of bacteria, the nitrogen-fixing bacteria are one of the most important groups. They chow down on humus particles (plant matter), producing a waste material called bacterial manure that introduces to the soil new forms of organic content. Through this bacterial waste material, many plants absorb nutrients most effectively, so you want as much nitrogen-fixing bacteria in the soil as possible.  The more the merrier. The waste products of bacteria and it’s waste materials are also consumed by various soil dwellers of many different types, so in addition to nourishing our plants they feed other organisms in the soil. Growing in soils populated by beneficial bacteria, lawns, flower beds and most vegetables can thrive.

Earthworms 

Worms are one of the most beneficial of the soil’s resident organisms. Unfortunately, many common pesticides and herbicides, including some weed-and-feed lawn products, can easily harm or kill them. Many gardeners appreciate earthworms, realizing that they are the best friends of savvy soil cultivators. Worms blend everything together for us when we layer additives on our soil. The worms tunnel through the heavy soil to allow air to come down to the roots of plants. Their castings facilitate solid root growth and supply many residents of the soil with nourishment. It would be difficult to have an overpopulation of worms, but when worms are few and far between, soils fail quickly.

Fungi 

Many gardeners expect fungi to be bad for the soil, but that is not at all the case Fungi are vital to the health of the soil, and beneficial forms can be found in virtually any soil on the planet. Fungi, like bacteria, reduces organic matter by digestion and excretion of humus to replenish nutrients through the soil’s food web Mycorrhizae is one of the fungi that is best known for sticking to the roots of the plant. There they create a mesh of “rootlets” that feed and pump water and nutrients into the root system of the host plant. They actually increase the roots’ surface area, thus strengthening the nutrient absorption capability of the plant.

Fungi outnumber the bacteria in a healthy woodland soil. This is maintained by the leaves falling from the trees and decomposing on the forest floor. In order to keep these forest soils protected, we must maintain the fungal equilibrium by allowing the leaves to decompose and be recycled into the soil. Often that’s not what happens. Instead we collect and remove for aesthetic reasons, robbing away nutrients that are critical to the soils health. in order to prevent the plants from smothering under the leaves you can shred them and return them as mulch. This will speed the decomposition process. For trees and shrubs, which grow best in a fungi-dominated soil, so turning a forest into a park by replacing understory shrubs with grass usually leads to poor soil and stressed plants and trees.

Arthropods 

These recyclers are another requirement. They feed on bacteria, fungi, and earthworms as well as plant particles. This would include microarthropods— such as very tiny species like mites— and larger creatures like sow bugs, springtails, spiders, and centipedes. The microarthropods feed on debris and promoting access to nitrogen and other nutrients for plants and other soil biota Arthropods also regulate the population levels of other species in the soil, keeping things balanced naturally.

Nematodes 

Nematodes are generally supposed to be pathogenic, just like fungi, but the soil has many beneficial nematodes. Great garden soil contains abundant supply of beneficial nematodes like bacteria, protozoa and other nematodes that feed on many other organisms, including pathogenic ones. Nematodes aid the growth of the root, transmitting vital nutrients to plants through their manure. Instead of promoting healthy root growth, pathogenic nematodes eat tissue from live plants, destroying roots. In healthy soil beneficial nematodes help preserve the dominance  of their pathogenic relatives.

Protozoa  

protozoa are single-celled, soil-dwelling organisms that eat bacteria, keep bad bacteria under control, and produce a nitrogen-rich manure that plants can consume. Protozoa make a good meal for the nematodes and other soil fauna that release nitrogen and other nutrients back into the soil when they excrete their waste.

How do you know if your soil needs regeneration?

We need to recognize that the soil microbiology needs help when disease reaches a point where it affects the plants visibly. The idea is to never let it reach that point. Unfortunately plowing with machinery combined with the chemicals we’ve put in the ground has destroyed most of the networks of bacteria and fungi in our fields. In the case of commercial farms, they’ve literally been poisoned and chopped up with blades of steel season after season.

Natures balance of Good and Bad microorganisms

Many beneficial microbial species can destroy or target harmful bacteria, fungi, or nematodes that attack the root system or plant leaves. The goal is to put the good microbes back in control by reintroducing them to the soil in numbers greater than the bad microbes. Then we let them do their job. Beneficial microbes support the structure of the soil by creating polysacarhides or glues, hyphae strands and tunnels for the soil structure to have air and water. Soil biology restoration is the way to restore soil health and regain a healthy ecosystem and eventually a healthy planet. 

Various plants and animals consume varying nutrient quantities.

To maintain a healthy growth rate, plants need a certain amount of nutrients. Stress from lack of nutrients can arise from a number of causes: plants can be stressed by conditions of drought, mechanical injury or disease. These “microherds” of microbes populate the root zone, called the rhizosphere, of the plant. Most of these are friendly bacteria and fungi; they do not affect living plant tissue and are critical to making sure the plants have access to vital minerals. Such bacteria maintain significant amounts of nitrogen phosphorous, potassium, arsenic, calcium, iron and many other micronutrients in their bodies, thereby preventing the leaching or elimination of these nutrients by water runoff. Ideally, pathogenic species are outnumbered by beneficial species and form a protective barrier on the surface of live plant roots. It is usually only when continuous soil disturbance and harmful chemicals kill the beneficial species of bacteria and fungi that pathogenic species enjoy an advantage and cause problems

The ecosystem needs plants, plants need the ecosystem

The Plants are the real producers in this ecosystem— they use the energy of the sun to convert water and carbon dioxide via photosynthesis into plant material. The main consumers or decomposers, fungi and bacteria in particular, digest dead leaves and other organic matter that falls to the soil surface. Secondary consumers, like protozoa and mites, feast on the fungi and bacteria and excrete nutrients which are plant available, and get absorbed directly by plants. Any undigested leftovers form part of the organic matter of the soil. Larger consumers at a higher level in the food web, like earthworms and ants feast on the secondary consumers. Their fecal matter also becomes part of the soil. It releases nutrients that stimulate the growth of plants.

The active organic matter in the soil is available for the organisms to feed on and decompose into a nutrient-rich humus. There are tons of different types of compounds when it comes to organic matter, some more useful than others. Organic matter is a vital part of the equation that comes in the form of humus. Humus is that which has been reduced to where it can’t decompose or break down any further. 

Excessive turning of the soil in your gardens will increase activity spurts with the bacteria and other organic matter eating organisms but will first eat through active organic matter. Building organic matter and resisting the urge to turn over the soil will increase the active portion of the organic matter which in turn will provide an atmosphere that the species living in the soil will gather around and make their home. Once established they will work hard for you to enhance the soil structure of your gardens.

A healthy food web exists when: 

  1. All the organisms needed by a plant are present and functional.
  2. There is a proper, plant available form of nutrients in the soil that is ideal for plant consumption. Holding nutrients in non-leachable forms that remain in the soil until such time as the plant needs the nutrients is one of the primary functions of a balanced foodweb. At this stage, the plant “turns” the right biology to transform the nutrients into forms that the plant can take up. (these are generally quite leachable) 
  3. The ideal ratio of fungi to bacteria is present, and that the balance between predator and prey is a live, present and active scene. This is is essenial for soil pH, soil structure , and nutrient cycling. In a very healthy soil, all of this decomposition, consumption, digestion, and excretion happens at just the right rate needed to produce the just the right nutrient forms that the plants need.

The functions of a healthy food web are:

  1. Preservation of nutrients so that they do not leach or escape away from the soil as vapor. Retention of the natural nutrients means a reduction in the need for fertilizer. 
  2. At both the right rate and in the right form, the nutrients are cycled throughout the food web. For this to happen, the correct ratio of fungi to bacteria is required, along with a balanced level of natural predator / prey activity. 
  3. Increases in the soil structure to allow oxygen, water and other nutrients to absorb easily and be held by the soil. This allows plants to grow a robust root system that reaches the necessary depth. With properly functioning biology, water usage is decreased, fertilizer requirements are decreased, and plant growth is off the chart. 
  4. Control and suppression of disease-causing species due to natural competition with beneficial entities. This is done by creating soil and foliar conditions that assist the beneficial bacteria as opposed to disease-causing ones. 
  5. Plants enjoy protection of their surfaces, above and below ground. This is done by making sure that foods created by plant surfaces go into the soil and are utilized by beneficial organisms, not disease-causing organisms. This ensures that infection sites on plant surfaces are occupied by beneficial organisms . This also attracts the Predators that prefer to feast on disease-causing organisms. 
  6. Production of hormones and chemicals that promote plant growth that assist in plants developing larger, stronger root systems and therefore more nutrient rich produce. 
  7. Regulation of toxic compounds that are byproducts created as these organic materials break down or decay.

The real value of learning about the soil food web

In one growing season we can rebuild fertility in the soil by working with nature and its processes. Composting methods exist that allow us to attract the right microorganism balance, which is perfect for the type of crops that we want to grow. Many plants need more fungi than others, but there will be bacteria in all soils. Predatory nematodes, micro-arthropods, amoebes and protozoa all need to be present. Larger soil organisms feed on them, and they turn into food for animals such as chickens or moles. The plants could also be food for large animals such as cows, who in turn return nutrient rich manure with nitrogen that feeds the microbes, completing the cycle. This cycle continues in an endless web of interactions, but begins with the assembly of soil microbes.

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