3.4.4. Organic Aspects of Soil

This is the living part of the soil. It includes all organic material and organisms, living or dead, micro or macroscopic. This is the easiest aspect of soil to change and this aspect can change how physical and chemical aspects behave. It will also have a significant impact on the health of your plants.

A visual inspection can tell you a lot about the state of organic matter (“OM”) in your soil. Is there a build up of duff, leaves and partially broken down organic material on the surface? Is it dark in color? Can you see little balls or lumps of organic matter in the soil? Those are called soil aggregates.

These aggregates are a mix of dead bacteria, mucus from worms, and other living things that have become glued together because of those interactions. It indicates live, healthy soils.

When you have sandy soil, this aggregate is additionally your friend because nutrition won’t so easily sink through the sand to wherever it ends up - too often below the plant roots! The aggregates are too big.

These aggregates hold both water and nutrients, living storehouses, so to speak, that continue to support life on many levels. So this is really a desirable outcome of soil building - rich OM with lots of aggregates.

As soil breaks down and if other conditions are right (no disturbance of soil is key), it eventually ends up as a complex combination of living elements that support plant life robustly, and discourage disease and pests.

This dark colored, fluffy, lumpy soil that smells sweet and is producing abundance has good “tilth.” Tilth is the physical condition of soil in relation to its readiness to grow crops. Farmers learn to recognize “good tilth” in any type of soil by its feel and smell. Most people instinctively recognize great soil, especially when they compare it to dead soil in disturbed, toxic, monocropped fields.

There is a lot one can study about soil life and cycles in the soil, like carbon, nitrogen and water cycles, geological history, different kinds of soils, energy exchange vectors, etc, but there are a few points that one can understand without in-depth study or expertise, and have great success.

Diversity is the key to healthy living soils. We regularly use the “kitchen sink” method to build soils and compost piles. We don’t stop there though - we also throw the barn, forest, toilet, and other organic streams at the pile, including animal manure, humanure (carefully and safely handled), weeds, wood chips, seaweed, and anything else we can get our hands on.

Soil science is constantly developing. It is far from settled science. New discoveries are made regularly, some of which appear to contradict earlier ones. Soil scientists will concede that there is more that they don’t know than do know about living soils.

Thus, observing the methods indigenous cultures that have farmed successfully and regeneratively for hundreds or thousands of years has a lot of workability and gives science a great challenge - to find out why it works - not that it works (which it clearly does). The “kitchen sink” method works because we’re offering nature enough diversity of choices that she can sort it out and build the most resilient and regenerative system possible for our ecosystem. This is what she is programmed to do.

Protect organic matter. While minerals may take eons to evolve, organic matter and the nutrition in it are vulnerable to rapid change and loss. Keep your soil covered at all times.

Living soils need moisture, air, protection, and the right diversity of elements in order to thrive and provide everything they have to offer.

Some Elements of Living Soils

Nitrogen fixing bacteria

Living soils are an amazing example of the deeply cooperative aspects of the natural world. Living soils are so good at creating these cooperative, symbiotic relationships, they’ve become a metaphor and inspiration to us in our efforts to build human communities and systems more regeneratively. We can learn so much from nature!

One of these symbiotic relationships happens between certain types of plants (mainly the legume, or pea and bean family) and a bacteria called rhizobium. This bacteria has learned to access the roots of these plants and the sugars the plant produces. In return, the bacteria processes nitrogen that exists in the air and soil that is not bioavailable, and converts it to a version that is available to plants.

These plants are called “nitrogen fixers.” The bacteria is actually what fixes the nitrogen, not the plant. This plant has learned to be a host for this particular bacteria. You can physically see colonies of these bacteria on the roots of these plants (the photo on the right, below).

The process of creating a symbiotic relationship, left. Nitrogen fixing bacteria on roots, right.

More examples of nitrogen fixing bacteria on roots. To some, these nodules might look like a pest like root knot nematodes at first glance, but are very distinctly different from pests on roots.

Root knot nematode damage. Note that roots are deformed and invaded, whereas nitrogen- fixing bacteria are just taking a ride on a healthy root. 
Also note - root knot nematodes don’t do as well in live, healthy soils as they do in depleted sandy soils. More on that later.

When you have a nitrogen fixing plant like beans or pigeon pea, and you chop it down once it’s grown, the roots die back and release the nitrogen into the soil. You can also use the green growth above ground to provide available nitrogen to fruit trees, gardens, etc. This is why soybeans are a good crop to plant with corn, or rotate with corn, though the mainstream methods for accessing nitrogen are not as efficient as the ones we use.

Note: If a nitrogen fixing plant fruits, it does use up a lot of the nitrogen in the energy used to fruit. The best time to cut it down if growing specifically to produce nitrogen for other plants, is before it starts fruiting.

There are many ways that nitrogen is fixed or released in soils. Scientists have found some nitrogen fixing capability in corn, sugar cane, and other crops, though not enough to supply the plant what it needs without external nutrients.

Some of the waste product from living creatures turns into nitrogen. Nitrogen fixing plants still add enough value to the mix to make it worthwhile to have them in the system. We’ll go into this in more depth in following sections, but we want you to understand what this process is and you should be able to recognize nitrogen fixing nodules when you see them.

Nitrogen fixing bacteria in soil are a key part of a regenerative system and can help ensure your plants get the nutrition they need and are productive and healthy. Certain plants, mainly the bean and pea family, can bring lots of these bacteria to the system. Use these plants liberally in your system.

Bacteria

There are numerous types of beneficial bacteria, millions or billions of them within a cubic foot of soil. These bacteria do things like:

Bacteria need food, air, and moisture to survive well; the same thing plant roots and most elements of living soils need.

Other microscopic organisms

Bacteria are the smallest organisms we are generally concerned wtih but there are many others that have similar functions in live soils such as protozoa, amoeba, mites and nematodes. Nematodes are of special interest because many people have dealt with the dreaded root knot nematode that kills plants via their root systems. We saw a photo of that damage above.

Most nematodes are beneficial however.

Microscopic organisms thrive in live, undisturbed soil with plenty of organic matter, and can help plants fight off pests and disease and access nutrition. Create live soils and protect them, and these guys will show up and be on the job helping your plants 24/7.

Fungi, mycelium, and mycorrhizae

Many gardeners and farmers dread “fungus” and think of it as one of the worst disease vectors for their plants. But one of the most exciting discoveries by scientists recently is the relationship of the fungal network to, well, everything, and just how beneficial that relationship can be. There are fungi that set up symbiotic relationships with plant roots in exchange for the sugars created by sunlight and photosynthesis. These fungi can prevent disease fungi from accessing a plant, and can access minerals the plant can’t access and make them bioavailable. They extend filaments throughout the soil - many miles of them - which return nutrients and water to the plant. In essence, they extend the reach of plant roots exponentially. The role fungi plays in this symbiotic relationship is called mycorrhiza. This term denotes the relationship between beneficial fungi and plant roots. Only certain types of fungi are mycorrhizal and develop this relationship with roots.

These fungi connect up with other trees and plants creating a network between plants that act as a communications and nutrient exchange network, called mycelium. This network can extend for hundreds of miles in intact forest systems and produces myriad benefits to the entire ecosystem.

These networks can mean the difference between a plant in a challenging or borderline environment or drought surviving or dying - or producing or not producing.

If you saw the movie Avatar, the mother tree in that film was based on recent research into this area, especially by scientist Susan Simard, who found that mature trees in forests shared not only nutrition through these networks, but information with younger trees, increasing their ability to survive. She also found that different types of trees exchanged benefits across species, and trees formed supportive, interdependent families through these networks.

Mycelium is the part of any fungi that is underground - the aboveground aspect is the mushroom. Mycelium performs a key function of helping break down organic matter to compost. It also has many other interesting properties that can be utilized in green industry, like forming mats. Many products are now being produced by fungi including buildings, dishes, biodegradable packaging and more.

A key food for mycelium is wood and this network especially thrives with oak chips, oak logs and oak leaves. You will almost certainly end up with beneficial fungi networks in your system if you incorporate oak into it, though any tree will support fungi (and different fungi create relationships with different trees).

If you have large, mature trees, a mycorrhizal network is likely already there. This is one reason among many we make every effort to keep older trees in our systems even if they cast a lot of shade. There are many nutritious and delicious plants that thrive under oak, in any case.

Mycelium (fungi) networks are key components in breaking down complex materials like wood, in compost and in forests. Some of them can create a symbiotic relationship with plant roots that can enhance the plant’s access to nutrition and water, and prevent disease. Include woody material like nurse logs or wood chips in your system to encourage these fungi to establish and thrive.

The Soil Food Web

Mycelium are key components in breaking down complex materials like wood, in compost and in forests.

There are many other creatures in the soil, including insects and other visible creatures, that all perform a function in making it easier for plants to survive. This is called the Soil Food Web.