Nature’s Pattern to Build Soil

Dr. Carey Reams strongly admonished his students to “see what you look at.” This is valuable advice I try to follow—especially when I am out in nature. I live on an 8-acre plot that was a cornfield as recently as 2003. The next year the land was developed and all the perimeters were planted with rows of shrubs, hybrid poplars, and ash trees. About half the land was left open.

One day while walking the property I observed the grass in the open land away from the trees had very sparce growth. The grass growing between the rows of trees had at least 3 times the growth and many more legume plants. Neither areas were being fertilized, soil moisture was fine, and both areas were getting mowed with clippings left on the ground. Soil tests showed the exact same pattern and yet the grass between the trees was clearly much more productive even with less sunlight. Why? We will come back to this later.

Have you noticed the global movement toward agroforestry? It is small but growing rapidly. I highly recommend J. Russel Smith’s classic book called Tree Crops. What an inspiring man and book. Trees are being used to reclaim deserts, stabilize erosion on steep land, revitalize rural economies, enhance pastures, and efficiently farm the tropics. Trees are an integral part of how nature builds soil.

Last month I presented the work of professor Gilles Lemieux using Ramial Chipped Wood (RCW). We looked at how twigs and small branches have lignin with a much higher proportion of monomers and oligomers and far less complexed polymers. We also looked at how hardwoods (angiosperms) produce a lignin structure that promotes biodiversity above and below ground while conifers (gymnosperms) have a lignin structure that hinders biodiversity. Ultimately Ramial Chipped Wood provides a steady source of endogenous soil energy that powers the microbial system. And it all starts with depolymerization of oligomers carried out by a group of white rot fungal organisms called Basidiomycetes.

What is the composition of wood? This varies by species and the difference between stem wood vs. twigs and small branches. Here are some general ranges excluding moisture.

Cellulose                          38-50%

Hemicellulose                 23-32%

Lignin                                15-30%

Nitrogen                           1-2%

Minerals                           1%

Other Carbons                <1%

When the fungal decomposers depolymerize the lignin 2 things happen; the carbohydrates, cellulose, and hemicellulose are freed up and serve as a food source for soil microbes. This results in a tremendous growth in the size, vigor, and diversity of the microbial community. While the fungal species unlock the energy all the species in the trophic web are benefited and of course, so are the plants.

The second thing that happens is that humic and fulvic acid precursors are created and released into the soil solution. This helps regulate nutrient flow to plants and has many benefits, including stimulating plant growth.

The enzymatic depolymerization of lignin via Basidiomycetes does not destroy the lignin, it just gets it ready for further processing. It is this remaining lignin that deserves our careful scrutiny.

But first it is important to acknowledge and contrast another major biome that has built up fertile soil; grasslands. Grasslands account for about ¼ of the world’s land area. They occupy a unique position. When rainfall is regular and plentiful forests thrive, when rainfall is too little and inconsistent, deserts are the result. Grasslands occupy the middle region between forests and deserts.

Grasses have a unique lignin structure different from conifers or hardwoods in their underlying lignols. When these lignins decompose grasslands can build up a deep fertile soil. But it is fragile and subject to erosion. Even though the soil may be black and have high levels of organic matter the actual humus content is usually quite low. A lot of what is being measured as organic matter is the accumulated char from grassfires going back thousands of years and not true humus.

The soil developed under hardwood forests is much more stable and resistant to erosion and this has everything to do with the lignin structure. Lignin from wood is a very complex molecule. It is very high in energy and is quite resistant to breakdown. Chemically lignins are crosslinked phenolic polymers.

It is lignin and the great variety of polyphenols that are the source material for the creation of humus, humin, humates, humic acid, and fulvic acid. This transformation of organic compounds occurs though synthesis and retrosynthesis via the work of soil biology. Retrosynthesis is the fracturing of complex molecules to produce new ones that are at least as complex using enzymatic systems. This happens when soil has a well-fed and broad community of microbial life. Microbes facilitate enzymatic pathways that create the constituents of brand-new soil if they have enough energy.

The beauty of using Ramial Chipped Wood is that it contains the source materials needed to make brand new soil (lignins and polyphenols) and the energy needed to power the biology. This is why ramial chips should never be composted. Composting is a process where energy is removed from the carbon structures and minerals are consolidated. Compost is actually an organic fertilizer.

Speaking of energy, the highest storage of energy is in the core of the phenols. Can you guess what it is? Aromatic Hydrocarbons! That’s right—the same 6 carbon ring structures found in crude oil also called benzene.

Dr. Reams used to teach is students to mix used motor oil with sawdust and spread it on the land in the fall. He said the carbons and energy will make plants grow like crazy. As proof he pointed out how junkyards with oil spills would cause weeds to grow 6-12 feet high. I was always a little leery of following this because I wasn’t sure if the used oil had heavy metals from the engine or other chemicals from the refinement process that could be detrimental to the soil. I have long thought that unrefined crude oil would be an awesome input for agriculture. And it is natural and organic.

This was later confirmed when I talked to my brother who works in the oil fields. When crude oil is spilled on land the oil and the “contaminated” soil is removed to a waste area and allowed to sit for a period of time. After this it is auctioned off for disposal. Farmers jump at the chance to buy the soil and spread it out on their fields. The result? Plants grow like mad. The same energy of aromatic hydrocarbons is in ramial chips without any concerns of a visit by the EPA.

Let’s review. Nature’s pattern is to build soil through lignin decomposition. The best soils are built under hardwood forests. Pedogenesis is essentially a forestry process.

The decomposition of woody lignins provides energy to the microbial system and the building blocks to create brand new soil. I saw the early stages of this occurring when I compared the grass growing on open land versus the grass growing between rows of trees. The use of ramial chipped wood copies nature’s pattern from forestry and can be used to empower agriculture.