Grass and Soil; the foundation of civilisation!
There are many who would disagree with the statement that ‘Grass and Soil are the foundation of civilisation’. However, if you took away all the food produced on grassland soils, most of the world’s population would be dead within 2 months, with urban city dwellers being the first victims.
Without the soil, everyone and everything starves (wildlife included). Therefore, it is worth considering what healthy soil is and how it is created or damaged.
What is soil? As defined by Hans Jenny, the ‘Father of Soil Science’, soil is the combination of the parent mineral material (clay, sand, etc. – ‘dirt’), organic matter (carbon compounds), soil biology and an aerobic environment (oxygen present). Put simply, it is dirt plus life. There are more organisms in a double handful of healthy soil than there are humans on earth.
It is also very important to note that plants don’t grow out of soil, soil grows out of plants. If you dry out a plant you find the following composition (on average); Carbon 45% (grasses are often over 50%), Oxygen 45%, Hydrogen 6% and Nitrogen 1.5%. That means that 97.5% of plant matter comes from the air or water. Only 2.5% of a plant comes from base minerals. Essentially, plants take air, water and a small amount of minerals to feed the soil ecosystem that sustains all life on earth. Soil grows from plants, not the other way around.
Which plants build the most soil?
Most people will instinctively answer ‘trees’ and it’s easy to understand why. When you see a tree that is nearly half carbon, you see a lot of biomass.
However, one must consider what you really see when you look at a tree. A tree is tens, hundreds or even thousands of years of stored carbon, none of which is sequestered in soil until the tree dies, falls and decomposes. Even then, much of the dead tree volatilises and returns to the atmosphere. In fact, trees are the slowest builders of topsoil with permanent forests (Boreal, tropical rainforests, etc.) being the slowest of them all. Short lifecycle rhizomic and other deciduous forests (Aspen, Oak, Maple, etc.) store more carbon in soils as they cycle carbon faster (fallen leaves each year and short tree lifecycle).
Consider this; in Brazil, farmers clear thousands of acres of rain forest, burning all the trees. They plant soybeans and after a few years the soil is so degraded they can’t even grow a decent crop with synthetic fertilizers, so they clear more rainforest and move on. Contrast this with the Great Plains of North America where farmers have been beating the soil to death for 150 years and are still able to grow a crop. The organic matter in a forest is above ground in the tree with 50% or less of the tree mass being in the roots, while grasses contain 75-90% of their mass in their root systems. In addition, the above ground biomass of grass is cycled every growing season, sometimes more than once, while the above ground biomass of the tree is cycled every few decades, centuries or millennia.
The grasses, sedges and legumes of a perennial grassland represent the most efficient soil building system on earth. The deepest and richest topsoil on earth is not found under forests, but under perennial grasslands.
Trees, shrubs and grasses all store organic matter and build soil, but grasses are most efficient, shrubs less so and trees the least efficient. The world’s richest topsoil was produced during the Miocene, when most of the world’s grasslands expanded, replacing forests.
How is soil built?
Soil creation starts when a plant is stressed. Stress can come in the form of grazing, mowing or other disturbance (hail, trampling, winter, etc.). In a healthy grassland ecosystem, the natural stressor is grazing and trampling by large herds of migratory ruminant herbivores.
Every time a grass plant is grazed, it pumps carbon, in the form of root exudates, into the soil to stimulate the microorganisms that deliver nutrients to the plant for regrowth. Root exudates are mostly simple sugars plus a small amount of carbohydrates and proteins, essentially ‘root cookies’ (sugar, carbohydrate (flour) and protein (egg)). Bacteria and fungi use this flush of ‘root cookies’ to multiply rapidly. While they do, they produce the enzymes and acids needed to break down parent materials (clay, sand, rock) to release nutrients essential to the plant.
The bacteria excrete a glue to stick themselves to the plant roots, organic material or parent material. This holds them in place so water infiltrating the soil doesn’t wash them away from their food source. This glue begins the formation of micro-aggregates, the beginning of soil structure. Then the fungi release glomalin, another biological glue, which glues these micro-aggregates into macro-aggregates. These soil particles stick together and the pores between them become the pathway for air and water infiltration, traffic of microorganisms, fungal hyphae (like roots) and plant roots.
When this explosion of microbial life takes off, a bunch of predators arrives to enjoy the bounty. Protozoa and micro-arthropods tuck into a banquet of bacteria while fungal and bacteria feeding nematodes tuck into both bacteria and fungi. Earthworms also consume both. In the process of eating all this bacterial and fungal growth, these predators release the mineral based trace nutrients into the soil next to the plant root. The sugars and carbohydrates end up in the soil as soil organic matter. Carbon once in the atmosphere is now stored in soil.
The 'Soil Food Web' is a complex system that sustains all complex terrestrial life on earth.
The plant root then sucks up the nutrients and kicks off the regrowth of leafy above ground vegetation, using photosynthesis to turn CO2 into carbohydrates and oxygen. The oxygen is released into the atmosphere and the carbohydrates are transferred into the root system, priming it for the next grazing or for winter dormancy.
As this cycle repeats over time, soil organic matter begins to build up. As it builds, it can support an increasingly diverse range of soil biology which, in turn, adds to the soil building process. When soil organic matter exceeds 3%, a soil becomes ‘healthy’, supporting a natural soil ecosystem. Somewhere around 4% some additional magic is added with the arrival of methanotrophs, bacteria and archaea that metabolise methane (CH4) as their only source of carbon and energy.
Every 1% organic matter in 12” of topsoil equals around 45,000 gallons, per acre, of additional water storage capacity. Every increase in soil organic matter contributes to a more efficient hydrological cycle, making the ecosystem more drought resistant and helps stabilise water flow to streams and rivers.
If a healthy plant ecosystem is maintained, soil continues to grow. As healthy grasses have roots reaching down over 25ft, in some cases over 40ft, the potential for deep rich and highly productive topsoil is virtually limitless. With 40+% of the earth’s terrestrial surface supporting grasslands ecosystems, we could take virtually all the technologically accessible carbon in the earth’s crust (fossil fuels, carboniferous rock, etc.) and turn them into biologically cycled and accessible soil organics.
The grass life cycle.
The key to restoring ecosystem function is understanding the life cycle of grasses. Andre Voisin, a French biochemist, farmer and author, studied the effects of grazing on grass. In the process he devised a grazing system known as ‘Rational Grazing’, which capitalised on his ground-breaking scientific discovery, that overgrazing is not a function of animal numbers, but the time that a plant is exposed to grazing.
The results of his work were published in the book ‘Grass Productivity’, published in 1957. This work is considered one of the foundational works of the permaculture, holistic management and grass-fed beef movements.
What Andre Voisin discovered is that grass grows in a non-linear fashion. The growth curve of grass, plotted on a graph of plant produces what is called a ‘sigmoid’ curve, showing three distinct life stages.
Stage 1 is the stage described above, when the grass has been mown or grazed. The roots flush exudates into the soil to stimulate biology to deliver nutrients. Soon after this, the root system uses stored carbohydrate energy to initiate the growth of new leaves. This growth uses stored energy, and this is called ‘Stage 1’ growth.
Stage 2 is the stage when the leaves have become large enough to ramp up photosynthesis and begin producing new sugars and carbohydrates. At this point the growth accelerates rapidly and the plant produces most of its biomass. Toward the end of Stage 2, the plant replenishes its root system with carbohydrates and lignification begins.
Stage 3 begins with lignification. This signifies the plant has reached ‘full expression’ and it now begins a process of strengthening the plant vascular body. The plant then flowers, produces seed and enters senescence, which is the process where photosynthesis slows, the chlorophyll degrades, and the leaves begin to die.
Here’s the cool bit. If a grass plant is mown or grazed at the end of Stage 2 and the growing season is still favourable (heat, sunlight and moisture), the plant enters Stage 1 again and starts the whole process with no loss of sub-surface biomass. When this cycle is repeated, it becomes a biological carbon pump. Stage 2 sucks carbon out of the atmosphere and turns it into simple and complex carbohydrates. Grazing the plant puts it into Stage 1, where the plant pumps these carbons into the soil to restart the growth cycle. Each time the grass is grazed, a fresh batch of organic matter is pumped into the soil, building soil organics, supporting more biology and building the soil ecosystem.
Finally, it is worth taking note of the non-linear growth of the plant. For example, if the end of Stage 2 growth comes 30 days after grazing, 10 days after grazing only 10% of the plant biomass has been grown and 20 days after grazing the figure is only 41%. 59% of the growth occurs in the last third of the 30-day period.
If a plant is grazed early, the loss of short-term production is enormous. In addition, because the root system carbohydrate store has not yet been completed, an early grazing forces the plant to sluff off root mass because it no longer has the stored energy to keep it alive. Repeated early grazing slowly degrades the plant root structure and the overall system weakens, the soil degrades, and forage production drops off.
Andre Voisin’s discovery of the sigmoid growth curve and the resultant sensitivity of plants to the time plants were exposed to animal grazing, combined with the rest period required to reach full expression again, allowed subsequent researchers to make the connection between wild herd dynamics and ecosystem health. Most notably, Alan Savory, a Zimbabwean ecologist, credits Andre Voisin’s work as providing the breakthrough discovery required to rebuild grassland ecosystems.
On the 1st of May 2019, a research project by Quantis, an international scientific research organisation, on a ‘Savory Hub’ in Georgia (White Oak Pastures) determined that holistically managed beef production is carbon negative. For every kg of beef produced at White Oak, 3.5kg of atmospheric CO2 (or CO2 equivalent) is sequestered in the soil.
As mentioned one another page, ‘Is Livestock destroying the planet?’, there is a vast difference between conventionally raised livestock and properly managed livestock. Properly managing livestock requires the farmer/rancher to manage livestock to improve soil health. Improving soil health requires understanding the grassland ecosystem and the life cycle of grasses.
When this is achieved, however, the results are startling. Regenerative agriculture is growing rapidly in Canada and we have only just begun to discover the knock-on benefits of foods grown on healthy regenerating soils. Nutrient density and micronutrient profiles improve significantly and the benefits to human health appear to be dramatic.
It’s not ‘just grass’ or ‘just dirt’. Without them there’s no iPhone, truck, car, central heating, running water . . .