Most people aren't aware that 70-90% of the organisms in a rangeland ecosystem live underground, or that one cup of healthy soil contains more than 6 billion living organisms. The key to creating and maintaining a healthy soil is providing habitat and nourishment for the organisms that live there.
Just as microbes break down fiber in the cow's rumen, microorganisms in the soil break down fiber and other organic matter. As the microorganisms decompose organic matter, they create humus.
Humus stores nitrogen in the soil. With all our technology, that's something we have not figured out how to do. Humus holds 30 times more nutrients than clay. It absorbs five times its weight in water and increases oxygen availability in the soil. Microflora that live in humus attack soil pathogens. Humus is essential in a healthy soil.
Carbon Makes Things Go The primary food required by plants is the same as the primary food required by cows, sheep and people. It is carbon. Carbon is energy. It makes things go.
While organic matter in the soil has a high proportion of carbon, plants get nearly all of the carbon they use from the atmosphere. Through the miracle of photosynthesis, plants take energy from sunshine, carbon from the carbon dioxide (CO subscript 2) in the air and water from the soil.
From these, they produce starch, cellulose, sugars, proteins and other carbon-based compounds. These substances are consumed by animals and decomposed by soil organisms, releasing CO subscript 2 into the soil. In nature, unless consumed by fire, nearly all carbon is recycled into the soil.
Maintenance of organic matter is important for many reasons, not the least of which is providing adequate carbon to feed the soil microorganisms. It's critical that sufficient crop and root residues be provided to replenish the organic matter.
While nature returns nearly all-organic matter to the soil, modern agriculture removes most of the organic matter. Farming and ranching will not be ecologically (or economically) sustainable until we replenish and maintain soil organic matter.
According to Australian soil scientist Christine Jones, "pulsed" grazing (short graze periods with adequate recovery periods) adds organic matter to the soil and is the most effective grazing method for maintaining healthy soils.
Nitrogen Makes Things Grow If carbon makes things go, nitrogen makes them grow. Our atmosphere is 78% nitrogen. But unlike carbon, nitrogen in its gaseous form is not useful to plants. In order to pass from the atmosphere to plants, nitrogen must first be "fixed" by the soil microorganisms.
Almost all of the nitrogen in the soil is in the organic matter. But, plants are not able to use the complex protein molecules in these materials. Only after the microorganisms have broken down these complex molecules into ammonium and nitrate molecules will the plants have a nitrogen source.
Just like the microbes in the rumen of a cow or sheep, the soil microbes need protein (nitrogen) in order to use the energy (carbon) in the soil's organic matter. And, just like the rumen microbes, the soil microbes need carbon and nitrogen in the correct proportion.
Too much carbon (relative to available nitrogen) and the microbes can't convert the organic matter to humus. The microbes will tie up all the available nitrogen, making it unavailable to plants. Too much nitrogen (relative to available carbon) and the microbes, in search of carbon, will devour the humus leaving the soil impoverished. A carbon:nitrogen ratio of 25-30:1 is ideal for the microbes.
Returning adequate organic matter to the soil and encouraging its decomposition into humus are essential for healthy productive soils. But, most farming practices deplete organic matter and destroy humus.
Replenishing soil organic matter and maintaining a thriving soil microbe population are essential in any business that is ranching for profit.