Did you know fertile and healthy soil is very much alive? In a thimbleful of fertile soil there may be 100,000 protozoa, two billion bacteria and 30 million fungal plants. In poor soil there may be few.
Under the forest floor, in fertile cropland, in your garden, is a silent (to us) beehive of activity of microscopic life — and death. It's the story of the eater and the eaten. This complex living community of organisms changes mineral and humus matter so its nutrients can be available to nourish plant and animal life of many kinds.
If you could closely look at some soil organisms, for example, you would see them attach themselves directly to plant roots. The result is symbiotic relationships beneficial to both. One example is the nitrogen-fixing rhizobium in legumes such as soybeans and alfalfa.
Other soil organisms act independently of plants and are free-fixers of nitrogen or other nutrients in the soil. While some organisms need humus and oxygen to survive, others are anaerobic — they don't need free oxygen. They gain energy by working on mineral matter.
When these organisms die, the minerals and proteins of their bodies are made available to plants or other organisms.
Now consider another vital factor in living soil — humus.
Decayed plant and animal wastes we call humus or organic matter. Humus feeds the majority of microorganisms in the soil.
Without the presence of humus and the activity of microorganisms we could not have renewal of topsoil from the subsoil below.
Humus and substances from microorganisms help cement soil particles in clusters or aggregates. This clustering creates pockets of air and gives good soil a crumbly, airy texture you can feel with your fingers. It discourages encrustation. The open air space in soils is critically important: It allows plant roots and microorganisms to breathe, instead of suffocate. Rains are absorbed deeper and faster into such soils rather than running off.
God made humus to play a vital role in soil quality and fertility. Humus-rich sandy soils hold more water and hold it nearer plant roots instead of letting water and nutrients leach out. Heavy clay soils need to be rich in humus, too, for them to be easily broken up and workable. Humus-bonded soils are more resistant to water and wind erosion. They better resist periods of droughts and floods. Heavy emphasis on use of chemicals and fertilizers in farming makes soil surface particles more erodible, and deeper soil particles denser, harder to work.
In fertile soil earthworms proliferate, as do other small soil creatures. Did you know that earthworms are like farmers in the soil with a hoe or plow? — only they charge nothing for their services! Earthworms pull in and mix humus in the soil. They bring up subsoil particles and mix sand, silt and clays in a loam of tons of rich castings on every acre. These workers of the soil are additionally invaluable as they help aerate the soil and make pathways for deep-seeking plant roots. A sign of sick soil in temperate zones is lack of worms.
Good farmers and gardeners respect the life of the soil. They protect their precious resource by returning sufficient humus, animal wastes or composts to the soil. This is the law of return essential for maintaining healthy soils.
Good farmers use appropriate conservation practices. They rotate crops. Crop rotation prevents rapid soil depletion. Crops used one year may be shallow rooted, drawing most of their nutrients from that level. The following year the good farmer plants deeper rooted plants, which draw much of their nutrients from another level. The soil is used more evenly and efficiently.
Under a good rotation system, different crops will use different amounts of essential nutrients for their growth, or they will add something to the soil helpful to another crop. Some legumes, like alfalfa for example, are nitrogen fixers and their roots reach deep into sub-soils for nutrients and thus place humus matter (their roots) in them. This helps condition sub-soils for later use as top-soils.
The law of return means that nutrients taken out of fertile soil must be given back in a constructive and useable form. Modern man's agricultural practices more and more are ignoring this cycle to the destruction of soils and humans supported by them. Modern man throws organic wastes away, he buries or burns them or washes them into rivers or oceans. He pours on powerful concentrations of chemicals. He pollutes his land and water supplies while the primary physical resource of his civilization — soil languishes and erodes away.
Whether we are only a small gardener or a big farmer, it is critical that we all learn to care for the soil as a living organism.