Life Beneath the Soil

Life beneath the soil

For the market farmer, soil health is critically important. The soil is a generic term for the upper layer of the Earth’s crust. In fact, there are six soil layers that impact market farming and even big Ag via the life within the soil, the overall soil health, and the relationship therein. Inside we discuss the life beneath the soil and how those organisms affect soil health.

Soil Biota

Biota is the life – animal or plant – that exist in a specific habitat or environment. All the fish, plants, algae and other organisms in the Pacific Ocean would be the biota of the Pacific Ocean. Soil Biota is the organisms that live in the soil of a specific area or environment, such as your garden or market farm. For most plots of land, we are talking about organisms such as bacteria, Fungi, spiders, worms, arthropods – insects, spiders, crustaceans, etc., small rodents and mammals, etc. In short, there is a lot of life in the soil – Some of it good and some a little challenging for farmers and gardeners – all of it seems to be essential for growing food.

The Layers of the Soil from top to bottom

  1. Humus — In healthy soil, there is a thick layer of humus which is the off-cast parts of plants — leaves, bark, stems, fallen fruit, etc. It is in the humus where new soil is created and nutrients within top soil replenished. That process is in thanks to the soil biota and the hydrologic cycle — rain and water.
  2. Topsoil — a nutrient-rich layer — usually — where most plant roots are found. Larger trees and shrubs may have roots that extend as deep as the subsoil layer.
  3. The Eluviation layer — Often a sink for soil nutrients as they are carried down through the humus and topsoil layers by water. This is generally a small grained layer of soil particles.
  4. Subsoil — The subsoil layer is made up of tiny grains of rock, soil, and clay. There is not much organic residue in the subsoil layer, but it can be an excellent place for the natural storage of excess water – especially in areas with a lot of clay. This can also be a place where hardpan forms.
  5. Regolith — Upper Bedrock – a broken layer of bedrock – this is where bedrock begins to decompose thanks to physical and chemical weathering.
  6. Bedrock — The bottom layer of the soil is bedrock on which the upper layers of soil rest. Bedrock is exposed due to erosion. We see that naturally on the upper reaches of the mountains. We also see it farming in extreme cases where air or water erosion is uncontrolled.

Little Creatures with a Big Impact

Bacteria and fungi are microscopic, but both do a fantastic job converting organic compounds into nutrients. Nitrogen-fixing bacteria are literally the driving force behind life on earth through a process called the nitrogen cycle. The air we breathe is nearly 78% nitrogen, yet plants cannot use nitrogen in its gaseous form. There are a few ways that nitrogen becomes usable to plants and nitrogen-fixing bacteria are one of the most efficient means.

However, it is not just nitrogen that makes soil healthy. It is also aeration thanks in part to critters like earthworms, moles, voles, shrews, and even insect larva that help to “fluff” up the topsoil and humus layers so that air is available for all organisms to use. It is also about the ratio of organic matter in the soil to the amount of moisture that the ground holds. The humus layer helps the topsoil layer to retain water and by decreasing the amount of evaporation that occurs. In the humus layer are all kinds of organisms that help to reduce plant matter so that the bacteria and fungi can do their jobs. That is a natural, organic cycle. The plants grow, shed their fruit and leaves, which become the humus layer where the organism’s consume the debris and turn it into usable nutrients.

Supplements for Soil Health

In commercial farming, the humus layer is burned off or removed. Over time, the topsoil layer becomes compacted due to the reduction of organic material and the farmer must then supplement their lands with inputs — nitrogen-based fertilizers — because there is not enough life in the soil to regenerate the nutrients. Market farming does not have to follow this path. Many small farms are using other methods such as no-till to improve the condition of their soil. There are other tricks too, such as cover crops that utilize nitrogen-fixing plants. Nitrogen fixing plants are a symbiotic relationship between specialized bacteria and the plant. Together they help to absorb nitrogen or nitrogen components and then convert it into a usable material that the plant can use to grow.

Soil health is a relationship between many small organisms, the plants that grow in the soil and the amount of water available. The small farm can take advantage of these relationships to produce more food or flowers and use fewer resources.

David Stillwell organic gardener

About: David Stillwell is an organic gardener, entomologist, writer and student. David specializes in hymenoptera – bees, wasps, and ants, and the study of cecidology – Plant galls. He has a fondness for recognizing natural circles and energy webs that exist in nature — those interconnected natural systems such as food webs. He is a native of California and an advocate for conservation, locally grown, and farmer’s markets.