The soil food web

The soil food web is similar to the food chain, except that the typical food chain is linear, while the soil food web works from the basis that everything that can eat or be eaten, is involved in a cyclical relationship. Soil is composed of two parts: minerals, which make up the nonliving portion of the soil, and the food web, which includes minute creatures, also called soil biota, which bring the soil to life. Soil biota come in many forms. Some help to build healthy soil and support healthy plants, and these are considered Beneficials. Others can cause many problems for gardeners, from root rots, to blights, molds, and mildews, and are considered pathogens. Both have a legitimate and important place in the growth and decay cycles of the natural world.

In the garden, we desire to increase the growth of the beneficial biota and suppress as many pathogens as we possibly can. When we improve soil tilth, texture, aeration, drainage, and nutritional content by feeding our garden compost and other amendments, we increase the amount of helpful soil biota. When these beneficial biota are active, the soil food web functions smoothly, and our plants flourish. Here's a brief explanation of the critters that create the soil food web and make the soil come alive.

Bacteria
Our native soils are full of bacteria, both beneficial and pathogenic. A handful of ordinary backyard soil may contain billions of bacteria of thousands of different kinds, many of them specific to a region. In general, they help water move through the soil more easily, they recycle organic matter, and they help ward off soil diseases. There are many types of bacteria, but one of the most important groups is the nitrogen-fixing bacteria. They eat particles of organic matter, creating a waste product called bacteria manure that adds new forms of organic material to soil. Most plants take up nutrients most efficiently through this bacterial waste product, so the more nitrogen-fixing bacteria in the soil, the healthier the soil. Bacteria and bacteria's waste products are also devoured by other soil dwellers of many kinds, so they feed other organisms in the soil in addition to feeding your plants. Lawns, flower beds, and most vegetables will flourish in soils dominated by beneficial bacteria.

Earthworms
Worms are among the most favorable of soil dwellers. Sadly, they are easily harmed or killed by exposure to many common pesticides and herbicides, including some commercial weed-and-feed lawn products. Most gardeners cherish their earthworms, knowing that these hard workers are the soil builder's best friends. Worms do the incorporating for us when we add a layer of amendments onto our garden's soil. They burrow through heavy soil to allow air to get down to plant roots. And their castings promote sturdy root growth and feed many soil dwellers. It would be hard to have too many worms, but soils suffer quickly when worms are in short supply.

Fungi
Most people assume that fungi must be bad for the soil, but this is really far from the truth. Fungi are vitally important to soil health, and beneficial forms are found in virtually every kind of soil on earth. Like bacteria, fungi break down organic matter by digesting and excreting humus, thus recycling nutrients through the soil food web. Mycorrhizae are among the best known fungi. They fasten themselves to the roots of plants and create a web of fine feeder roots that act like pumps, pulling nutrients and water into the host plant's root system. In effect, they increase the surface area of the roots and thus the plant's ability to absorb nutrients.Healthy woodland soils are dominated by fungi, with fungal creatures out populating the bacteria in the soil. To keep these woodland soils balanced, we need to sustain the fungal balance by allowing the leaves that fall, to be reincorporated into the soil. These leaves are often removed in the name of neatness, but this robs the soil of vital nutrients. To stop the leaves from smothering plants and to help the leaves compost more quickly, shred them and return them to the beds as mulch. Since trees and shrubs grow best in a soil dominated by fungi, clearing out woods by replacing the undercover shrubs with grass, usually results in unhealthy soil and stressed trees.

Arthropods
These recyclers are the critters that feed on bacteria, fungi, and earthworms, as well as plant particles. They include microarthropods- very small organisms like mites-and larger organisms like sow bugs, springtails, spiders, and centipedes. The microarthropods stay put in the soil, eating debris and generating nitrogen and other nutrients more eagerly available to plants and other soil biota. Arthropods also control the population levels of other organisms in the soil, keeping things balanced naturally.

Nematodes
Nematodes, like fungi, are generally assumed to be pathogens, but beneficial nematodes flourish in the soil. Quality garden soil contains an ample amount of beneficial nematodes, which feed on many types of creatures, from bacteria and protozoa to other nematodes, as well as the pathogenic ones. Nematodes support root growth, passing vital nutrients along to plants through their manure. Pathogenic nematodes eat live plant tissue, harming roots rather than promoting healthy root growth. In healthy soil, beneficial nematodes are vitally important in order to help keep their pathogenic cousins under control.

Protozoa
Soil-dwelling protozoa are single-celled organisms that eat bacteria, keeping the bad bacteria in check, and producing a manure rich in available nitrogen, which can be taken up by plants. Protozoa are a favored food for nematodes and other soil fauna, which, in turn, discharge nitrogen and other vital nutrients back into the soil as they produce waste.

In conclusion, soil has been, and always will be, the base for healthy plants. It doesn't matter how well plants were grown at the garden center, a quality plant will only decline, if grown in poor quality soil.