Pittsburgh Garden Experiment

There's a lot of hype right now about soil biology. Here's a (very) brief summary of what I know.

Basically, healthy soil is made up of thousands of species of microbes. They can be broken down into bacteria, fungus, protozoa, and nematodes. Each has a specific role in the breakdown of organic matter and the overall health of the soil. Together they make up what's called the "soil food web."

Nutrients aren't available to the plant until they are broken down by bacteria and protozoans. Soil is also held together and protected by many species of fungus. The ratio of bacteria to fungus determines what type of plant can thrive there. Early in soil life, bacteria are hard at work breaking down organic matter and sequestering nutrients. As soil naturally develops into forests over hundreds of years, fungus creates structure in the soil and sequesters different nutrients. Plants such as vegetables require a bacteria to fungus ratio of roughly 1:1.

Think of chemicals as a communication tool between microbe species. A plant growing in the soil will send out sugars which attract a certain type of bacteria. Bacteria will cluster around the roots and be eaten by protozoa. The protozoa release the nutrients into the soil for absorption by the plant root. In this way, the plant asks for the correct nourishment, and the soil system is healthy enough to deliver.

Maintaining healthy soil is a delicate balance. The greater the active life in the soil, the easier it is to disrupt the balance. Certain populations of healthy nematodes and protozoa can be killed by a heavy rain. Healthy biological soil, however, has shown resiliency against disease, pests, drought, and flood in tests around the world.

Out of the hundreds-of-thousands of microbe species, only small percentage can be identified or grown in a lab. The best way to ensure that your soil is maintaining the correct levels is to use quality compost from a variety of quality sources. Compost can be applied to the soil or as a foliar spray. As microbe levels stabilize in the soil, less compost will be needed to maintain soil balance. Non-native species may die off after a few years though. The only way to tell right now is to have your soil biologically tested.

A conventional chemical analysis of nutrient content will only tell you what's currently available. It does not take into account the living aspect of the soil. The best way to check the biology of your compost or soil is to get it tested under a microscope by a trained eye.

 

Please comment or suggest good websites.

 

• soil
• biology
• microbes