The Soil Ecosphere:
There are millions of microscopic organisms that live in the root zone of every plant. These organisms interact with each other and with plants as the "soil ecosphere".

How does the soil ecosphere affect plants?
Soil organisms create a living, dynamic system that must be understood and managed properly for optimal plant growth. Understanding soil health requires knowing what organisms occur, which ones are working, how many are present, and whether they are the right kinds for the desired plants. While some soil microorganisms are pathogens that cause disease in plants, many are actually beneficial to the plants they associate with. Plants depend on these beneficial soil organisms to protect them from pathogens, to help them obtain nutrients from the soil, and to break down toxic compounds that could inhibit growth.

How can the soil ecosphere be assessed?
Soil ecologists have developed methods to quickly assess the numbers, types and activity of each important group in the soil ecosphere. They are researching the effects of different methods of management and adding microorganisms, with the goal of improving soil health.

Soil ecosphere management is important
There's more to soil health than applying fertilizer containing nitrogen (N), phosphorus (P), and potassium (K). Plants thrive or suffer depending on the organisms around their roots. Beneficial soil organisms make nutrients available to plants, reduce nutrient losses, and help degrade toxic compounds. The traditional soil chemical analysis is incomplete without information about soil organisms.

The goal of soil health management is to understand what makes different types of soil healthy or unhealthy, and then to assess the current condition of your soil in order to develop a program of improving and monitoring your soil's health.

Balance among microorganism species is critical
For instance, most trees and shrubs do best in soil dominated by fungi. Most row crops and garden flowers do best in soil with an equal balance of Bacteria and fungi, while lawn grasses do best in soil dominated by bacteria. If the balance of soil organisms is wrong, fertilizers and pesticides can't help recover plant vigor. If you don't know what organisms are present in your soil, much of your management is being left to chance!

Plant husbandry is inherently a biological process. Since the value of forests, crops, and landscapes is immense, managing the root/soil organism environment will become a standard and powerful tool. The optimal number for each group of organisms in a healthy soil depends on soil parent material, organic matter (OM) levels, hydrology (distribution and circulation of water in the soil), climate, interactions between the organism groups, and the plant that is being grown. The species composition of each organism group is also affected by these six factors. Biomass of each organism group, however, has shown consistent levels. There is a good correlation between the biomass of each group of organisms with highest plant yields, or most rapid plant growth rates, for different crops in different soils, climates, hydrological conditions, and OM levels.

A balanced soil ecosphere will:

How do we know what a healthy soil is?

By testing for the following characteristics:

Elaine Ingham, Ph.D., Oregon State University and Soil Foodweb Inc. provided the concepts in this report. Information is from seminars held in Spokane, WA, on March 5, and in Moscow, ID, on March 6, 1999. Prepared by Don Dysart, WSU Cooperative Extension.

Agricultural Sustainability. Highlights from a seminar series conducted by Washington State University's Ag Horizons Team and funded by USDA Western Region SARE.