In a healthy soil there are literally hundreds and hundreds of species of soil bacteria, soil fungi, and many other microscopic soil organisms. The problem is that most of the soils that have been farmed conventionally have a very low population of these valuable and important soil microbes.
Many years ago a microbiologist reported that there are now some 2000 named species of bacterial and fungal microbes and estimated that there is an estimated another 10,000 species unnamed. More lately a figure of 20,000 species has been estimated. Of these approximately 14% are undesirable possibly causing problems in the soil and yet still have a role to play. The remaining balance of 86% microbes, given reasonable conditions, will keep the “bad” ones in check. Just how important are these microbes?
Let’s look at beneficial soil fungi in particular the very important Mycorrhizae.
Mycorrhizae (from the Greek “mukés”, meaning fungus, and “rhiza,” meaning roots) are a fungi associated with the roots of plants and have occurred naturally in the soil for 400 million years. Under the right conditions, they form a close symbiotic relationship with plant roots. This little known family of beneficial fungi live in and around the roots of 95% of the earth’s plant species that have not been disturbed by humans. When mycorrhizal fungi colonize the plant’s root system, they serve as a secondary root system by extending themselves far out into the soil. They extract mineral elements and water from soil for their host plant, creating a network that increases the plant’s capacity to absorb more water and nutrients such as phosphorus, copper and zinc. In return they live off the plant’s sugars, the root exudates. This process in turn enhances growth and favours rapid development of roots and plants. Plants with a good population of “mycorrhizal roots” systems are better able to survive and thrive in stressful man made environments.
Most Soils Lack Mycorrhizae
However, in most soils that have been disturbed by intensive cropping practices with applications of synthetic fertilisers, pesticides and other chemical products, the mycorrhizae content has considerably diminished, and has become insufficient to significantly enhance plant growth. These days however it is now possible to replenish your soil with these very valuable plant growth helpers. There are products now available, and these magical creatures, when in sufficient numbers, perform very important functions for your plants. The idea is to create the conditions for mycorrhizae at the root zone of a plant so they can attach themselves to the root system and start doing their good works.
While mycorrhizae, the beneficial root fungi, are very valuable, there are dozens of other beneficial soil fungi in a healthy soil performing many important tasks. Some fungi will, along with the bacteria, suppress common plant pathogens. Other fungi will produce various natural growth hormones that help plants grow healthier and have more resistance.
One is left to wonder why in most agricultural courses microbiology is not taught but rather the chemistry and the physical aspects of the soil are. It is so important to know about the role of these soil microbes.