The world is an amazing place, and one of the entryways to amazement is through farming. The process of growing plants and raising animals alone can provide endless wonder. When you try to understand the surrounding ecosystem and work with it instead of against it, as those in sustainable agriculture do, even more surprises await every day.
I was struck with amazement recently by learning about the beneficial role of arbuscular mycorrhizal (AM) fungi in the soil. As I was inviting David Douds to present at the 2012 Southern SAWG Conference, I read about his studies on AM fungi at the Rodale Institute.
According to Douds, AM fungi are known as “obligate symbionts” because they must colonize plant roots to survive. In return for sugars from a host plant, the hyphae of the fungi – their long, thread-like structures – act as an extension of the plant’s root system and increase the plant’s access to nutrients such as phosphorus, zinc and copper. While plant root hairs extend 1-2 mm into the soil, the mycorrhiza’s hyphae can extend up to 15 cm from the plant’s roots. This relationship often enhances plant growth and yield.
But that’s not all...
In Rodale reports, mycorrhizae are also credited with increasing a plant’s disease resistance, improving a plant’s ability to grow under drought conditions, and improving soil structure. As AM fungi grow through the soil, they appear to selectively enhance populations of soil bacteria that inhibit the growth of plant pathogens. This reduces disease pressure on crops.
AM fungal hyphae also stabilize soil particles by physically “wrapping” the particles into small clumps or aggregates, and by releasing a glue-like substance that binds the soil particles together. Soil aggregates increase the number of empty spaces in the soil’s structure, which allows the soil to hold more air (for root and microbial activity), and improves the soil’s ability to absorb and retain water.
Now that is amazing!
AM fungi are found naturally in most soils around the world, yet many conventional agricultural practices harm them. Douds, along with researchers at the Rodale Institute, are developing practical ways for farmers to support the mycorrhizae that are already in place, and enhance them with low-cost methods of on-farm inoculum and production. You can hear David Douds present on this topic at the 2012 Southern SAWG Conference.