Cover Crops Bolster the Health of Mycorrhizal Networks – and Why That’s a Good Thing!

The mycelium of a fungus spreading through soil (Credit: Nigel Cattlin / Alamy)

The term mycorrhizae refers to fungi present in the soil and the positive influence it has on the root system of host plants nearby, aiding both to the health of soil biology and soil chemistry. These fungi enhance the uptake of water and nutrients, including carbon and nitrogen. They also contribute to suppression of weeds and pests.

The formation of these beneficial networks can be influenced by factors such as soil fertility, resource availability, types of host plants, tillage and climactic conditions. They form a symbiotic relationship with host plant; the fungi get nutrition from the host plant roots and the host plant gets a healthier soil in which to thrive.

Cover crops are conducive to the development and health of mycorrhizal networks. Once in place, mycorrhizae digest plant material, and produce by-products including polysaccharides. These complex sugars create a kind of aggregation in the soil, small clusters that farmers refer to as crumbs. A well-aggregated or “crumby” soil —not ”crummy” soil (depleted) – has more texture, better aeration, better infiltration, better water retention and is less prone to compaction.

Annual ryegrass is among the many cover crops that promote good aggregation. Grasses have a fibrous root system that spreads out from the base of the plant. These roots, in tandem with mycorrhizae, release the polysaccharides that then create the aggregation of soil between the roots. Aggregation is a sign that your soil is in the process of creating more organic matter, though a demonstrable increase (say, from 3 percent to 4 percent organic matter) will take more time. But a thriving mycorrhizal network is an indication that you’re moving in the right direction.

What is probably obvious to you at this point: tilling the soil discourages the development of mycorrhizae and the aggregation of soil, while also adding to the compaction of soil. No-till and cover crops are certainly important aspects of moving towards healthy soil, host to earthworms, microorganisms and mycorrhizae.

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