The fungus that keeps on giving

A fungus is the key to regenerative agriculture as this story points out.

Beef and fungi go together long before they can be steak and mushrooms on a plate.

If truth be told, efficient beef production is utterly dependent on an organism known as arbuscular mycorrhizal fungi (AMF) because 90% or more of all forage plants can’t really survive, and certainly cannot thrive, without this curious symbiotic organism. Put simply, your grass needs fungus.

This relationship is well worth understanding because it can be managed and improved, thereby improving soil health, animal health, and the overall productivity of a rancher wise enough to make those improvements. (See “how to get more” story.)

“AMF are so important to the life of plants that a portion of most plants’ genome is dedicated to monitoring and controlling the symbiosis of AMF,” says Wendy Taheri, one of only a few authorities in the world on arbuscular mycorrhizal fungi.

The AMF can scavenge micronutrients from the soil which would otherwise be unavailable to the plants. It can help transfer water to the plants. It can produce protective compounds against pests. It has the ability to share nutrients among plants and across species. It also produces soil structure by way of byproducts called glomalin.

In turn, the plants produce sugars by way of photosynthesis; this is the carbon-based currency they trade to the AMF for their magic potions in this intimate marriage.

By this complex and fruitful relationship, the prairies and forests thrived for millennia without us humans pouring nitrogen, phosphorus and potassium on them.

Vital trading

The plant-AMF relationship is an extremely active one, usually with multiple species of AMF colonizing each individual plant. Taheri explains the plants can choose where to spend their carbon dollars and will trade more actively with arbuscules which are feeding them well, and cut back food from the arbuscules which are not. The arbuscules are the attachment points for the AMF, and are actually inside plant root systems.

In fact, Taheri says, “Arbuscules are ephemeral structures. They are formed, and when the hyphae they are attached to use up all the nutrients within reach, the arbuscule is dissolved. As new hyphae find new pockets of nutrients, new arbuscules are formed, and again dissolved when their usefulness ends. The symbiosis is dynamic!”

This relationship is beneficial to both organisms, a situation known as symbiosis, with the participants termed symbiots by scientists. The plants need the AMF, and the AMF cannot survive without the plants.

Extenders of everything

AMF are a fungi, as are the organisms which produce mushrooms, but AMF are non-fruiting. They are an organism which produces miles and miles of underground hyphae cells. It’s their version of roots, and they are so small you need a microscope to see them. AMF reproduce by way of spores released into the soil. Taheri likens spores with plant seeds. These are in fact the method by which Taheri and other AMF experts identify and count AMF species and content of soils.

One of the reasons AMF are so valuable is because they effectively add 10 to 100 times the surface area to the root system of plants, and possibly more. Taheri explains on average, AMF probably supply around 50% of a plant’s nutrients, and likely more in natural ecosystems like native grasslands, forest and savannahs. They can double water availability.

Additionally, the plants themselves directly trade sugars for nutrients with soil microbes which colonize their roots, but as we’ve noted, the AMF dramatically increase the total area which can make these and other trades. Soil microbes colonize the entire structure of roots and the AMF, and their entire life cycle adds nutrients to the life cycles of the plants and AMF. This compounds the special abilities of the AMF at gathering materials such as phosphorus, which are largely unavailable to plants and their comparatively meager root systems.

Starting early

They begin to attach to a plant in the seedling stage, with a colonization technique so intimate it’s at the cellular level. The fungi form a structure called an arbuscle inside the plant cells and then begin to trade signals with the plants as to desires and needs.

If you manage to improve AMF, everything else will come along with them, Taheri says.

Long-tilled farm ground can be completely void of AMF, says Taheri, but grazing managers are luckier because pastures will always have some AMF, and usually several species if they have not been heavily fertilized. The number of AMF and the extensiveness of their hyphae, on the other hand, is determined by management.

In the Texas A&M study of continuous grazing versus multi-paddock grazing directed by Richard Teague, the fungal proportion was considerably higher in the multi-paddock ranch than on either the lightly-stocked or heavily-stocked, continuously-grazed ranches. This went hand in hand with much higher levels of native, warm-season tallgrasses, which are highly dependent on AMF.

USDA

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