Soil fungi key to grass production

The soil is a complex world working hard to complete natural cycling

We always enjoy the cattle on 4-Clover Ranch near Rocky Mountain House, Alberta. It was our own animals back in the day and now someone else’s are on the farm for summer grazing. Fact is, we are really grass farmers and have chosen to harvest the grass with cattle rather than the haybine.

We have a really good relationship with the two cattle owners we work with who bring us cattle each year. On the grass-management side, we have reserved the right to decide which paddock the cattle graze in and for how long, and that hasn’t been an issue for the cattle owners. Quite the contrary perhaps as one of the herds is typically made up of first- and second-calvers enjoying some compensatory gain after a hard winter.

I have written before on the positive transformation of our pastures through planned grazing over 22 years and increased species diversity, nutrient cycling and carrying capacity. While I have been inspired by many good graziers over the years — some have become great friends — the grain farming part of my brain had a hard time accepting it was possible to harvest X-pounds of beef per acre without commercial inputs.

I needed some answers as to why we experienced the pasture improvements on 4-Clover Ranch as a natural succession only brought on by a change in management.

Learning about the process

It seems the main key in the transformation of what we were seeing above the ground is really a result of what took place below the surface. It has been said if there is an abundance of plant species above ground there is an equal diverse abundance of microorganisms in the soil below.

I recently watched a YouTube video of American mycologist Paul Stamets on mycelium, the vegetative part of the fungus. It helped immensely in understanding the processes. I found the video captivating as it so plainly highlighted the role of mycelium in building soil carbon, humus and holding the soil together. I also didn’t know fungi arrived 1,300 million years ago or 600 million years before plants, giving plenty of time to create the environment suitable for plant growth.

Mycelium or hyphae are really fungi “roots” and these microscopic hairs are extensive — one cubic inch of soil reaching up to eight miles in length — creating a network of pockets that can capture water and create a microclimate for other microorganisms, protozoa, amoeba, bacteria and enzymes. Mycelia produce oxalic acid, which is key in breaking down rock and freeing up nutrients that would otherwise be unavailable to plants. It took place over millions of years and became the process of the soil building and foundation for plant growth.

Hearing about Paul Stamets’s work gave me a much better understanding of why we had seen increased forage production without commercial fertilizer. We had noticed that the manure and urine spots in pastures were gradually disappearing and suspected it was due to improved nutrient cycling in the soil. Now I had an answer, the effects of soil mycorrhizal fungi and their symbiotic relationship with plant roots.

While I was excited I might have mycorrhizal fungi in our pastures I was looking for ways to know for sure. The answer came from the work of soil scientist Dr. Sarah Wright with the USDA. In 1996 she discovered a soil protein called Glomalin associated with mycorrhizal fungi. The sticky glomalin attaches to the hyphae and tiny roots of plants and holds water, sand, silt and clay and the dissolved minerals like phosphorous and calcium.

Slow process

It takes time for the mycorrhizal fungi to build. Tillage as well as leaving land idle destroys the fungi. Iron and aluminium often binds soil nutrients such as phosphorous and another USDA soil scientist Dr. Kristine Nichols found that the glomalin can bind these metals freeing up the P for the plants. As well glomalin slows down the carbon decomposition and stabilizes the organic matter.

Understanding the role of mycorrhizal fungi and glomalin and their ability to free up calcium and phosphorous and other macronutrients didn’t explain where the plants’ nitrogen requirement would come from.

A pasture full of legumes would have a fair bit of nitrogen coming from the rhizobia bacteria but soil biology researcher Dr. Elaine Ingham’s work at Oregon State University has broadened the scope. Understanding the role of soil protozoa, amoeba, soil bacteria and soil nematodes gives an explanation. Not only does the mycelium allow for housing these organisms but their lifecycle is very short. Simply speaking, the bacteria gets eaten by the protozoa, the protozoa get devoured by the nematode and the whole process releases massive amounts of ammonium.

Bacteria is microscopic, protozoa a smidgen larger and some of the larger nematodes can be seen with the naked eye. While we shouldn’t be confused with the larger undesirable nematodes that can cause crop damage, the good ones are too small to see with the naked eye. Just one teaspoon of soil can house 500 of the “good” nematodes. Their activity in the soil helps explain the mystery of why manure and urine spots were disappearing in our pastures.

Well-managed pastures ability to produce with lower inputs contribute to the bottom line, which is always good. Understanding these pastures’ ability to store enormous amounts of carbon and thereby contributing to a reduction in atmospheric CO2 emissions is an added benefit that society is awakening to and ranchers ought to celebrate.

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