The Basics of Understanding Mycorrhizae

GolfLandscape

As the Fall aerification season creeps towards us, mycorrhizae again becomes a hot topic of conversation and discussion in the turf world. Even though it is one of the most utilized biostimulants, not everyone understands what they are and, more importantly, what benefit they can deliver. The symbiotic relationship between the turf plant and their mycorrhizae is fairly complex, so let’s breakdown a cursory review of “all things” mycorrhizae.

What are mycorrhizae?

Simply put, mycorrhizae are a fungus that exist as very tiny threads called hyphae. The hyphae are all interconnected into a net-like web called a mycelium, which measures hundreds of miles in length that are all packed into a small area around the plant’s roots. This mycelium extends outwards and connect multiple plants and other mycorrhizae to form colossal spider-web looking mash-up called a common mycorrhizal network. In a common mycorrhizal network, it is impossible to tell where one mycorrhiza ends, and another begins due to massive colonization of the mycorrhizae on the turf’s roots. Because of this vast network, a single turf plant can be connected to a completely different species of turf plant halfway across a golf course or your front yard.

How do mycorrhizae connect to turf plants?

The short answer is…in two ways. You’ve likely heard the two terms, endomycorrhizae and ectomycorrrhizae, which are two different strains of the fungi that connect in very different ways. The ectomycorrhizae simply surrounds the outside of the roots. Of the two strains, this is the least beneficial to turf, primarily due to not attaching itself to the turf plant and the fact they only form relationships with 5% of all plants. Endomycorrhizae, on the other hand, actually grows inside the turf plant by squeezing their hyphae between the cell walls and membranes of the roots. This intimate relationship with the turf plant serves as the underlying reason for being so efficient. It actually gets a lot more complex than this, with many sub types of each main type existing, but this is enough to go on with for now.

Interestingly, all the perennial grasses, including Kentucky bluegrass, creeping bentgrass, and fine fescues naturally associate with mycorrhizae in symbiotic partnerships. Oddly enough, the annual grasses, such as Poa annua do not.

How do mycorrhizae benefit turf plants?

Turf plants can get nutrients themselves through their roots, but they have a limited ability to do so. The roots need to be in direct contact with the soil to absorb the nutrients and turf roots only are only so small.  Fungi, on the other hand, are much smaller. Fungal hyphae can wedge in between individual bits of soil to cover almost every available cubic millimeter of soil. This increases surface area and allows the plants much greater access to nutrients than they could get by themselves. This equates to greater and more efficient uptake of nutrients and water by your turfgrass. The mycorrhizae absorb nutrients such as potassium and manganese and bring it directly to the plant roots.  

From this we can deduce that turf and their symbiotic fungi partners evolved to work together for mutual benefit. And it is not hard to see why these useful fungi would want to form lifelong partnerships with turf plants either. Remember that turf plants are efficient sugar producing factories, using photosynthesis to make high energy food out of thin air and sunlight. The mycorrhizae partners of turf plants benefit from this talent in return for helping the plants to extract more nutrient and water from the soil than they could on their own, which of course allows each grass plant to grow and become an even more efficient food factory and attractive partner for the mycorrhizae. It is a fair trade, and both sides benefit.

It can be difficult for us to think of high-quality turf and fungi as one thing, but it’s quite unlikely that we would have such fine, manicured turf in its current form if this process wasn’t happening underground.

Aren’t there already mycorrhizae in the soil?

Yes and no. Natural areas, like forests and other non-disturbed settings are indeed full of beneficial soil organisms, including mycorrhizae fungi. These areas have well established networks being utilizes beneath the soil.  However, golf courses and home lawns are far from natural settings. Research shows that disruption of soil through common site-preparation practices such grading, tilling, compaction, and removal of natural vegetation significantly reduces mycorrhizae populations. Also, standard turfgrass cultural practices like dethatching and verticutting also contribute to lower than desired fungi numbers. To have healthy soil and thriving turf, it’s important to reestablish these beneficial fungi whenever possible; new seeding, laying new sod or when you’re aerifying.

What are the real-world benefits to my turf?

This is the always the $64,000 question when it comes to using mycorrhizae fungi as a part of a turf management program. Here is a quick list of the benefits what you can expect once your turf’s soil is teeming with mycorrhizae fungi:

  • Maximized use of fertilizers. The extensive tentacle-like filaments that mycorrhizae send into the soil release enzymes that unlock all the available macro and micronutrients. Studies have shown that soils with established mycorrhizal networks require up to 50% less fertilizer.
  • Healthy root systems. Thick, robust turf stands growing in “living” soil help manage environmental stress and keeps the plant actively growing.
  • Aerification recovery. Due to the active nature of the mycorrhizae network, the holes created during aerification fill in significantly quicker than in soils without the beneficial fungi.
  • Increase in turfgrass establishment. Inoculating your site with mycorrhizae when preparing your soil for seeding increases rate of establishment and significantly increasing the root biomass. This can mean obtaining the grass coverage you desire with the first seeding, rather than having to reapply several times.
  • Binds soil. Mycorrhizae bind soil particles, which improves the porosity and drainage of soil, which allows for better air and water movement throughout the soil. The lack of compaction leads to healthier turf root growth.
  • Improved drought resistance. Mycorrhizae’s ability to reach deep into the soil for water and make it available to your turf that is better able to withstand drought. Studies have shown that soils with established mycorrhizal networks require 30% less water during the summer.
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