Mycorrhizal Fungi increase uptake of nutrients by increasing the surface absorbing area of roots 100 to a 1,000 times! This is like having way more than a second set of roots! They work in both natural soil and with fertilizers added, especially phosphorus. P is for flowering, so increases production. The fungi also release powerful enzymes into the soil that dissolve hard-to-capture nutrients, such as organic nitrogen, phosphorus, iron and other “tightly bound” soil nutrients. The extra nutrients can fuel better growth and increase resistance to drought and disease. Plants in soil with well-established mycorrhizal fungal root systems are better able to survive droughts and transplant shock, and the fungi’s ability to alleviate salt stress is well documented.
Two exceptions to using MF: 1) When the soil already has such ideal nutrient and moisture levels that the plants can scavenge enough on their own. 2) with Brassicas (members of the mustard family), because they do not allow the mycorrhizal fungi to colonize their roots! Save your time and money!
There is so much more known now due to research the last 40 years! David D. Douds, Ph.D., a microbiologist with the USDA Agricultural Research Service (ARS), notes that different species of plants have different tendencies toward developing mycorrhizal associations. For example, he has found that leeks greatly benefit from mycorrhizal association in most years, while tomatoes and peppers are more likely to benefit when they are more nutrient-or water-stressed. Brassicas such as turnips and radishes do not form mycorrhizal associations under any conditions.
Recent research shows mycorrhizal plants warn each other when disease or pest infestations occur. ‘The uninfected ‘receiver’ plants also activated six defense-related genes!’ The infected or infested plant may die, but the others live!
Don’t kill your Mycorrhizal Fungi!
Day to day gardening can degrade and destroy delicate mycorrhizal fungi, and the mycorrhizae-forming potential of your soil. Not good. Tilling and hoeing, removal of topsoil, erosion, site preparation, compaction (removes air and damages filaments), fumigation, relentlessly removing weeds, and leaving soils fallow without a deep mulch covering, are some of the activities that can reduce or eliminate these beneficial soil fungi. Scientific studies indicate endo mycorrhizal fungal populations are slow to recolonize, unless there is close access to natural areas that can act as a source of mycorrhizal spores to repopulate the affected area. Reintroducing mycorrhizal fungi in areas where they have been lost can dramatically improve plant performance with less water and fertilizer and at a reduced cost.
So, for example, if you just dug up an area to install gopher barriers, that area needs some babying, tender repopulating. And you can see this is a huge reason to do lasagna gardening, or sheet composting. Put the nutrients, compost on TOP of your soil. Don’t dig up your soil and destroy the mycorrhizal network and soil structure of the micro herds of soil organisms, or the mini air tunnels earthworms make that let your soil breathe and moisture to soak in! Don’t be shy! Pile it all on a foot to 18″ deep! Remember, that pile will rapidly settle to about 6 to 8″ deep. For immediate planting, pull some holes open, add a tasty compost, and plant away!
Tips to Help your Mycorrhizal Fungi Flourish!
- Add fungi! Sprinkle dry or pour or spray liquid fungi right on the roots as you put in your transplants, except those Brassicas. Use a core drill or auger and put liquid fungi down into your soil. Not only does it help veggies, but your turf grass as well! While you are at it, put in some compost tea in alternate holes to build your soil herds. You will be amazed at the results from these amendments!
- If your soil is already high in phosphorus (get a soil test), do not fertilize with a phosphorus-rich amendment, because too high phosphorus levels inhibit development of associations between plants and mycorrhizal fungi. Manures and manure-based composts can be high in phosphorus, so test these amendments before adding them.
- Minimize digging (especially rototilling), as it can break mycorrhizal hyphae, preventing them from colonizing new plant roots and transporting nutrients.
- Don’t let your soil dry out! Cover it deeply with partially composted leaves and other organic material if you aren’t planting there right away. Plant densely enough that your plants are living mulch. Or, simply water anyway until you are ready to plant. If it will be an extended time, best of all is to plant a quick growing soil-feeding cover crop!
- Grow a diverse mix of plants in your soil for as much of the year as possible, because mycorrhizae need active plant roots in order to develop.
- If you decide to use mycorrhizal inoculants, look for a company that produces the inoculant in your geographic region.
Elaine Levine suggests techniques to keep your mix diverse:
• Rotate crops each year (as long as there aren’t too many successive brassicas). Crop rotations are vital to mycorrhizal fungus populations because, in addition to providing a continuous succession of root hosts, different crops also tend to favor different species of mycorrhizal fungi.
• Plant a cover crop. In addition to adding organic matter and retaining soil nutrients, the cover crop offers host roots for the mycorrhizal fungi to colonize and helps them proliferate in preparation for your next planting. A good mix of crops above ground is the best way to support a mix of beneficial fungi below ground.
• Lighten up a bit on weed control, because, surprising as this may be, weed roots can also be excellent mycorrhizal hosts.
Santa Clara Master Gardener Elaine Levine says ‘These simple, no-cost steps help keep the soil’s native population of mycorrhizal fungi healthy and diverse, harnessing yet another gift of the natural environment to create a vibrant and abundant garden.’ She’s so right!
TheEarthProject.org says: Arbuscular mycorrhizal fungi [AMF] is the medium of soil structure, it determines the flow of water, nutrients, and air, directs the pathways of root growth, and opens channels for the movement of soil animals. As the moderator of the microbial community, it determines the metabolic processes of the soil. In other words, the mycorrhizal network is practically synonymous with ecosystem function.