"Mycorrhizal inoculants should be added to planting holes when installing woody ornamentals in landscapes" MYTH!!!!!! Read on:
Chalker-Scott, L. , Extension Specialist And Associate Professor, Washington State University
Downer, A.J., Farm Advisor, University of California
Beneficial fungi called mycorrhizae associate with roots of woody plants in a mutualistic relationship that benefits each partner. Decades of research have shown how plants inoculated with mycorrhizae grow faster and larger than those without these fungal partners (Carpio et al., 2005). This knowledge has prompted entrepreneurs to market mycorrhizal inoculant products as planting amendments, claiming they will ensure establishment of landscape plants. Mycorrhizal inoculants are often seen in container (potting) media, organic fertilizers, or sold separately as growth promoting products, but their efficacy is often unproven, especially in landscape situations (Chalker-Scott, 2017).
Misconceptions about mycorrhizal products are common:
- My soil is “poor” so I have to add the mycorrhizae to my garden. Most soils are already inoculated with mycorrhizal fungi, so they do not need to be added. Plants will form mycorrhizal associations in most soils without additional inoculant. Soils where mycorrhizal inoculants have been effective in promoting plant growth responses are extremely disturbed or toxic, such as mine spoils or severely “cut” sites where all surface soil is removed and plants are being grown in subsoils.
- Mycorrhizal inoculants will support my aging or dying tree. While research shows that mycorrhizae play a role in plant defense from pathogens (Linderman, 1988), there is no evidence to suggest that inoculants can provide additional benefit to previously inoculated plants.
- Mycorrhizae will promote growth of my established trees. There is no published work to indicate inoculation of established trees will promote their growth; Appleton et al. (2003) reported no effect from this application.
- The mycorrhizal inoculant contains viable spores. Biological products have limited shelf life. Research on commonly available inoculants showed that over 50% of the products available to consumers were not viable (Corkidi et al., 2003). Mycorrhizal fungi have naturally low viability of their spores so if a product does not have hyphal fragments included, it may not be viable.
- If I inoculate with mycorrhizae I don't need to fertilize my plants. Mycorrhizae aid in nutrient uptake (especially phosphorus), but they do not cure nutrient deficiencies, especially when the soil is deficient in those minerals. Research indicates that mycorrhizae can enhance uptake of normally available soil nutrients, but the soil has to contain them in the first place (Corkidi et al., 2005).
If I add mycorrhizae I will bring life to my soil. If a soil is devoid of microbial activity, it is likely an unsuitable soil for mycorrhizae to grow in. Just like plants, mycorrhizal fungi need good soil conditions in which to grow. Compacted, flooded, or contaminated soils are also harmful to these fungi, so they will not cure a toxic or otherwise non-arable soil.
- Author: Ben Faber
providing some advantage to the farmer. Frequently, these are new fertilizer mixes presented as proprietary cocktails promoted and dispensed with promises of a multitude of profitable (yet improbable) benefits to the buyer. With the large number of new products available, and the number of salespeople promoting them, it is often difficult for growers to distinguish between products likely to provide real benefit, and those that may actually reduce the profitability of the farm.
In all situations when a company approaches the University or a commodity research board with a new product or technology for sale to California growers, these institutions act as grower advocates. They are charged with sorting through the available information; asking the right questions; getting the necessary research done if the available information warrants this pursuit; disseminating accurate information on these new technologies and products, and doing all that can help maximize grower profits now and in the future. When approached with a new product or technology it is obligatory to challenge claims with the following questions:
Is there some basic established and accepted scientific foundation on which the product claims are made?
Language that invokes some proprietary ingredients or mysterious formulations, particularly in fertilizers mixes registered in the State of California, raises red flags. A wide range of completely unrelated product benefit claims (such as water savings, pesticide savings, increased earlier yield) raises more red flags. Product claims that fall well outside of any accepted scientific convention generally mean the product is truly a miracle, or these claims are borderline false to entirely fraudulent.
Has the product undergone thorough scientific testing in orchards?
Frequently, products are promoted based on testimonials of other growers. While testimonials may be given in good faith, they are most often not backed up by any real scientific testing where a good control was used to compare orchard returns with and without the product.
A “test” where a whole block was treated with a product and which has no reliable untreated control does not meet accepted standards for conducting agricultural experiments. Also, a treated orchard cannot reliably be compared to a neighboring untreated orchard; and a treated orchard cannot be compared to the same orchard that was untreated the previous crop year. Even a test with half a block of treated trees and half untreated is not considered dependable by any known scientific standard of testing.
Only a well designed, statistically replicated, multi-year trial allows for direct comparison of untreated versus treated trees with statistical confidence. Verifiable data from tests that meet acceptable standards of scientific design, along with access to raw baseline (before treatment) yield data from the same trees (preferably for the two years prior) should be used to determine the validity of test results provided.
Are the test results from a reliable source?
If the testing were not done by a neutral party, such as university scientists, agency, or a reputable contract research company using standard scientific protocols, this raises red flags. If the persons overseeing the tests have a financial interest in seeing positive results from the product, it raises red flags.
Does the product have beneficial effects on several unrelated farm practices?
A product that increases production of trees, makes fruit bigger, reduces pests, reduces water use, and reduces fertilizer costs, is more than a little suspicious. In reality, if such a product really existed, it would not need any testing at all because its benefits would be so obviously realized by the grower community that it would spread rapidly by word of mouth and embraced by the entire grower community.
Are other standard and proven farm products put down in the new product sales delivery?
If a new product vendor claims that their product is taken up 15 times faster than the one growers are currently using, or is 30 times more efficient, it probably costs 15 to 30 times more per unit of active ingredient than the standard market price. Growers should always examine the chemical product label to see what active ingredient they are buying. There has to be a very good reason to pay more for an ingredient where previously there had been no problem supplying the same ingredient at a cheaper price to trees in the past.
There are impartial sources of such information available to farmers to help corroborate information provided by product vendors. Perhaps the most reliable and accessible impartial research and education resources for growers are their local Cooperative Extension Farm Advisors and commodity research boards.
When promising products emerge, local university Farm Advisors can advise growers on how to evaluate these products and may help design a small trial to test a particular product on a few trees under local orchard conditions. If in these pursuits a truly promising new product or technology emerges, research board funding may follow but only on the recommendation of that board's Research Committee.
- Author: Robert Kourik
A little something that a friend wrote for gardeners, but is applicable to farming. You can read more of Kourik's stuff at:http://www.robertkourik.com/tidbits.html
Some garden suppliers now offer beneficial microbial and fungal inoculants to “boost” the soil's fertility. Some products tout the benefits of mycorrhizae inoculants for plant roots.
I contacted soil scientist Dr. Phillip J. Craul, a soil scientist and Senior Lecturer at the Graduate School of Design at Harvard University with the question: “what do the new packaged microbial and fungal products offer gardeners?” His immediate response: “I'm going to be frank, most of the time the home gardener doesn't need to fuss with (inoculants). Such products are only helpful in special cases where you're working with sterile material; (however), most of the biological analyses show enough organisms are usually present under artificial conditions to repopulate the soil—even in urban areas.”
In some cases, here with California native plants, inoculation with mycorrhizae had less new shoot growth—measured on a dry basis—than native soil.
“New Research in the Use of Mycorrhizaefor Nursery Production” by Lea Corkidi Mike Evans and Jeff Bohn, Tree of Life Nursery September 2008.
Furthermore, the soil's vast complex of biota defends its own territory from “invading” microorganisms. Existing microbes and mycorrhizae can be very good at fending off inoculants. According to Martin Alexander, “Microorganisms inoculated into non-sterile soil lead to poor growth and often the seeded species is eliminated in a period of days or weeks...(due to) a rivalry for limiting nutrients, the release by one species of products toxic to its neighbor and direct feeding of one organism upon a second.”
In a study with established willow oak (Quercus phellos), red maple (Acer rubrum) and pin oak (Quercus palustris) trees it was found that “Our data indicated no apparent measurable growth benefit [to estblished sreet trees], under the terms and conditions of this research, to inoculation with a commercial mycorrhizal fungal product unless combined with fertilizer.” “Mycorrhizal fungal Inoculation of Established Street Trees” by Bonnie Appleton, Joel Koci, Susan French, Miklos Lestyan, and Roger Harris. Journal of Arboriculture 29(2): March 2003.