MYCORRHIZAL PLANT TRIAL AND ANALYSIS

Mycorrhizal Basics

Mycorrhizal fungi are beneficial microscopic soil organisms that have evolved in a symbiotic relationship with approximately 95% of the world’s plant species over the past several hundred million years. Although these beneficial soil organisms have been a bit of a buzzword in the horticulture world over the past few years, mycorrhizae are not new; in fact, they have been around for hundreds of millions of years, quietly doing their important work beneath our feet.

The relationship between plants and mycorrhizal fungi is a two-way relationship of sharing resources between species: a classic symbiotic mutualism. The endomycorrhizal fungi rely on the plant to survive, and the plant’s performance and survival are enhanced by these beneficial fungi. Mycorrhizae act as a living extension of the plant’s roots and benefit a plant’s root system development, nutrient and water uptake and efficiency, stress tolerance, and transplant success. For a professional grower, mycorrhizal fungi can shorten crop times, improve plant uniformity, reduce nutrient runoff, allow for longer watering intervals, add to transport and retail resiliency, improve soil quality and health, and ultimately lead to happier plants and happier customers.

With a per-plant investment of as little as $0.0002 - $0.0008 when treated early in the plant’s life cycle, inoculating horticulture crops with mycorrhizal products provides an excellent and inexpensive insurance policy. Once the plant is inoculated and the root system is colonized by the mycorrhizal fungi, this symbiotic relationship lasts the lifetime of the plant as the mycorrhizal hyphae continue to grow along with the roots. With recent advancements in formulations and carrier technologies, it is now easier than ever for professional horticulturists to incorporate mycorrhizae into their growing protocols, and benefit from this fundamental symbiosis.

Even though it has been estimated that mycorrhizae have been around for over 450 million years, and many of us have been introduced to mycorrhizae through some educational or communication format over the years. Most growers these days know the main features of the mycorrhizal symbiosis, but most of us are still unfamiliar enough with mycorrhizae that we thought it would be beneficial to share with you a trial and analysis protocol for trialing mycorrhizae so you can better determine how the use of mycorrhizae can benefit you and your greenhouse or nursery operation. Plus, even when you’ve already done all of the research, there’s nothing like seeing the results with your own eyes in your own operation.

Trial Protocol

The first step in the trial protocol is plant selection. Often growers want to trial “problem” plants. This often is a poor choice. Since the plant is probably a “problem” plant due to several factors that may not all be positively impacted by the addition of mycorrhizae. We suggest you conduct your mycorrhizal trial with a plant that is key to the success of your business and a core part of your plant offering. Mycorrhizae can benefit specialty portions mycorrhizae use positively impacts your top sellers.

The second step is to determine which type of mycorrhizae positively impacts the plants you want to trial. About 8085 percent of all plants are Endomycorrhizal. This includes most greenhouse crops and commercially produced plants. About 5-10 percent of plants are Ectomycorrhizal. This includes most conifers and many hardwood trees. So, for most nurseries, you will either need an Endo/ Ecto product or trial both an Endo and Ecto mycorrhizal product separately. Five to ten percent of all plants either need a specialty mycorrhiza not commercially available (Ericaceae and Orchidaceae) or the plants are non-mycorrhizal (Brassicaceae and Caryophyllaceae). To be on the safe side, steer clear of the specialty or non-mycorrhizal plants, and if you utilize a product that contains both Endo and Ectomycorrhizae, the vast majority of commercially important crops will be able to benefit. Some companies offer Endo/ Ecto blends in powder formulations that are sold in 1 lb. packaging, making the initial investment in trial mycorrhizal materials very small.

The third step is determining the ideal application method for your crop and production protocols. With the array of mycorrhizal products on the market, there are now mycorrhizal inoculants that can be applied at almost any step in the process. These products can be incorporated/ mixed directly with growing media, added to water and drenched into porous media, used as root sprays/dips, applied via injector, boom spray, or irrigation, or even mixed with fertilizer directly in the stock tank and applied with a fertilization run. Whatever works best for you, make sure the product you select can be applied in a manner that is efficient for your operation, and be sure to follow the labelled application instructions to ensure the minimum rate of active ingredients are delivered to each plant, plug, or seed.

Fourth, you will set up your A-B trial. The simplest trial is to grow plants with and without the mycorrhizae treatment under similar growing conditions. Avoid adding additional variables, so you can clearly see the difference. Mycorrhizae should make your plant more effective and efficient in the uptake of nutrients and water. Wait to reduce fertilizer and water inputs until you have demonstrated the benefit of adding the mycorrhizae on its own. Under optimal growing conditions found in most commercial greenhouse and nursery operations, mycorrhizal benefits may not be obvious, hence the reason for this protocol. To avoid biological and environmental variables, use large numbers of plants (100 or more if possible) for each treatment. Be sure to label each treatment so you can track the performance of the treated plants. It is also a good idea to physically separate the two treatments. Mycorrhizae can transfer from one plant to another via a shared water source or physically if the application splashes during treatment.

Fifth, it is time to wait and see the results. Mycorrhizae begin to colonize newly emerging plant roots within a couple of days after inoculation but can be applied before the seed germinates or a cutting starts to root. The benefits of inoculation start to become more prominent to the grower approximately 8 weeks after inoculation. Typically, the plant starts to benefit after 3-4 weeks. For mycorrhizal evaluation trials, it is best to test trial crops with a total crop time longer than 8 weeks. We suggest applying mycorrhizae during propagation phase or after you receive plugs or liners, so you can start the process sooner and see positive results earlier. A grower of young plants (plugs & liners) needs to ensure homogeneity of the mycorrhizal application (soil incorporation or drench) due to the small soil volume in the plant cell. An additional benefit of applying the mycorrhizae earlier is reduced costs, since you are applying the mycorrhizae to a smaller soil volume. Once treated during propagation, the mycorrhizae stay with the plant throughout its entire life and moves with the plant when it gets bumped up into a larger container. The benefits of mycorrhizae will become more apparent when the plant is moved from the plug/propagation tray into the finished container. Typically, you only need to treat plants once with mycorrhizae during production of the plant.

Now, finally, it’s time to analyze the results of your trial! At the conclusion of your trial, analyze the plants and make comparisons between treatments that are important to you, your crop, and your bottom line. Visual comparisons are always good because those are important to both you and the buyer. If you have 100 plants of each treatment, then choose the best 20 plants and the worst 20 plants of each treatment and compare them side-by-side. Compare the top growth and compare the root systems of the treatments. Commonly observed differences include increased roots, shorter crop time, better branching, darker foliage, and more flowers. Typically, if the trial plants have gone under some sort of stress (heat, nutrient, or water) the comparison between the mycorrhizae-treated plant and the non-treated plants will be stronger, and the performance differences will be more pronounced.

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