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8.01.2008

By WILLIAM PERSSON

On June 23, a class and field training session on using natural mycorrhizae was held at the Rutgers Cooperative Extension of Cumberland County, Extension Education Center in Millville, N.J. The class was titled, “Future Trends in Nursery Production: Using Natural Mycorrhizae, a Hands-on Experience.”
A study conducted with a Sustainable Agriculture Research & Education (SARE) grant, noted, “Nursery, greenhouse, and sod production ranked No. 1 among agricultural commodities in the last seven years in New Jersey. Nursery growers are under scrutiny due to excess use of fertilizers and excess nutrient losses to the environment. To develop methods that improve plant production while reducing nutrient loading into runoffs, we have developed a research study in May 2007 to assess the use of naturally occurring mycorrhizal fungi in increasing nutrient uptake, improving plant biomass, and reducing nutrient losses under three types of controlled-release fertilizers (Polyon, Osmocote, and Nutricote) when applied to oak, azalea and thuja seedlings.”
The study, and the class and field training, were supported as welll by Rutgers New Jersey Agricultural Experiment Station and the New Jersey Nursery and Landscape Association.
The study was coordinated by Gladis Zinati, assistant professor, Rutgers University, who was first to present. Zinati said that the aim of the study was “ to improve production with less use of fertilizer, less use of water, and less use of pesticides.” All three of those inputs cost money and the leachate costs money as well when it must be treated. And, of course, a higher water application means a greater amount of leachate – which might simply wash away valuable nutrients.
Zinati then discussed the learning objectives in the study and subsequent report. They were: “to provide growers with methods of identification (of the different mycorrhizae);” to show the method of “collection of naturally occurring mycorrhizal fungi;” and to teach “inoculation techniques for nursery crops.”
As a result “the growers will learn how to produce on-farm a wide range of naturally occurring mycorrhizae,” and, “about the storage conditions and cultural practices that may affect mycorrhizal colonization.”
Zinati explained that “Mycorrhizae ‘Fungus root’ is the symbiotic association between plant roots and beneficial fungi,” and, “Mycorrhizae facilitate nutrient and water uptake by the plant and receive carbon in return.”
Pointing out some other specific functions of mycorrhizae, Zinati showed mycorrhizae was helpful in “increasing plant resistance to drought in young seedlings; withstanding high temperatures for young seedlings; improving soil structure; and protecting the plant from root disease.”
Zinati identified three types of mycorrhizae and said they varied with the plant species — Ectomycorrhizae (oak, pine, birch, spruce, fir), Ericoid (rhododendron, azalea, mountain laurel), and Arbuscular Mycorrhizae (clethra, thuja, viburnum and ash gum)
Some of the results from the 2007 study are:
• Mycorrhizal-inoculated oak plants showed increase in biomass irrespective of fertilizer type;
• There was no significant increase in biomass in azalea and thuja plants in all fertilizer treatments whether inoculated or not;
• Nutricote seemed to be the best candidate for root colonization and protection of the environment from excess nitrate leachates.
The report concluded, “The integration of natural mycorrhizae in producing nursery crops in containers could increase plant growth, reduce nutrients in leachates and increase, in some instances, mycorrhizal root colonization. Thus, nursery growers could adopt such natural systems to be part of the nursery production and consequently such systems become the future trends in nursery and landscape management.”
John Dighton, professor in ecology at Rutgers University, then presented “The Use of Mycorrhizae in Woody Shrub and Tree Nursery Production.” While his presentation necessarily paralleled Zinati’s, Dighton more specifically discussed types of mycorrhizae.
He first emphasized what they were trying to do: “Optimize the use of fertilizer and water in nursery practice; use mycorrhizae to provide plant growth in reduced fertilizer and watering systems; identify best options for inoculum source; identify best time of inoculum addition; and provide guidance on production of inoculum.”
Dighton described the role of mycorrhizae in nutrient acquisition, water acquisition, defense against plant pathogens, sequestration of heavy metals and undetermined plant fitness improvement.
Dighton offered some pros and cons of using commercial inoculum. According to Dighton, the positives include: “A uniform material with similar composition of fungi represented in each batch.” Inoculum is “usually supplied in conjunction with bacteria, fertilizer and water-absorbing material;” and it is “easy to apply as a component of potting mix or post-planting drench.”
Among the negatives of using commercial inoculum are the cost and the fact that “particularly the Ectomycorrhizal inocula probably contain a limited number of fungi that can be cultured and usually represent only species colonizing young plants.”
Dighton’s alternative to commercial inocula is to “use natural inocula” which he said “contains a wide mix of fungal species;” and “may provide plants that are better equipped to be planted in a greater variety of soil conditions.”
Taking the class outside, Dighton dug up some soil and discussed where to get the natural inoculum, the idea of growing one’s own crop of inoculum, the methods of application and how they assessed plant response.
Returning to the classroom, students found six Olympus microscopes available to view the various mycorrhizae.
Asked whether the various mycorrhizae-treated plants had been introduced into existing landscaped areas and what effect this had on the existing plants, the researchers said they were doing that test now and that they are waiting for results of this test to be able to make the claim that they grow better in the field.