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New Study Boasts Benefits of Mycorrhizae

In a new study out of the University of California at Riverside researchers found that plants inoculated with mycorrhizal fungi were larger, contained more nitrogen(N) and phosphorus(P) and leached less N and P than plants not inoculated with the fungi.

The Use of Mycorrhizal Fungi to Increase Nutrient Use Efficiency and Reduce Nitrogen and Phosphorus Leaching in Nursery Conditions.

Lea Corkidi, Donald J. Merhaut, Edith B. Allen, James Downer, Jeff Bohn, and Mike Evens.

University of California, Riverside

Mitigation of nitrogen (N) and phosphorus (P) runoff has become a major goal of the nursery industry. Woody and herbaceous ornamental plant production is a significant source of surface water and ground-water nonpoint source pollution (Mangiafico et al., 2009).

Plant production is very intensive process; one acre of land can be occupied by numerous containers, and nursery cultural practices, such as the use of soilless mixes and frequent irrigation are highly conductive to nutrient leaching (Evens et al., 2007).

A number of Best Management Practices (BMPs) have been proposed to maximize production and minimize groundwater contamination from runoff and leaching losses. These practices vary with particular nursery conditions but most encompass proper irrigation and fertilizer programs to optimize nutrient use efficiency (Haver & Kabashima, 2005).

Inoculation with arbuscular mycorrhizal (AM) fungi can also be included as an important component of nurseries’ cultural programs to reduce nutrient runoff while maintaining plant quality and yield. AM fungi are a group of microorganisms specialized to colonize the roots of most plants, establishing a mutual beneficial relationship. They develop and extraradical mycelium that enhances the plant ability to acquire mineral nutrients and water (Liu et al., 2007).

AM fungi have been considered a valuable tool to decrease fertilizers because mycorrhizal plants of several species have reached similar growth with a fraction of the fertilizer rate required by nonmycorrhizal plants (Johnson & Menge, 1982). However, the direct effects of AM fungi on N and P leaching have seldom been quantified.

Mycorrhizal and nonmycorrhizal plants of Rhus integrifolia were grown in soilless mix without fertilizer or with half or full rate of 18N-6P-12K Osmocote® controlled release fertilizer.

Plants were harvested 8 weeks after transplanting and the shoot height, dry mass, Mycorrhizal colonization, and content of N and P in shoots were determined.

The concentration of nitrate (NO3), ammonium (NH4), and phosphate (PO4) was compared in leachates collected after irrigation from six-week-old plants of the different treatments.

Results: Plant Growth

Mycorrhizal plant grown in half and full rate of osmocote were taller and larger than nonmycorrhizal plants.

Fertilization with half and full rates of osmocote increased the growth of mycorrhizal plants but not the growth of nonmycorrhizal plants

Fig1. Shoot height and total dry mass of Mycorrhizal and nonmycorrhizal plants of Rhus integrifolia grown for eight weeks with no fertilizer; with half rate; and full rate of Osmocote® 18N-6P-12K controlled release fertilizer.

Results: Fertilizer utilization

Shoots from Mycorrhizal plants had a higher content of N and P than shoots of nonmycorrhizal plants

Fig2. N and P content in shoots of Mycorrhizal and nonmycorrhizal plants of Rhus integrifolia growth for eight weeks with no fertilizer or with half and full rate of Osmocote® 18N-6P-12K controlled release fertilizer.

Results: Nutrient leaching

Leachates from Mycorrhizal plants had a lower content of N and P than leachates from nonmycorrhizal plants.

Fig3. Concentration of nitrate (NO3), ammonium (NH4), and phosphate (PO4) in leachates collected after irrigation six week after transplanting. Mycorrhizal    and nonmycorrhizal   plants of Rhus integrifolia were grown with no fertilizer or with half and full rate of Osmocote® 18N-6P-12K controlled release fertilizer.

Results: Mycorrhizal colonization

The percentages of mycorrhizal colonization in the plants growth with no Osmocote or with half and full rate of Osmocote were not significantly different (53.8 + 5.7, 57.3 + 5.4, 45.0 + 3.3, respectively).

References
Evens, R.Y., Dodge., Newman, j., 2007 Nutrients management in nursery and floriculture. ANR, University of California, Publication 8221.
Haver, D., Kabashima, J. 2005 Nutrient management goals and management practices for nursery and floriculture. ANR, University of California, Publication 8221.
Johnson, C.R., and Menge, J.A. 1982. Mycorrhizae may save fertilizer dollars. American Nurseryman 155:79-86
Koltai, H., Meir, D., Resnick, N., Shlomo, E. 2008 Application of mycorrhiza to ornamental crops. Pp. 39-45. In: Feldmann, F., Kapulnik, Y., Baar, J. (Eds.). Mycorrhiza Works. DPG Selbstverlag.
Liu, A., Plenchette, C., Hamel, C. Soil and water providers: How arbuscular mycorrhizal mycelia support plant performance in a resource limited world. Pp.37-66. In: Hamel, C. Plenchette, C. (Eds.). Mycorrhiza in Crop Production. The Haworth Press, Inc.
Mangiafico, S.S., Newman, J., Merhaut, D. J., Gan, J., Faber B., and Laosheng, W. 2009. Nutrients and pesticides in storm water runoff and soil water in production nurseries and Citrus and avocado groves in California. Hort Technology 19 (2):360-367.