RIVERSIDE, CALIFORNIA--Nursery container plant production is an intensive practice. In some large-scale operations it's common for 1 acre of land to support thousands of container plants. Cultural practices in nurseries, such as the use of soilless mixes, high fertilizer rates, and frequent irrigation, can result in increased leaching of beneficial plant nutrients. To maximize production and minimize water contamination from runoff and leaching, best practices such as proper irrigation and fertilizer regimes are incorporated to optimize nutrient use efficiency.
Another emerging method called mycorrhizal technology can also play an integral part in nurseries' attempts to reduce nutrient runoff while maintaining plant quality and yield. The technology uses mycorrhizal fungi, microorganisms that colonize around the roots of plants, establishing a mutually beneficial relationship. The fungi settle in the area around roots, forming thin filaments that enhance the plant's ability to acquire beneficial nutrients and water. Growers know that plants, trees, and shrubs with well-established mycorrhizal fungal root systems are better able to survive droughts and transplant shock. Mycorrhizal fungi have also been shown to boost plants' immune system, making them more resistant to soil-borne pathogens.
Research published in HortScience investigated the effects of mycorrhizal colonization on nitrogen (N) and phosphorus (P) leaching from plants grown in nursery containers. Using native California plants--the fast growing perennial California sunflower (Encelia californica), and a slow growing woody shrub called lemonade berry (Rhus integrifolia)--researchers compared the growth response and the content of nitrate, ammonium, and orthophosphate in leachates collected from mycorrhizal and nonmycorrhizal plants. According to author Lea Corkidi, the plants used in the experiment were chosen because "they are both important components of the coastal sage scrub and chaparral communities and are widely propagated to be used as ornamentals and for ecological restoration." The plants were grown for 8 weeks with no fertilizer or with half-rate and full-rate controlled-release fertilizer.
According to Corkidi, the study was designed to determine whether mycorrhizal colonization significantly decreases nitrogen and phosphorous leaching, then to determine whether any leaching is related to plant growth, to the extent of mycorrhizal colonization, and/or to the concentration of fertilizer in the growing medium. The experiment showed that mycorrhizal colonization increased the growth and nutrient uptake of both California sunflower and lemonade berry, but was more effective at decreasing nutrient leaching from plants of Encelia californica. "Although the effects of mycorrhizal colonization were not always reflected in decreased content of N and P in leachates from Rhus integrifolia at all fertility rates, the potential still exists to use mycorrhizal inoculation to reduce N and P leaching for the propagation of both species without affecting their plant growth," the researchers said. "This study shows that mycorrhizal colonization can reduce N and P leaching either by increasing nutrient uptake or by allowing the use of lower fertilizer rates."
The complete study and abstract are available on the ASHS HortScience electronic journal web site: http://hortsci.ashspublications.org/content/46/11/1472.abstract
Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at ashs.org
Effects of Mycorrhizal Colonization on Nitrogen and Phosphorus Leaching from Nursery Containers
Lea Corkidi, Donald J. Merhaut, Edith B. Allen, James Downer, Jeff Bohn, and Mike Evans
HortScience 46:1472–1479. [Abstract][Full Text][PDF]