Natural, Man-made Mix Promises Biggest Landscape Plant Growth

And that's just the plant aisle.

Fertilizers for gardening are a major growth industry, so to speak, with U.S. consumers and nursery owners spending millions every year for mixtures aimed at improving the health of their greenery.

But a recent study points to an inexpensive natural additive that makes better use of some fertilizers, saving not only money but improving the environment, according to Texas Agricultural Experiment Station researchers.

"When a plant suffers from stress, it suffers just like when we are stressed," said Dr. Fred Davies, Experiment Station horticulturist. "This study showed a way to get better plant growth while allowing for a more judicial use of pesticides and water."

Davies, Experiment Station horticulturist Dr. Michael Arnold and then graduate student Lucila Amaya Carpio studied mycorrhiza (my-co-RIZE-ay), a microscopic fungus in the soil, incorporated with either synthetic or natural fertilizers and applied to bush morning glory. Their finding that mycorrhiza mixed with synthetic fertilizers yielded better plant growth and nutrition contradicts previous notions that the fungi work better with just organic, slow-release fertilizers, Davies said.

A report on their research will appear in the Journal of the American Society for Horticultural Sciences later this year. Mycorrhizal fungi evolved with plants over thousands of years and formed a beneficial relationship. Now available under several product names, these fungi are used to ease plants through stressful times in their lives.

"In other words, they make it easier for the roots of plants to access water and nutrients, which is important in producing plants and establishing them in the landscape/garden," Davies explained.

Though somewhat beneficial under a variety of conditions, this plant "upper" seems to work best when blended in with a synthetic, controlled-release fertilizer, the study found.

"That's good information for both home gardeners and commercial nurseries," Davies noted.

Good information, he explained, because the more fertilizer added to a landscape or greenhouse plants, the more money it costs. Commercial growers and home gardeners largely use synthetic fertilizers — those made from chemicals — as compared to organic fertilizers such as fish meal and manure.

"That's the practical side. Not having to apply as much fertilizer and being more successful in growing plants in the landscape makes a happy consumer," he said, "and a happy consumer is a repeat customer."

Carpio, who conducted the research for her doctoral degree, agreed on the value of doing studies that are beneficial for the public and industry.

"We were expecting an improvement but somehow thought the organic fertilizer would be better, and we didn't expect such a big difference," said Carpio, a Venezuelan native now is in charge of research for a potato company in Dalhart.. "I love to do work that has meaning, that industry can use and (can) give us a better understanding of how to grow crops better."

The journal article reports on the team's work on bush morning glory, a plant that Texas horticulturists are developing for ornamental use. They hope to breed a bush morning glory that has less seed production to reduce weediness and with improved flowering and more compact growth, according to Arnold.

"These are a bit away from release (to the public for landscapes), but there are some trials with this species at the Texas A&M gardens this summer," he said.

Carpio said for her graduate research, mycorrhizal fungi were tried on five other landscape plant species in addition to the bush morning glory.

"The amazing thing was that the mycorrhizae with the inorganic fertilizer was the most useful and better than the organic fertilizer mix. Most all of the (scientific) literature talks only about using mycorrhizae with inorganics," she said. "I'm devoted to this microorganism. It's something I would like to test with potatoes now."

Davies pointed out that mycorrhizal fungi are not a panacea, and not all plants benefit from additions of the fungi to the soil. But he hopes this research is a start toward helping growers and gardeners use the best management practices for the environment and for the least cost.

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More information about mycorrhizal fungi and the research can be found at http://aggie-horticulture.tamu.edu/faculty/davies/research/mycorrhizae.html.