Beneficial soil fungi exhibit a symbiotic link

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LAMARTINE

During the growing season, major attention is given to what's happening to plants above the ground, including any threats from pests and diseases, but this view fails to consider the activities below the soil surface during that time and throughout the year.

That was the “From the Ground Up” message from Loretta Ortiz-Ribbing to attendees at the annual agronomy field day held at Montsma Farms with sponsorship by Country Visions Cooperative and the Fond du Lac County Forage Council. In June of this year, she became an Extension Service crops and soils agent with a 50:50 shared appointment in Fond du Lac and Dodge counties.

Plant Root Interactions

The roots of major crops such as corn and soybeans and other vascular species enjoy a symbiotic association with a few of the beneficial soil fungi, particular the mycorrhizae, Ortiz-Ribbing pointed out. She explained that the mycorrhizae, which are much smaller than root hairs, nonetheless create long threads in the soil that can carry water and nutrients to the plants, certainly helping the plants during times of stress related to the weather, pests, and diseases.

In turn, the health of the mycorrhizae (technically “arbuscular mycorrhizal fungi”) depends greatly on the carbon that the living plants supply from the surface, Ortiz-Ribbing observed. What needs more awareness is that the longer there is a living organism above the soil surface, the better it is for the mycorrhizae, she stated. “They will go dormant if there is no association with a plant.”

That association does not apply to such species as radish, spinach, canola, lupins, sugar beets, mustards, sugar beets, cabbage, turnips, cauliflower, and other members of the brassica family, Ortiz-Ribbing indicated. But 70 percent of the plant species have such an association with the mycorrhizae, she noted.

Although farmers may till soil for legitimate reasons, they should also realize that tillage will destroy the threads of the mycorrhizae, Ortiz-Ribbing warned. Until the mycorrhizae have a chance to recover, plants will be deprived of a portion of their access to water and nutrients stored in soil pores beyond the reach of their roots, she explained. Another benefit of mycorrhizae is the production of glomulin, which is a soil binding protein, she added.

Allelopathic Species

Ortiz-Ribbing also shared some observations about species which have allelopathic traits that can affect the growth of other species or even soil-borne pathogens. She referred to research on that point at the University of Illinois at Urbana-Champaign, where she obtained three academic degrees.

One of those studies found a correlation between ryegrasses and rapeseed for controlling the presence of rhizobacterial root rot in soybeans, Ortiz-Ribbing reported. She said that canola and mustards can have a similar effect.

A surprise in the Illinois field studies was a great reduction in soybean cyst nematode eggs after canola, rapeseed, or cereal rye were grown on the sites, Ortiz-Ribbing observed. For those and other reasons, the benefits of growing cover crops or diverse species should not be overlooked, she advised.

Ortiz-Ribbing can be reached by phone in the Fond du Lac office at (920) 929-3171 or (920) 386-3790 in the Dodge County office. Her cell phone is (920) 296-5293. The e-mail address is Loretta.OrtizRibbing@ces.uwex.edu.

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