
"Robin Hood" Fungus Presents
Agricultural Dilemma By Jill Lee November 13, 1998A fungus that transfers nutrients
from the soil to plants roots seems like a blessing from Mother Nature.
But a type of fungus known as mycorrhizae will feed any needy plant, including
sicklepod and other weeds, according to scientists at the
Agricultural Research Service. Most soybeans form nodules, or small knobs, on their roots. Beneficial
bacteria that live on the nodules draw nitrogen from the atmosphere. But a
genetic mutation can prevent some soybean varieties from forming the nodules.
These non-nodulating plants have now supplied new clues for scientists at ARS,
the U.S. Department of Agriculture's chief
scientific agency. Since the 1970s, researchers have noticed that a row of nodulating soybeans
will share nitrogen with a neighboring row of non-nodulating plants. The closer
the two rows are, the taller and healthier are the non-nodulating soybeans.
Scientists have also suspected that mycorrhizae can play an important role in
nutrient uptake by plant roots. ARS agronomist Joe Burton in Raleigh, N.C., tied these two facts together by
chemically tracing the path of nitrogen between crop rows. The nodulating
plants themselves are not being charitable. Instead, Burton found,
mycorrhizae were busily transporting nitrogen away from the nodule-producing
rich plants to the non-nodulating poor ones. What does this mean to farmers? They dont grow non-nodulating
soybeans; the nitrogen-fixing nodules make for high-protein soybeans. The
question: where else might the mycorrhizae take that extra nitrogen? The
answer: sometimes to weeds--including sicklepod, Palmer amaranth and
morning-glory, the scientists have learned. Because mycorrhizae are probably beneficial for acquisition of all soil
nutrients, getting rid of the helpful microbes is not desirable, even if it
were possible. Now that agricultural researchers have demonstrated the mycorrhizaes
indiscriminate generosity, they will be exploring ways to make it shun sharing
nitrogen with weeds. Scientific contact: Joseph W. Burton, ARS
Soybean and
Nitrogen Fixation Laboratory, Raleigh, N.C., phone (919) 515-2734, fax
(919) 515-7959, [email protected] U.S. Department of Agriculture | |