Ethanol Byproduct Fights Weeds, Boosts Crop
The Tomato Magazine
Distillers dried grains (DDGs) are the leftovers from converting
corn into fuel ethanol, a cleaner burning alternative to gasoline. In
the Midwest alone, ethanol producers generate 10 million tons of DDGs
annually. Farmers buy the stuff for between $85 and $110 a ton and feed
it to livestock.
Soon, though, growers may be spreading it on their crop fi elds to cut
down on herbicide use. Some DDG extracts may even find health-food uses.
Several ARS scientists certainly hope so, since U.S. ethanol production
is expected to climb from 4.4 billion gallons annually to 7.5 billion
by 2012. Thatll mean even more DDGs and other byproducts.
Through laboratory, greenhouse, and field experiments, the researchers
have shown that using DDGs as mulch not only suppresses weeds, but also
bolsters growth in tomatoes and some turfgrasses.
Steven F. Vaughn, a plant physiologist with ARSs National Center
for Agricultural Utilization Research (NCAUR) in Peoria, Illinois, notes
that DDGs worked best when incorporated into the soil and left to decompose
for a few months.
DDG mulch applied in this manner promoted Kentucky bluegrass growth
while inhibiting seed germination of annual bluegrasswhich is considered
a weed, he says. Similarly, Vaughn applied DDGs to Roma tomato plots
in November 2005, at rates of 1, 2, and 3 kilograms per square meter,
and transplanted the crop in early May. At the end of September, the yield
was 226 pounds of tomatoes from plots treated with the lowest rate of
DDGs and 149 from control plots, which received no DDGs. Nitrogen, phosphorus,
and other nutrients from the decomposing mulch probably contributed
to much of that yield increase. At the higher DDG rates, however, plants
grew large but did not yield as much fruit as the low-DDG plants did.
Thats a symptom of too much nitrogen, Vaughn points out.
Weed-seed inhibition is a bit more complicated, adds Mark
A. Berhow, an NCAUR chemist. Using various analytical methods, hes
trying to identify, measure, and monitor the yearly fluctuations of DDG
chemicals that may have inhibited germination in crabgrass, chickweed,
annual rye, and other weeds studied.
So why wasnt growth of the tomato plants inhibited? One possibility
may be that they were planted in the treated plots as seedlings rather
than as seed, which may be more sensitive to the mulch, Berhow says.
The situation was a bit different for potted ornamentals. Transplanted
plugs of rose, coreopsis, and garden phlox benefited from the DDG mulchs
suppression of chickweed and other weedsbut only when it was applied
to the soils surface. When mixed into potting soils, DDGs
were toxic to the ornamentals, reports Rick A. Boydston, an agronomist
with ARSs Vegetable and Forage Crops Research Laboratory, Prosser,
Besides weed inhibition, Berhow is examining DDGs for phytosterols (added
to some margarines), lecithin, and other health-promoting substances.
Antioxidants are of particular interest for their ability to
neutralize cell-damaging molecules called free radicals.
NCAUR chemist Rogers E. Harry-Okuru is examining processing methods
for removing economically important materials from the DDGs, such as phytosterols
and oil (DDGs are about 10 percent corn oil by weight), which can be made
Vaughn, meanwhile, plans on expanding the turfgrass studies. Hell
also try the mulch with Swiss chard, a relative of beets whose leaves
may flourish with the added nitrogen. ARS has applied for a patent on
the mulch and is negotiating terms for the scientists to collaborate with
an Illinois-based turfgrass company.
Editors Note: This research is part of Quality and Utilization
of Agricultural Products, an ARS National Program (#306) described on
the World Wide Web at www.nps.ars.usda.gov. To reach scientists mentioned
in this article, contact Jan Suszkiw, USDA-ARS Information Staff, 5601
Sunnyside Ave., Beltsville, MD 20705-5129; phone (301) 504-1630, fax (301)
504-1486. DDGsEthanol Byproduct Fights Weeds, Boosts Crop
Yields was published in the May/June 2007 issue of Agricultural
© 2007 Columbia
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