What's more, kenaf can also be
processed into acoustic tile, cat litter, bedding for horses or other animals,
composite board for construction, mats for erosion control and grass seeding,
or pads for cleaning up chemical or oil spills.
Canola, a member of the mustard family, yields a healthful vegetable oil.
Forage made from the crop is a desirable feed for farm animals because it has
about as much protein as alfalfa, a premier forage and hay crop. And canola
plants first used to cleanse or detoxify high-selenium soil or drainage water
might next be sold as a value-added feed for livestock in regions where soils
don't provide enough of this nutrient.
"In the United States, selenium deficiency is typically a bigger
problem than selenium toxicity," says ARS soil scientist Gary S.
Bañuelos. "Selenium deficiency is a major problem for livestock or
wildlife in at least 37 states and costs beef, dairy, and sheep producers an
estimated $545 million in losses every year. Ranchers in selenium-poor regions
either inject their animals with the mineral or add selenium supplements to
Bañuelos, who is with the ARS Water Management Research Laboratory in
Fresno, California, has not only scrutinized selenium uptake by kenaf and
canola, but has also looked at the selenium-recycling prowess of other
cultivated crops, including grasses, legumes, and even vegetables like
broccoli, cabbage, Swiss chard, and collard greens. And he has investigated the
ability of wild plant species like Indian brown mustard to suck selenium from
The site of these experimentsCalifornia's central valleyis
America's number one agricultural region. Ironically, growers there struggle
with an overabundance of selenium on the west side and a paucity on the east.
Feeding Canola to Livestock
In collaboration with ARS soil scientist Henry F. Mayland at Kimberly,
Idaho, Bañuelos examined the effects of feeding selenium-enriched canola
to lambs and dairy cows. Grower John E. Diener of Red Rock Ranch in Five
Points, California, produced canola for the experiment.
"Of course it's too early for us to recommend feeding of
selenium-enriched hay to livestock," cautions Mayland. "But these
preliminary results look promising."
The study was likely the first to use, as an animal feed or supplement,
canola that had been grown specifically for the task of pulling naturally
occurring selenium from the soil.
Half the animals in the tests were fed canola that had been irrigated with
high-selenium drainage water (200 to 500 parts per billion). Water for
irrigating the canola fed to the other lambs and cows had only 10 parts per
Ten lambs nibbled freshly harvested canola for 7 weeks; eight dairy cows ate
dried, coarsely ground canola as part of their total rations for 20 days. The
amount of selenium in canola was meticulously measured to make sure it was at a
safe levelless than 5 milligrams per kilogram of dry matter. That's the
equivalent of about a small pinch of selenium in a bale of hay.
The scientists also checked selenium levels in blood, cow's milk, and other
samples. "All of the animals," reports Bañuelos,
"remained healthy throughout the study. None showed signs of getting too
much selenium from the canola."
An added bonus: An informal taste test of milk produced by the canola-fed
cows indicated no detectable difference in flavor. Plus the animals' weight
gainsessential to ranchers' profitswere about the same, regardless
of the selenium content of the feed.
But what about the selenium that ends up in the manure of animals that eat
higher-selenium canola? Results from an earlier ARS study suggest that
dangerously high levels of selenium are unlikely to cycle into pasture plants
from the manure. That means the plants should still be safe for animals to
Selenium in cattle manure is predominantly of the organic forms that are
less available to plants than the inorganic forms. That's according to an
earlier experiment reported by Husein A. Ajwa at the Fresno lab, along with
Bañuelos and Mayland. They used potted canola and tall fescue plants
grown in soils treated with manure or other selenium sources.
For the selenium-recycling study with kenaf, Bañuelos and
co-researchers grew some 120,000 plants on a 1-acre site near Los Baños,
California. He did the kenaf analysis in collaboration with Patrick T. Treffey
of 3-Way Farms, Watsonville, California; Charles G. Cook, formerly with ARS;
and David A. Dyer of USDA's Natural Resources Conservation Service.
The hardy plants shot up nearly 15 feet in only about 6 months.
"Kenaf," says Bañuelos, "took up at least 25 percent of
the soluble selenium to a depth of about 3 feet. Canola, which has shallower
roots, used about 50 percent of the selenium to a depth of about 2 feet."
Though kenaf is less tolerant than canola of very salty drainage water, that
doesn't take this plant out of the running. "Irrigation wastewater that's
high in selenium," Bañuelos says, "isn't always overloaded
with other salts. Besides, kenaf plants rapidly produce a tremendous amount of
biomass, meaning that in a very short time you have a very big plant cleaning
up a lot of soil and water for you."By
Marcia Wood, Agricultural
Research Service Information Staff.
This research is part of Water Quality and Management, an ARS National
Program (#201) described on the World Wide Web at
Gary S. Bañuelos
and Husein A. Ajwa are in the
USDA-ARS Water Management
Research Unit, 2021 S. Peach Ave., Fresno, CA 93727; phone (559) 453-3100,
fax (559) 453-3122.
Henry F. Mayland
is at the USDA-ARS Northwest Irrigation
and Soils Research Laboratory, 3793 N., 3600 E., Kimberly, ID 83341; phone
(208) 423-6517, fax (208) 423-6555.