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Plant Management-Crop Rotation
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By adding commodities such
as corn, small grains, forage and beef cattle to cotton systems,SARE-funded
researchers at Texas Tech University cut water use by 23 percent
and saw higher profits.
Photo by David L. Doerfert |
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Devising an appropriate plant rotation is an effective way to manage
water resources. Since farmers began growing grain in the Great
Plains, they’ve used long periods of fallow to conserve water
for their wheat and other cash crops. The fallow system relies on
the tenet that leaving the land bare over a year or more allows
water to accumulate in the soil.
Farmers now commonly leave crop residues on the surface to protect
the soil. Yet, a number of SARE projects examine crop alternatives
to fallow to achieve better profits and soil benefits while conserving
water.
SARE-funded Montana State University researcher Perry Miller tested
Austrian winter peas as a fall-planted cover crop grown throughout
the winter, the typical fallow. He hoped to prove the nitrogen-building
benefits of the crop, which also provides a second cash crop –
a protein-rich forage for cattle.
Adding peas during the fallow period captures water, guards against
erosion and feeds biomass to the soil. The rotation “is a
much more sustainable practice, and economically positive, too,”
Miller said.
In the Nebraska High Plains, researchers also are testing peas
– as a forage or a grain crop – in wheat systems. Like
the Montana researchers, they are responding to growers who want
to improve their soil management and reduce their fertilizer and
herbicide costs but not deplete soil moisture. Depending on soil
moisture, growers may decide mid-season whether to harvest peas
as a forage, saving 30 percent more soil moisture, or wait and harvest
it as a grain.
Rather than the typical wheat/fallow system that yields a crop
every other year, a team of University of Nebraska researchers are
studying alternative dryland cropping systems with SARE funding.
“As we’ve looked to increase the intensity of the
system – to two crops in three years – this water relations
work has become very important,” said University of Nebraska
researcher David Baltensperger. “We have become very excited
about the potential for cool-season, short-growth crops that use
less water and allow more time to accumulate water prior to planting
wheat to replace fallow in the High Plains.”
Baltensperger’s colleague, Drew Lyon, has developed a flexible
dryland cropping system that encourages producers to decide whether
to plant a short-season crop or stay in fallow based on soil moisture
availability just before planting. Some growers are planting cool-season
oil crops such as brown mustard, canola and camelina, whose seeds
are crushed for biofuel. The seeds contain 20 percent more oil than
soybeans.
“They are short-season crops with most of their growth in
the cool-season, high-rainfall period, with tremendous market potential,”
Baltensperger said.
Cotton is a significant water-user. In Texas, about one-quarter
of the total U.S. cotton supply comes from the state’s High
Plains region. Yet, water levels are declining in the Ogallala aquifer,
the main water source for northern Texas growers. Scientists such
as Texas Tech University researcher Vivien Allen are seeking water-conserving
alternatives to monoculture cotton.
Armed with a SARE grant, Allen developed an innovative cotton,
cattle and forage rotation that reduced water use by about 23 percent.
Of great interest to farmers, that system – which features
the perennial, drought-tolerant forage old world bluestem –
also doubles profitability. The forage, seeded in half of the alternative
plot, required no irrigation for five months of the year, driving
down average irrigation over four years to 372 mm compared to 481
mm in the continuous cotton system.
In early the 1900s, when Texas farmers began drilling wells into
the Ogallala aquifer, cotton proved a reliable, profitable crop.
As water levels in the Ogallala drop, however, cotton farmers face
a few tough choices: run out of water, drill deeper and extract
water at greater cost, or diversify. Much of the High Plains region,
including parts of Nebraska, Colorado, Wyoming, Oklahoma, Kansas,
New Mexico, South Dakota and Texas, relies on the Ogallala for water.
“When we began to irrigate, we took a 10-million-year-old
resource and virtually expended it in 100 years,” Allen said.
“We need a cover on the land because of erosion, and that
cover needs water.”
Allen’s new rotations were so promising that Allen and her
management team won a $6.2 million state grant to demonstrate water-conserving
farming strategies across the Texas High Plains. Responding to public
interest in the dropping water level in the Ogallala aquifer, Allen’s
team, the Texas Alliance for Water Conservation, is using the opportunity
to further test those systems across 4,000 acres on 26 farms and
ranches. Under the state project, producers will test diversified
systems and the conservation team will measure their water use.
For instance, some farmers will rotate pasture grasses with cotton
for forage or grazing; others will over-seed cool-season cereal
crops into cotton for eventual harvest.
“The declining aquifer greatly affects us,” said Monty
Dollar, an NRCS conservation agronomist and member of Allen’s
team. “Irrigation water is instrumental in producing profitable
yields that sustain our operations. Yet, we’ve got to learn
to live with less water. We’re going to find out if we can
do that.”
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