Amarillo, Texas
October 4, 2005
Ground left fallow in the High
Plains to store soil moisture between crops may be better off
with a legume crop such as cowpeas, according to a
Texas Agricultural
Experiment Station researcher.
Dr. Bill Payne of Amarillo said he is trying to make the
region's wheat-sorghum-fallow cropping system more sustainable
by getting rid of the fallow component.
Leaving the land idle for one cropping season is a way to retain
soil moisture for the following crop. However, Payne said, this
practice doesn't store that much moisture. And it oxidizes the
soil organic matter, leaving the land subject to erosion and
releasing carbon into the air, thereby contributing to global
warming.
Planting a legume crop, such as cowpeas, allows the producer
three crops in three seasons, rather than two crops in three
seasons, he said.
The residue from the cowpeas also adds organic matter, which
tends to decompose faster than cereal crop residue, Payne said.
"What we'd like to do is plant it the year after sorghum and
before fall-planted wheat," he said. "What we're trying to do
now is find the right maturity group among cowpea varieties."
Cowpeas can be grown in as little as 65 days, allowing for a
brief fallow period before the wheat is planted. A longer-season
variety can go until a killing frost, Payne said. The research
is aimed at finding a balance between biomass production and
water conservation, he said.
"The options would be to hay it or graze it as a forage, or if
there's a market for the peas, a producer could go for that,"
Payne said.
The crop can be harvested at flowering for forage and at pea
production, as with blackeyed peas. By doing both, he can
compare water usage and determine potential water stress on the
next crop.
"Our hope is the wheat yields will increase following cowpeas,
as well as the sorghum," Payne said. "We see that in other parts
of the world, but here we have to be careful of the water
component."
Preliminary data shows the more cowpea biomass produced, the
larger the yield increase of the following cereal crop, he said.
However, the study must run for at least six years or two entire
crop rotations to confirm the results.
Determining the sustainability characteristics -- changes to the
soil physical and chemical properties -- will take even longer,
he said.
"We can show now that growing cowpeas results in less soil water
storage at wheat planting than fallowing," Payne said. "But so
far, it has been such a small amount, it's insignificant as far
as yield goes."
Cowpeas' water requirements depend on the maturity group, but
the goal is to find a variety that will survive on 12 inches of
rainfall, he said.
During 2003's dry growing season, Payne said, the sorghum died
off before the cowpeas, which means cowpeas is a very drought
tolerant crop.
Payne said some experts are concerned that cowpeas grown on any
significant scale in the U.S. would flood the human consumption
market and lower the price. However, as forage, cowpeas shows a
lot of potential, he said.
In Africa, tests show cattle's weight gain doubles when cowpea
fodder is added to their diet, Payne said.
"I think producers are looking for a high-protein forage crop,"
he said. "There's a reason cowpeas are called 'cow' pea. Earlier
on, cows grazed it throughout the South."
The protein value of cowpeas ranges from 22 percent to 30
percent, Payne said.
"We'll have to work with producers and (Texas Cooperative)
Extension agents to see how it works into a production system,"
he said. "Timing of pasture availability will be important. We
want to try to time its availability with the greatest demand,
so there are still things to work out." |