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Dryland Crops: The Farmers
Innovator Adds New Summer Crop to Suppress Troublesome
Goatgrass
Grant Smith
Lehi, Utah
 11,000
acres, flat-land
hard
red winter wheat, safflower
fallow
system on mulch-till land
soil
types: clay-loam; some sandy clay-loam
12 inches
annual precip.; 6- to 18-inch variation, mostly spring
weeds:
jointed goatgrass, Russian thistle, wild shiny lettuce
Weed management highlights
Strategies: fallow cultivation... crop rotation with summer
annual
Tools: chisel plow... tandem disk... rod weeder
Jointed goatgrass, like the tares of Biblical times, grows right up with a
wheat crop. Seeds from the tenacious invader traveled with seed wheat for several
seasons in the 1980s before northern Utah farmers realized they had a serious
threat in their fields.
During the same time, Grant Smith joined many ranchers in experimenting with
no-till wheat. They wanted to till the soil less, squeeze in an extra crop with
less land in fallow, and make a little more profit.
They hoped to find a management option in a dryland farming situation that
presents them with few other cropping alternatives. But surging goatgrass and
declining rainfall combined to confound the plan and spurred Smith to look for
a new spring crop. Since the new grass weed has become established, mechanical
tillage is again a necessity. “If I use no-till every year, the goatgrass population
explodes. So we’re working to keep it down.”
Researchers say as few as two plants of the grass per square foot can reduce
yields of winter wheat by 30 percent. Each plant can produce from 80 to 600
seeds, with the final 1 percent of seeds staying viable through the fifth year
in the soil.
Even before goatgrass arrived, one of Smith’s favored techniques was to plant
barley as a weed-fighting rotation crop. The spring-planted grain followed wheat,
which he harvests in July or August. About half the time, post-harvest weed
pressure in wheat is intense enough to require a pass with his 48-foot Chisel
Plow. Excess stubble and volunteer wheat seedlings can also prompt
the cultivation. He uses 2-inch straight points on 12-inch centers to create
a rough, snow-trapping surface.
When he plants a summer crop, he chops up the first flush or two of weeds with
his 33-foot tandem disk.
The disk’s smooth, 24-inch blades on 9.25-inch spacing are effective
in dealing with heavy residue or large weeds.
He starts weed-controlling tillage as early as possible in March and April.
His goal is to clean the fields, incorporate residue and open up the soil to
capture anticipated spring rains. As soon as a seedbed is ready with sufficient
moisture, he plants.
To pay its way, barley needs the equivalent of at least several inches of rain—stored
in the soil or fresh from the sky—by the time it reaches boot stage in mid-June.
Summers with barley-safe moisture levels began tapering off about a decade ago,
just as the goatgrass began take up residence.
So he tried a new summer crop that would compete with the goatgrass and allow
fall tillage to knock out the weed’s new seedlings. Smith pioneered the use
in Utah of safflower, an oilseed, as a more drought-tolerant summer crop. The
plant resembles a small, bushy sunflower with a yellow blossom, prickly stems
and a vigorous taproot system.
Following a final light disking, Smith drills in safflower. After trying many
rates both higher and lower, he says 25 pounds of seed per acre gives the most
dependable, cost-effective stand. If weed pressure is high, he uses a pre-plant
incorporated broad spectrum herbicide.
Safflower develops slowly at first, when weed control is most critical. Its
bushy leaves provide late-season weed control. The final result is usually weed
pressure similar to wheat, he says, but with a suppression effect on goatgrass.
He uses the wheat head on his combine to harvest safflower in October and hopes
for a yield of 1,000 pounds per acre. Net profit per acre is a bit lower than
for wheat, but the second crop serves a valuable weed-fighting role. He rotates
the summer annual break in the wheat-fallow-wheat rotation to all his fields.
He treats the harvested safflower fields the same as wheat lands, tilling just
enough to control weeds through the following winter and summer fallow seasons.
He’s also used herbicides to control weeds on summer fallow. The practice preserves
enough moisture to allow him to skip the fallow season in alternate years when
there is sufficient soil moisture.
“You can get an extra crop, but yield drops,” he says. He’s waiting for wetter
fall seasons and good weed control before trying back-to-back wheat again. Smith
manages about half of his acreage—“the better land”—in a wheat-safflower-fallow
rotation, with the balance in wheat-fallow.
Fallow weed management starts in April with the chisel plow. This time he outfits
it with 16-inch sweeps on the curved, solid shanks that run 1 foot apart. He
runs the sweeps 4 to 6 inches deep, the same depth as the fall passes with the
chisel points.
“I travel about six miles per hour when I’m chiseling. No faster,” says Smith.
“Higher speed makes the sweeps harder to keep in the ground and harder to drive
straight. Plus it’s harder on equipment.”
He comes back to the fallow fields with the tool when weeds rebound in June,
then again in late August or early September. Some seasons take as many as four
passes. Smith knocks down the weeds while keeping all the residue he can on
the surface. He raises the sweeps about an inch each time to bring the subsoil
moisture zone closer to the surface in anticipation of fall wheat planting.
He runs his 64-foot Leon rod weeder
if he needs a final pre-plant weeding pass. The implement is a ground-driven
model with a round rod that spins just beneath the soil surface.
Smith feels the square rod used in the 1930s did a better job of
weeding. Maintenance of drive sprockets and chains is important,
he says, as is keeping speed below 4 mph to prolong tool life and
avoid downtime.
Smith approached his 1997 season with confidence that he has a good weed management
system in place. He feels it’s one that will work just as well when “normal”
precipitation returns as it has during the past seven years of drought. But
like other good farmers, he’s still looking for better ways to hold back weeds
and give his crops the advantage.
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