Dryland Crops: The Farmers
Innovator Adds New Summer Crop to Suppress Troublesome Goatgrass
- 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.