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Cropping Every Acre
In the semiarid high plains of western Nebraska, moisture is as good as gold. Thirteen to 15 inches of precipitation is the best that wheat growers can expect to get in a year. Hoping to store skimpy moisture in the soil, many growers continue to rotate winter wheat with summer fallow – either tilled or chemical.
Given such dry growing conditions, straying from the summer fallow takes some courage and a willingness to risk crop failure. Wheat grower Alton Lerwick, Harrisburg, Nebraska, had both back in 1974 when he came home from college to start farming with his father, Melvin.
“Like other farmers around us, we alternated winter wheat with tilled summer fallow,” says Alton Lerwick. “We had a lot of wind erosion, though, and I couldn’t tolerate it. I couldn’t stand to see that topsoil blowing away. In the summer, we had water erosion.”
Melvin gave his son the freedom to experiment with alternatives. The first change they made was to switch to reduced tillage, which kept more residue on the soil surface.
Then, in the 1990s the Lerwicks eliminated tillage completely by going to a no-till system.
“By 1997, I was convinced I could grow a crop on every acre,” says Lerwick. “Having that as a goal forced the need to find other crops that would grow well for us and then build a diverse rotation from these. The system we have since devised has worked well, and it has eliminated wind erosion.”
On top of that, soil health has improved, and both yields and profitability have increased. Wheat yields have surpassed the county average, and overall land productivity has more than doubled in comparison with what it was with a wheat-fallow rotation.
Today, as Lerwick farms now with his own sons, Dean and Grant, they grow four crops in a continuous-cropping rotation. Behind winter wheat comes corn, then confectionary sunflowers, and finally, proso millet.
While running out of soil moisture might have been a concern in the early years of Lerwick’s experiment with no-till and continuous cropping, the system has proven instead to actually improve efficiencies of moisture storage and use.
Following are three contributing factors.
- Surface residue traps moisture.
“Snowfall contributes a significant amount to our annual moisture,” says Lerwick. “The stubble fills up with snow, and then a chinook wind comes along and melts it. That gives the stubble an opportunity to fill back up when another snowfall comes.
The surface residue holds the snowmelt from running off, and increasing water infiltration in the soil permits moisture to percolate downward.
- Organic matter has increased.
“In our previous wheat-fallow rotation, we were mining the soil organic matter for the release of nitrogen,” says Lerwick. “Back then, we had some soils that tested less than 1% in organic matter. Over a period of 10 years of no-till and continuous cropping, some of our soil tests show organic matter levels as high as 2.5%.”
Lerwick’s testing of organic matter (OM) in native sod also shows levels of 2% and 2.5%. This could suggest his soils may be approaching their native capacity for OM.
The higher levels of OM in Lerwick’s soils result from continuous cropping paired with no-till. “With just no-till alone, we didn’t see the increases in soil quality until we started growing a crop on every acre every year,” he says. “By growing a crop, we produce more root material and more surface residue, and that breaks down and becomes more organic matter.”
- Soil structure enhances water infiltration.
As OM increases, soil becomes more biologically alive. Root channels and stable soil aggregates enhance soil porosity, permitting improved water infiltration. Stable soil aggregates also are effective at storing water.
“Visually, the soil structure is improving,” says Lerwick. “The soils are crumbly and don’t have the plating that’s characteristic of a layer of compaction. The soil is also full of earthworms.”
Feeding the overall cropping system with sufficient crop residue is an ongoing challenge. As the soils become more biologically active, the breakdown of residue speeds up. Because of that, Lerwick will grow only one low-residue crop in four years.
While sunflowers are a highly profitable crop for the family, they consider the sunflowers to be low-residue producers. Because of that, the Lerwicks will grow them only once in four years.
For that same reason, they have not yet worked a legume into the rotation. “A legume would benefit the soil microbiology, and we’re experimenting with growing field peas, lentils, and garbanzo beans,” says Lerwick. “They tend to be low residue, though, so we’re considering carefully how we might work them into the rotation.”
To conserve as much residue as possible, the Lerwicks harvest crops with stripper headers. They leave all wheat stubble standing rather than harvesting some as straw bales.
Lerwick never counted on the multiple benefits of building a diverse no-till system. “We started out simply trying to stop wind erosion,” he says. “We didn’t realize we would end up here – with improved profitability, better soil quality, and habitat for wildlife.”
Quality of life has improved, as well. “I used to spend the summer tilling fields to fight weeds,” he says. “Now, I spend much of my time in the summer walking the fields, scouting for problems. It’s more pleasant to simply watch things grow, rather than stop things from growing.”
more than doubling productivity
When Alton Lerwick began growing a crop on every acre, productivity automatically increased. It grew even more as soil health improved, generating higher yields.
Randy Anderson, agronomist at the USDA-ARS North Central Agricultural Research Laboratory at Brookings, South Dakota, compiled just how much productivity had improved.
“To compare land productivity between continuous cropping on the Lerwick farm and a winter wheat-fallow [rotation in his county], we calculated annualized yield by adding yields of all crops in a rotation for a given year, and dividing by the number of years in the rotation,” he says.
During the period of 2008-2015, average yields in Lerwick’s continuous cropping system tallied 29 bushels per acre for winter wheat, 51 bushels for corn, 1,320 pounds per acre for sunflower, and 33 bushels for proso millet. Winter wheat yield after fallow in Lerwick’s county was 24 bushels.
“Continuous cropping produced 1,770 pounds per acre of grain product per year, while only 660 pounds of grain product was harvested from winter wheat-fallow,” says Anderson. “Continuous cropping increased productivity 2.7 times compared with winter wheat-fallow.”