Mix No-Till and Rotations to Store More Precipitation
Scientists at the USDA–Agricultural Research Service Central Great Plains Research Station in Akron, Colo., are in the 20th year of a major project to determine which alternative crops farmers could use to eliminate—or at least reduce the frequency of—fallow fields.
The Alternative Crop Rotation project compiles data from four full four-year rotation cycles, allowing scientists to average out the effects of weather for parts of Colorado, Kansas, Nebraska and Wyoming.
USDA–ARS soil scientist Merle Vigil and his colleagues are using wheat, corn, millet and fallow in four-year, three-year and two-year rotation cycles to evaluate crop production and water-holding capacity of crop rotation systems.
Vigil says storing water in just the top inch of an acre of land (an “acre-inch”) is worth $25 to $30 per acre. This calculation uses 10-year average crop prices, relating crop yields to stored water levels.
Four to six tillage passes to kill weeds on fallow resulted in a loss of 3 acre-inches of water during the course of 14 months. Those tillage passes cost $24 to $48 an acre in fuel and labor. “Adding that to the cost of water lost, that’s $99 to $138 from your pocket,” Vigil says.
Using no-till practices in conventional wheat–fallow rotations can increase net farm income, and combining no-till and no-fallow practices can capture more precipitation in various parts of the Central Plains.
With one of the most profitable rotations, no-till wheat–millet, farm net income could increase $1,300 a year compared with no-till wheat–fallow on a hypothetical 160-acre farm used for economic analyses.
Although less fallow is good, the other three best rotations (wheat–millet–fallow, wheat–corn–millet–fallow and wheat–corn–fallow) still incorporate fallow in the rotation, meaning it might not yet be practical to totally eliminate fallow.
“The idea is to store precipitation in the soil during the idle months,” Vigil says. “Today it is not economically or environmentally sustainable for most soils in the region.” Fallow loses 65% to 80% of soil moisture to evaporation, causes a decline in soil organic matter and gives low economic returns.
“Since no-till retains more water, it permits increased cropping intensity from one crop in two years to three crops in four years—and in some cases, continuous cropping with no summer fallow,” Vigil says.
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