COLBY, KANSAS, U.S. — A Kansas State University (KSU) study indicates that continuous cropping increases the percentage of precipitation that can be used by wheat.

In the first stage of an ongoing study, KSU research crop scientist Rob Aiken found evidence that fallow helps “drought-proof” the farms in western Kansas. He also found that increasing crop intensity by going to continuous cropping, the amount of precipitation available for crop production was increased, but less grain was produced.

“The wheat-fallow system accumulates water over a two-year period, producing a single wheat crop,” said Aiken, who is based at KSU’s Northwest Research-Extension Center in Colby, Kansas, U.S. “Farmers really picked up on this in the ‘Dirty 30s.’ It’s a long-standing cropping practice for good reason.”

Tillage provides weed control but often leaves soil exposed, which can promote evaporation and erosion. Frequently, 80% or more precipitation is lost to evaporation during a fallow period, he said.

“With fallow, we’re not very effective in storing water,” he added. More intensive crop sequences use feed grains and oilseeds to reduce the fallow periods and increase crop access to precipitation.

“Our objective with the study was to compare water use, grain yield and biomass productivity for 10 cropping sequences, which all included winter wheat,” Aiken said. Corn or grain sorghum feedgrains were included in nine of the crop sequences; six sequences were cropped continuously by including an oilseed crop – spring canola, soybean or sunflower.

“Our results in the first stage (2002-07) showed that by increasing crop intensity, going from wheat-fallow to continuous cropping, we nearly doubled the amount of precipitation available for crop production,” he said.

The difficulty, he said, is that despite increased precipitation, crop water productivity dropped from 221 pounds per acre inch to 145 pounds per acre inch. So the message is to proceed with care with continuous cropping.

Initial study results for the period 2002-07, which included a three-year drought, indicated several trends:

  • Land productivity varied with rainfall among years;
  • Wheat productivity benefitted from summer fallow;
  • Grain sorghum productivity exceeded corn when limited by water;
  • Continuous cropping increased the percentage of precipitation which could be used by a crop, but reduced overall land productivity; and
  • Stand establishment, timing, and amount of water limited oilseed productivity.