There isn’t much you can do to stop a drought.
But you can create your own water to fight a drought by parking the plow, covering your soils and using low-disturbance drills, says Jerry Hatfield, lab director for the National Laboratory for Agriculture and the Environment in Ames, Iowa.
Hatfield told attendees at the No-Till on the Plains Winter Conference earlier this year that no-till systems, paired with adequate soil cover, have the potential to increase water-use efficiency, or the amount of crop produced per unit of water transpired by the crop.
Water-use efficiency has remained relatively constant throughout modern agriculture, he says. But water use tends to increase as yields increase — and with the world’s population expected to increase by 33% in the next 35 years, water deficits may be in the forecast.
Growers can buffer their farm against water shortages, Hatfield says, by changing the soil water balance on their farm.
You can do this by: 1) Increasing the ability of a plant to extract more water from the soil profile; 2) Decreasing soil-water loss through evaporation; 3) Increasing the capacity of the soil to hold more water; and, 4) Changing your cropping system, if possible.
The evapotransporation (ET) rate — soil water evaporation + plant transpiration — is a key term here.
Some components of ET include climate factors growers can’t control, like the sun’s radiant energy, water vapor temperatures and wind speed. But farmers can control the last factor — soil water availability — to some extent with their management practices.
Reducing tillage lowers moisture loss to the atmosphere. Maintaining a residue layer over the soil surface will decrease evaporation by 50-80% compared to a tilled soil, Hatfield says. That’s because standing stubble creates a microclimate near the soil surface that is less conducive to evaporation.
Hatfield noted recent research in a west Texas field where cotton no-tilled into standing wheat stubble showed an increase in water-use efficiency of 30%. Researchers documented larger leaves and more rapid growth because plants were sheltered from the wind, and flowering occurred earlier because of reduced stress.
He also pointed to research by retired USDA soil scientist Don Reicosky that found the use of high-disturbance drills more than doubled the loss of carbon and water from soils when compared to low-disturbance drills.
Differences in soils within a field — likely related to organic matter content and soil water-holding capacity — can create water-use patterns that cause “drought” stress every year, Hatfield says. But some of this variability can be mitigated over time by enhancing soil quality at the field level, he says.
As summer temperatures heat up, growers might want to re-examine how their production system — planting and seeding, soil cover and drainage — affects soil moisture, and identify areas for improvement.
