Stubble can be managed to conserve soil moisture. In the brown soil zone, tall stubble has proven to be a practical snow management tool.
A study was started in 1993, at a site south of Acadia Valley, Alta., to compare tall stubble from direct combining, short stubble from swathing and alternate height trap strips in a durum wheat-fallow rotation.
“The alternate height trap strips, made by direct combining the crop at two different stubble heights, showed no advantages in snow accumulation, soil moisture gain or crop yield,” said Allan Howard, soil moisture specialist with Alberta Agriculture in Lethbridge.
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“Tall stubble showed the best combination of snow trapping and soil moisture conservation. The short stubble, while not as effective in snow trapping, had overwinter soil moisture gains that were similar to the tall stubble.
“The short stubble treatments had the cut straw chopped and blown evenly over the soil surface, creating a mulch that reduced evaporation. There was no direct effect of the treatments on crop yield.”
The results suggest that in the brown soil zone, where snowfall is limited, residue management such as direct combining and well-chopped, evenly spread straw effectively conserve moisture.
Trap strips may be best used under special conditions, such as lodging, where stubble must be cut very short.
A new treatment was added in 1996 to examine the effect of baling and removing straw from short stubble. Preliminary results suggest that when there is no straw mulch, less moisture is conserved.
“The study is planned to continue at least through the year 2000,” Howard added.
The timing of spring snows and rains, fall moisture content, and surface runoff during snowmelt all influence overwinter soil moisture gains.
In this study, wet fall soils were present in two of the four years, and a late spring snow following ground thaw happened in another year. These reduced the differences between treatments.
To fully assess the treatments, data from several years must be evaluated.
A study was initiated by the Chinook Applied Research Association, the M.D. of Acadia, Alberta Agriculture and Farming for the Future.
