Questions often arise among no-tillers concerning the best height at which to leave small grain stubble. At the Semiarid Prairie Agricultural Research Centre at Swift Current, Saskatchewan, Canada, researchers set out to find answers by no-tilling four spring crops into three residue combinations.
Four Crops, Four Stubbles
They no-tilled spring wheat, lentils, field peas and chickpeas into cultivated stubble, 6- to 7-inch spring wheat stubble and 10- to 16-inch-tall spring wheat stubble. The plots were left in place over the winter to equalize snow trapping effects.
“Standing stubble changed the microclimate near the soil surface by reducing soil temperatures, solar radiation, wind speed and potential evapotranspiration,” says researcher Brian McConkey. “Standing stubble effects on microclimate continued well beyond the time when taller crops grew above the stubble. These effects were more pronounced for tall vs. short stubble.”
The researchers found the four crops grew 2 to 3 inches higher with the tall stubble. Even the lowest pod height was still as much as 3 inches higher with the tall stubble than with the cultivated stubble.
McConkey says crop water-use efficiency increases as stubble height rises. The only exception was with chickpeas where both yield and crop water usage appeared to decline in tall stubble. This may be due to shading effects on the relatively small chickpea canopy that never grew past the height of the tall stubble.
Compared with cultivated stubble, yield results were as follows:
• Spring wheat—6 percent higher for short stubble and 12 percent more for tall stubble.
• Chickpeas—10 percent higher for short stubble and 5 percent higher for tall stubble.
• Field peas—9 percent higher with both short and tall stubble.
• Lentils—12 percent higher for short stubble and 21 percent higher for tall stubble.
The researchers found tall stubble significantly reduced the amount of water loss compared with cultivated and short-stubble treatments. There was a tendency to reduce water losses with the short stubble compared to tilling the stubble.
The researchers also found the average daily wind speed was much less with tall stubble when it was measured at a 6-inch height.
Under 6 inches, tall stubble reduced wind speed by 70 percent and short stubble reduced wind totals by 15 percent compared with cultivated stubble.
Prior to the 3 1/2-leaf stage, the daily total amount of incoming solar radiation was lowest for the tall stubble when measured at 3 inches. Soil temperatures also decreased with stubble height.
Stubble Pros And Cons
While production within tall cereal stubble was beneficial for increasing spring-sown crop yields in a water-limited environment, the method could be detrimental under some circumstances.
For example, a more humid environment within standing stubble increased both leaf and stem diseases in Montana research trials. Under wet conditions, tall stubble might slow soil drying enough to delay seeding. The shading effect of the stubble might limit yields for crops that never outgrow the stubble.