Burning the midnight oil to finish seeding might pay off in more ways than one, according to one weed researcher.
Because the seeds of many plants need a brief flash of light to induce germination, planting by the light of the moon could be the secret to slowing weed germination. And that could allow crops to get a jump on weeds in the spring, which allows them to compete better against weeds later on.
Research carried out in Rosemount, Minnesota, shows it works, at least in small test plots.
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“We have seen reductions in weed emergence as great as 80 percent,” said Douglas Buhler of the United States Department of Agriculture’s agricultural research service.
“It’s kind of fun at first when you put on the night vision goggles and turn all the lights off and you’re driving around the field in the middle of the night.”
But when Buhler left the soil research plot to try the method out with a local farmer, the thrill wore a bit thin.
The dashboard lights on the farmer’s new John Deere tractor, which operate independently of the rest of the vehicle, were enough to blind someone wearing night vision goggles, which proved necessary to see the rows.
“Even when a car came down the road nearby he had to stop because there would be too much light and it just freaks out the whole system,” Buhler said.
“You also get to wondering is it really safe to be driving around the field in the dark in the middle of the night.”
The method will likely have the greatest application for small-scale organic farmers, who are willing to use almost anything to control weeds without chemicals, he said.
Researchers at USDA’s Minnesota research centre tested 14 common weed species in small plots.
Military technology
Half of the plots were tilled during the day and others at night. The night task was made easier when an unexpected partner joined the project offering night vision goggles.
“As the military in this country scaled back in the last few years, companies selling this technology were looking for new markets,” said Buhler.
“If this is something farmers might actually do, it would be a mother of a market for that technology.”
Night seeding works best on small-seeded broadleaf weeds such as pigweed, wild mustard and lamb’s quarters.
“Usually, farmers till before planting to stimulate weed growth. They later knock out those weeds that come up by tilling or with herbicide or both,” Buhler said.
Night tillage postpones or prevents some weed emergence, causing seeds left buried to become less viable and more prone to attack by soil microbes.
If fewer weeds appear, that means fewer tractor trips and reduced herbicide use, he said.
The reduction of weed emergence after tillage in the dark compared to during daylight in the Rosemount test was 60 percent for lamb’s quarters, 48 percent for common ragweed, 40 percent for pigweed species, and 35 percent for wild mustard.
“It’s not hocus pocus. There are physiological reasons why a seed would do this, but it doesn’t work on all weeds,” Buhler said.
Annual grassy weeds (barnyard grass, giant foxtail, green foxtail, yellow foxtail) and large-seeded broadleaf weeds (common cocklebur, giant ragweed, velvetleaf) had similar emergence whether tillage was done in the light or the dark.
“It’s kind of out there,” said Dave Kelner, a soil specialist with Manitoba Agriculture. “I don’t see too many producers going out at 2 a.m. to start seeding.”
However, researchers say night tillage could help manage certain types of weeds. Small-seeded broadleaf weeds are a common problem in special crops like canola, flax and peas.
