The Rotary Hoe
Contending with a soil crust on your emerging sunflower field? Need some extra early season control of shallow-rooted weeds? Didn’t get a preplant herbicide on that solid-seeded field? Don’t use chemicals in your farming operation?
Those are just a few of the situations where a rotary hoe can come in awfully handy for sunflower producers, says North Dakota State University extension agronomist Duane Berglund. “I think it’s one of the more under-utilized tillage tools available for our row crops,” he ventures, adding that the rotary hoe “will work just as well in sunflower as in corn and beans.”
As with so much of farming, timing is everything when employing a rotary hoe. Sunflower producers have a couple windows of hoeing opportunity, Berglund advises: (1) a “blind tillage” pass three or four days after planting, and (2) while the young ’flowers are in the two- to six-leaf stage of growth.
“With blind tillage, nothing’s emerging yet — not even weed seedlings,” the NDSU specialist notes. “But you can do a lot of damage to weed seedlings at this stage. Meanwhile, you’ve hopefully planted the sunflower deep enough (around two inches) so they’re protected.”
The next opportunity comes after the ’flowers have emerged and reached at least the true two-leaf stage, beyond the cotyledon phase. “By then the sunflower is a little more anchored, not quite as tender, more resilient,” Berglund points out.
It’s important, he adds, to conduct any postemergence rotary hoe operations on warm, sunny afternoons — and while the soil surface is quite dry. The sunflower plants will be more flaccid or flexible by midday, resulting in less crop injury. Even so, the rule of thumb is that a stand reduction of approximately five percent can be expected with each hoeing, so growers anticipating the use of a rotary hoe may want to increase their planted population accordingly, Berglund says.
One of the rotary hoe’s advantages is speed — typically between eight to 12 miles per hour. “Effectiveness is greater at faster speeds,” Berglund points out. “But injury to delicate crops also will increase with speed because there is more soil disturbance.” (Continued on Page 20)
hile it can be a very effective weed control or crust-busting tool, the rotary hoe naturally has its limitations, too. It will not, for example, give good control of large-seeded weed seedlings or of weeds germinating at deeper depths. Weeds like wild mustard, kochia, pigweed, foxtail and nightshade are easily controlled by hoeing, while wild oats, volunteer grains and cocklebur are not. Perennial weeds are not controlled — or even suppressed — by the rotary hoe.
Nor are rotary hoes as useful under high-residue field conditions. “They’re just not effective,” Berglund says. “Also, the extra trash can build up, start ‘bucking’ the soil and actually do more damage than good (i.e., reduce crop stands excessively).” The rotary hoe is best suited for situations where residue cover is less than 25 percent, according to Berglund.
Hoeing’s effectiveness also can be impaired in field with numerous small stones, as the stones can get wedged between wheel or between points on the same wheel.
Berglund knows of soybean producers who successfully use rotary hoes on solid-seeded fields, and he sees no reason why it wouldn’t work for solid-seeded sunflower as well.
“But if you’re going to have solid-seeded ’flowers, I’d advise doing the rotary hoeing as soon as possible,” he says. “Don’t wait for the four- or six-leaf stage.” Since the tractor tires would be passing over many emerging sunflower plants, compaction in wheel tracks also could be a significant concern if the topsoil was on the wet side, Berglund adds.
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