If your weed control arsenal doesn't include a newer-model rotary hoe, you may be missing a good bet.
"A rotary hoe is one of the most effective and cost-effective weed management strategies you can use," declares Iowa State University weed specialist Mike Owen. "And if you're in reduced or conservation tillage, the newer models handle residue better than the old ones."
Duane Berglund, North Dakota State University agronomist, agrees. The implement can also be an effective tillage tool for breaking a soil crust to aid crop emergence, he adds.
Rotary hoeing can appropriately be called "blind tillage" because you often can't see the weeds or effect you're having on them, points out Berglund. Many growers are reticent about utilizing the rotary hoe because they fear crop damage.
"Most crops planted 1-2" deep escape appreciable injury from the rotary hoe," Berglund assures. "For best results, weed seedlings should be in the white sprout stage between germination and emergence.
"Once weeds have emerged and turned green," the scientist reminds, "you're two steps behind in effective use of the rotary hoe."
Rotary hoe three to five days after planting under most conditions, Berglund advises. Doing it again five to seven days later provides improved weed control.
But crop safety is a consideration, he admits. For each hoeing after the crop is emerged, expect a 5-7% stand loss. That can be offset by increased planting rates. And little if any stand loss will occur if the crop is just starting to germinate. Take extra care not to cover the crop as it emerges, he notes.
Hoeing requires a dry, firm soil surface and several rain-free hours afterward so weed seedlings can die. Hot, windy conditions after hoeing are best.
Rotary hoeing during midday and afternoons is often quite effective.
The hoe does have some weed control limitations, notes Berglund. It won't satisfactorily control large-seeded weed seedlings or weeds that germinate deeper in the soil. Weeds like wild oats, cocklebur and sunflower all germinate deeper - too firmly anchored for rotary-hoe control.
Shallow-germinating small-seeded annual weeds such as wild mustard, kochia, pigweed, foxtail and nightshade are easily controlled by hoeing. But perennial weeds aren't controlled or even suppressed.
What about hoeing speed? Berglund recommends operating speeds of 7-14 miles per hour.
"Effectiveness is greater at faster speeds, but injury to delicate crops will increase with speed because there is more soil disturbance."
Corn can be hoed practically anytime after planting until the crop is 4-5" tall, he says. One exception: from when the spike is within 1/2" of the soil surface until the one-leaf stage if the soil is loose. Avoid hoeing then to prevent excessive covering.
Soybeans should not be hoed from the crook stage, just before emergence, until approximately five to seven days after emergence, when beans are in the one- to two-trifoliate leaf stage.