NEWS for North Dakotans
Agriculture Communication, North Dakota
State University
7 Morrill Hall, Fargo, ND 58105-5665
June 4, 1998
The rotary hoe is an effective tillage tool for controlling weeds in growing crops and breaking a soil crust to aid crop emergence. The key to hoeing success is understanding the many factors involved.
Proper timing and operation ensure that a rotary hoe can provide economical weed control with minimum crop damage because most crops planted 1 to 2 inches deep escape appreciable injury from rotary hoeing. But to enjoy the benefits of a rotary hoe, producers need to use it properly, says Duane R. Berglund, extension agronomist at North Dakota State University.
For best results, weed seedlings should be in the white sprout stage, between germination and emergence. For producers who use no herbicides, timeliness of rotary hoeing is especially important.
"Rotary hoeing can appropriately be called `blind tillage' because you don't see the weeds or the effect you are having on their control," says Berglund. "Once the weeds have emerged and turned green, you are two steps behind in the effective use of the rotary hoe."
Rotary hoeing three to five days after planting, followed by a second hoeing five to seven days after the first, provides improved control. Hoeing requires a dry, firm soil surface with little trash and several rain-free hours after hoeing so weed seedlings can die. Hot, windy, sunny conditions after hoeing are best, Berglund says.
Rotary hoeing during mid-day or afternoons is quite effective. A rainy period several days after hoeing results in reduced effectiveness for weed control. A rotary hoe will not satisfactorily control large seedlings or those weeds that germinate at deeper depths. These weeds include wild oats, volunteer grains, cocklebur and sunflower.
Small-seeded weeds such as wild mustard, kochia, pigweed, foxtail and nightshade, which are shallow germinating, are easily controlled by hoeing. Perennial weeds are not controlled or even suppressed by the rotary hoe, Berglund notes.
"It's suggested that field operating speeds of 7 to 14 miles per hour be used for rotary hoeing," says Berglund. "Effectiveness is greater at faster speeds. However, injury to delicate crops will increase with speed, as there is more soil disturbance."
Crop safety is a consideration in timing a rotary hoe operation. Usually a 5- to 7-percent stand loss will occur with each hoeing operation once the crop has emerged. Little, if any, stand loss occurs if the crop is just starting to germinate and the hoeing is a blind-tillage operation.
"Take extra caution not to cover the crop as it emerges," Berglund advises. "Corn can be hoed practically any time after planting, until the crop is 4 to 5 inches tall. The exception is if the spike is within one-half inch or less from the soil surface and if the soil is loose. In that case, wait until the one-leaf stage to prevent excessive covering."
Soybeans and dry edible beans should not be hoed between the crook stage, just prior to emergence and for about five to seven days after emergence, or until beans are in the 1- to 2-trifoliate leaf stage. For sunflower, avoid hoeing until seedlings are in the 2-leaf stage. Sunflower can be hoed from the 2- to 6-leaf stage with little or no injury. Again, stand losses of 5 percent to 7 percent are common with each hoeing operation.
"Producers should increase their planting rates if they plan to use rotary hoeing as part of their weed management," Berglund stresses.
For additional information, request publication W-1134, titled "Mechanical Weed Control with a Harrow or Rotary Hoe," from your local office of the NDSU Extension Service.
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Source: Duane Berglund (701) 231-8135
Editor: Dean Hulse (701) 231-6136