Rotary hoeing

To control weeds, approximately 90% of U.S. agricultural acreage is treated with nonchemical, mechanical weed controls, such as mechanical cultivation and rotary hoes (15), whereas only about 25% receives treatment with herbicides (13). 

Crop Chain harrow Harrow comb Culti- vator Finger weeder Brush hoe Rotary hoe Flame weeder... 

Research by an Iowa State University botanist concluded that on the nonchemical farm, weed populations in the plots hoed four times were similar to those in herbicide-treated fields on other farms (Jurik, 1993). He also estimated that seed production from redroot pigweed that emerged on the farm was between 40 million and 400 million total seeds per acre (100 million to 1000 million seeds per ha). In an effort to improve the efficacy of the rotary hoe operations, experiments have been conducted using double rotary hoe passes on fields on the same day (Thompson and Thompson, 1994). 

A publication from the Land Stewardship Project describes four sustainable farms in Minnesota (Chan-Muehlbauer et al, 1994). None of the four farmers use herbicides in their corn fields. For weed control they rely on extended crop rotations with alfalfa, mechanical cultivation with a rotary hoe and cultivator, and late planting of com to allow mechanical control of the first flush of weeds. One farmer reported that the com crop is cultivated three to five times. The report details the 1992 com yields at these four farms in comparison to the average yields in the same regions. In all cases, the yields of the sustainable farms were lower than the average yields in their regions. The reduced yields for the four farms were -38%, -11%, -7%, and -5%. 

A 1991 New Farm article profiled two Ohio corn farmers who used a rotary hoe for weed control (Culp, 1991). One farmer intended to continue with the rotary hoe. He estimated that it works ideally 2 years out of 10, gets shut out by weather about as often, and is usable to some degree in the other 6 years. If wet weather prevents timely use of the rotary hoe, this farmer uses a rescue treatment of herbicides. The other farmer was selling his rotary hoe because late-season weeds in the com row depressed corn yields by 30% in the rotary-hoed fields, compared to fields where herbicides were used. In addition, this farmer estimated that cultivations cost significantly more per acre than herbicides 25/A ( 62/ha) for three rotary hoeings and two cultivations, versus 13 to 16/A ( 32 to 40/ha) for herbicides. 

Rotary hoes or harrows are the first tillage operation used on organic farms. 

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