Organic Weed Management in Field Crops with a Propane Flamer and Rotary Hoe

Abstract

The weed management needs of organic producers are unique because they rely primarily on cultural and physical management strategies. Recommendations regarding commonly used tools for weed management could benefit this sector of agriculture. The objectives of this research were to (1) determine the optimum time of day for propane flaming to achieve maximum weed reductions while minimizing corn damage; (2) assess whether flaming, rotary hoeing, or a combination of the two tools best manages early-season weeds without injuring dry beans; and (3) evaluate the use of growing degree days (GDD) to optimize rotary hoe timing. Experiments were carried out between 2006 and 2009 in Hickory Corners and East Lansing, MI. Flaming reduced broadleaf weed densities by at least 82% when done in the morning to midafternoon but only reduced densities by 58% when weeds were flamed in the evening. Common lambsquarters, redroot pigweed, and velvetleaf were easier to control by flaming than common ragweed and common purslane. Flaming did not reduce grass weed densities. When comparing flaming and rotary hoeing, the two treatments that achieved the highest level of weed control and highest dry bean yields were flaming prior to bean emergence followed by two rotary hoeings and rotary hoeing three times (no flaming). However, the added cost of the flamer may only be justified when wet conditions make rotary hoeing ineffective. Flaming dry beans POST resulted in significant injury and yield reductions of 60%; therefore this practice is not recommended. Timing rotary hoe passes every 300 GDD (base 3.3 C) from the time of soybean or dry bean planting resulted in fewer passes compared with the 7-d or 150 GDD treatments, while maintaining similar levels of weed control and yields similar to the weed-free treatment in 1 of 2 yr for each crop.