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New research puts weeds under fire

Weeds are a real pain. For organic farmers, weeds are the biggest obstacle in a quest for high yields and profitability. Because organic growers can’t use herbicides, cultivation and hand weeding are their most widely used options.

In the past four years, new research in weed flaming, using a concentrated flame to damage or kills weeds, particularly in organic row crops, has revealed that it can work effectively, without severe economic damage to the crops.

This research, funded in part by the Propane Education and Research Council, or PERC, has proven that weed flaming is truly an emerging technology that organic and conventional producers might consider.

Key Points

Flaming weeds is an emerging technology that may work for many.

Broadleaf weeds are more susceptible to flaming than grasses.

Corn and sorghum are more tolerant of flaming than other crops.


Flaming is not a new idea. According to one report, cotton and corn farmers in the South came up with the concept using kerosene burners in the late 1930s, before effective commercial herbicides were available. It was tested on sugarcane, cotton, corn and soybeans by Louisiana State University researchers in the 1940s.

New research reveals some of the same benefits early researchers observed. Flaming doesn’t damage the soil or cause erosion, and it can be applied even under wet field conditions. It is faster than tillage, and it doesn’t rob the soil of valuable moisture. It also may be less expensive, or at least less time-consuming, than hand weeding or other weed control products available to modern organic producers.

Weeds cannot escape the flame, so they can’t become resistant to it. Conventional farmers fighting herbicide-resistant weeds that have become increasingly adaptive to current herbicides might someday employ flaming as part of their weed control program.

Early test results have shown that broadleaf weeds are more susceptible to flaming than grasses. With that in mind, flaming seems to do less damage and exhibits the most potential in grass crops like corn and sorghum, compared to soybeans and sunflowers, which are less tolerant of flaming damage.

According to PERC, most farmers will use 5 to 15 gallons of propane per acre, depending on their desired control level and the crops they are growing. In field experiments conducted in 2007 and 2008 with flaming treatments applied by a four-row experimental flamer mounted on an ATV, open flames angled at 30 degrees to the soil and located about 7 inches above the surface were used to apply varied rates and pressure of propane at a speed of 4 miles per hour.

Ninety percent weed control could be gained on broadleaf weeds at rates of 11 to 15 gallons per acre. On grass weeds, rates above 19 gallons per acre were necessary. On corn and sorghum at very early growth stages, 11 gallons per acre caused about 20% crop damage. On soybeans, alfalfa, red clover and sunflowers, 20% damage occurred at the 7-gallons-per-acre rate.

Learn more online

Research continues to learn about effective flaming equipment and further crop response to varied rates and pressure. If you’d like to learn more, visit www.agpropane.com/propane-on-the-farm/agricultural-and-production-applications/weed-control.

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FLAMER SETUP: This toolbar part is set up to kill weeds with a propane flame.

This article published in the November, 2011 edition of DAKOTA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.