Flaming as a vegetation control method based on utilizing heat to increase temperatures high enough to boil water inside the plant tissue, which is then resulting in plant death from the loss of membrane and cuticle breakdown (plant desiccation), denaturation of proteins, and water boiling. Machines are available to deliver the heat utilized during the flame weeding, and they are commonly referred as “weed flamers”. A propane-fueled weed flamers utilize a propane-fueled burners to expose plant tissues to rapid heat. Several flame weeding systems are commercially available, ranging from small, handheld flamers that can be used to control weeds in residential home gardens to multi-row (tractor-pulled) flamers for use over larger acres of land. Flame weeding has a potential to be used effectively in at least 6 agronomic crops (field corn, sweet corn, popcorn, sorghum, soybean, sunflower) when conducted properly at the most tolerant growth stage.
The interest for organic crop production in the United States is increasing due to
strong demand for organic food from consumers and an attractive income potential
for organic farmers. Organic crops can be used for human consumption (food grade
crops) or making organic feed rations and different food products. Weeds are one of
the major pests and are responsible for significant reductions in crop yields. Organic
production systems do lack an effective weed management practice, as weeds are a
major production-related problem because the use of synthetic herbicides is not
allowed. Therefore, organic producers rely extensively on mechanical cultivation
and hand weeding. Mechanical cultivation is one of the most commonly utilized
weed control practices in row crops. Cultivation, however, leaves a strip of
uncontrolled weeds within 10-15 cm on either side of the crop row, directly
influencing crop yield. Also, repeated cultivation causes loss of soil organic matter,
destroys soil aggregate, increases the chance for soil erosion and promotes
emergence of new weed flushes. The labor required for hand weeding is expensive in
USA (ranging from $300 to $800 ha–1), time consuming and difficult to organize
Propane flaming (or flame weeding), is a process of exposing plant tissues to
flames coming from a propane burner, which can generate combustion temperatures
of up to 1,900 oC. Direct heat injury results in denaturation of membrane proteins,
which further results in loss of cell function
Propane-fueled flaming equipment must have several major components to carry out
a successful and safe flaming treatment. The following are basic equipment
components: propane supply tank, supply network and plumbing, torches (burner)
Ascard (1995) classified weed species to four groups according to their susceptibility to propane flaming. The first group consisted of species with unprotected growing points and thin leaves [e.g., common lambsquarters (Chenopodium album L.)]: these species can be easily controlled using propane doses of 20 to 50 kg/ha. The second group consisted of species with relatively protected growing points and leaves that were moderately heat-tolerant [e.g., common knotgrass (Polygonum aviculare)]: these species can be completely controlled, but required propane doses higher than 50 kg/ha. The third group contained species with more protected growing points [e.g., shepherd's purse (Capsella bursa-pastoris)]: these species can be completely controlled at early stages (up to 4-leaf stage), but complete control is difficult to achieve at later growth stages. The fourth group consisted of plants with creeping growth habit and well protected growing points (e.g., perennial broadleaf and grasses): these plants regrow from their below ground meristems. To control species belonging from the third and the fourth group, flaming treatments should be conducted more than once.
Knezevic et al.,
Crop susceptibility to propane flaming varies with species and growth stages
From an economic stand point, the costs of a single flaming operation applied broadcast below crop canopy could be $30–$40/ha, without taking into account the costs of the equipment and labor [current price of propane ($0.5/kg × 60–80 kg). Banded application (over the crop row) of flaming can cost $12–$20/ha due to lower propane use rates (30–40 kg/ha).
Flame weeding is an acceptable weed control option in organic production and has received renewed interest for conventional cropping systems. It can be used as part of an integrated pest management program not only for weeds but also for insect control in agronomic crops. Flaming has a potential to be used effectively in organic crop production systems of three corn types, sorghum, soybean and sunflower when conducted properly at the most tolerant growth stage. It is important to emphasise that propane flaming should not be the only method for non-chemical weed control; however, it could be part of an IWM program. Other measures are still needed to control weeds that emerge later during the growing season. More research is needed to perhaps develop new flaming equipment and methods of flaming. Information from such research would expand flaming options as part of an IWM program for both organic and conventional crop production systems.
From 2006-2012 we have conducted a series of over 40 studies, which were funded by PERC and other sources (e.g. USDA). This extensive work resulted in over 20 journal and proceeding articles about crop tolerance to heat and weed control with flame weeding in field corn, popcorn, sweet corn, sunflower, soybean, sorghum and winter wheat. We compiled the above research information into a training manual that describes the proper use of propane fueled flaming as a weed control tool in six agronomic crops (field corn, popcorn, sweet corn, soybean, sorghum, and sunflower). The flame weeding manual contains 32 pages of text and color pictures. The pictures provide visuals of crop growth stages when flaming can be conducted safely without having side-effects on crop yield. Pictures of weeds provide visuals of appropriate growth stages when weeds need to be flamed to achieve good weed control. There are six chapters in the manual: (1) The need for alternative weed control methods; (2) Propane fueled-flame weeding; (3) How flame weeding works; (4) Equipment and configurations; (5) Propane dosage at different weed growth stages, and (6) Crop Tolerance to post-emergent flame weeding. We believe that our manual provides a recipe on how to use flaming procedures and it is written in a user friendly manner that can be understood by the general public. The manual is free, it can be downloaded in a pdf format from the following website: http://www.agpropane.com/ContentPageWithLeftNav.aspx?id=1916