Organic producers are interested in testing propane flaming as part of an integrated weed management program for organic crop production. Field experiments were conducted at the Haskell Agricultural Laboratory of the University of Nebraska, Concord, NE in 2007–2008 and 2008–2009 utilizing several doses of propane applied at different plant growth stages depending on the crop and the weed species evaluated. The response of plant species to propane doses was described by log-logistic models based on visual estimates of injury and plant dry weight. Grass weed species were more tolerant than broadleaf species. A propane dose of about 76 to 85 kg/ha provided a 90% dry matter reduction at 14 days after treatment in grasses compared to 40 to 68 kg/ha broadleaf species.

Corn treated at 5-L was the most tolerant stage for broadcast flaming, whereas 2-L stage was the most susceptible, resulting in the highest visual crop injury, dry matter reduction, and yield loss. Soybean at cotyledon (VC) stage was the most tolerant whereas unifoliate (VU) stage was the most susceptible to broadcast flaming resulting in the highest visual crop injury, and the largest yield loss.

Additionally, greenhouse experiments were conducted at University of Nebraska-Lincoln East Campus Lincoln, NE during April and September of 2009. Two crops (corn and soybean) and two weed species (velvetleaf and green foxtail) were evaluated. Leaf relative water content (RWC) was measured before treatment application. All plant species had lower leaf RWC during the afternoon. This low RWC increased their susceptibility to flaming.

Based on these results, plant response to flaming was influenced by propane dose, growth stage, and time of day when flaming was conducted. Broadleaf weeds and soybean were more susceptible, while grass weeds and corn were more tolerant to broadcast flaming. Plants flamed during the afternoon presented more damage than the ones flamed in the morning. Flaming has a potential to be used effectively in controlling weeds in organic crop production systems when conducted properly at the right crop and weed growth stages and at the appropriate time of day.