Flame weeding: Effects of burner angle on weed control and temperature patterns

Abstract

The effects of flame burner angle on control of small weeds were studied in the field. An open burner was directed at five angles towards the ground: 45 and 67° aimed forwards and backwards, and 90° straight down. A burner angle of 67° directed backwards gave the highest weed reduction, but there were no significant differences between the effects of the different burner angles. Weed species with protected growing points were tolerant to flames, whereas species with sensitive leaves and exposed growing points were susceptible. Temperatures in the flame were measured 1 cm above the ground in a rail track in the laboratory with the same burner angles and speed that were used in the field. The temperature‐time curves were analysed for maximum temperatures as well as the period of time and temperature sum above certain temperatures. There were significant differences in temperature between different burner angles but no significant relationships between the different thermal parameters obtained in the laboratory and the weed control in the field. It is concluded that evaluating thermal weeders based solely on indiscriminate temperature measurements is unreliable.