Growth Stage Influenced Sorghum Response to Broadcast Flaming: Effects on Yield and Its Components

Abstract

There is an increasing interest among organic producers to grow grain sorghum [Sorghum bicolor (L.) Moench] under organic crop production systems and propane flaming could be part of an integrated weed management program. Therefore, the objective of this study was to investigate the response of sorghum to broadcast flaming as influenced by propane dose and crop growth stage. Field experiments were conducted at the Haskell Agricultural Laboratory of the University of Nebraska, Concord, NE in 2008 and 2009 using five propane doses applied at three growth stages that included 3‐leaf (V3), 5‐leaf (V5), and 7‐leaf (V7). The propane doses evaluated were 0, 13, 24, 44, and 85 kg ha−1 and were applied using a custom‐built (ATV mounted) research flamer driven at a constant speed of 6.4 km h−1 Crop response to propane doses was described by using log‐logistic models on the basis of visual estimates of crop injury, various yield components (plants m−2, heads plant−1, kernels head−1, and 1000‐kernel weight), and grain yield. Sorghum response to flaming varied among crop growth stages and propane doses. Based on the evaluated parameters, sorghum flamed at V5 and V7stages showed higher tolerance compared to V3 stage. The maximum yield reductions with the highest propane dose of 85 kg ha−1 were 11, 6, and 9% for V3, V5, and V7 stages, respectively. In addition, propane doses that resulted in a 5% yield loss were 13, 72, and 46 kg ha−1 for V3, V5, and V7 stages, respectively, indicating that plants flamed at V5 or V7 stage can tolerate higher dose of propane for the same yield reduction compared to V3 stage. Flaming has a potential to be used effectively in organic sorghum production if properly used.