Narrow-windrow burning to control seeds of Italian ryegrass (Lolium perenne ssp. multiflorum) in wheat and Palmer amaranth (Amaranthus palmeri) in soybean

Abstract

Narrow-windrow burning (NWB) is a form of harvest weed seed control in which crop residues and weed seeds collected by the combine are concentrated into windrows and subsequently burned. The objectives of this study were to determine how NWB will 1) affect seed survival of Italian ryegrass in wheat and Palmer amaranth in soybean and 2) determine if there is a relationship between NWB heat index (HI; the sum of temperatures above ambient) or effective burn time (EBT; the cumulative number of seconds temperatures exceed 200 C) and the post-NWB seed survival of both species. Average soybean and wheat windrow HI totaled 140,725 ± 14,370 and 66,196 ± 6224 C, and 259 ± 27 and 116 ± 12 seconds of EBT, respectively. Pre-versus post-NWB germinability testing revealed there was an estimated seed kill rate of 79.7 % in Italian ryegrass, and 86.3 % in Palmer amaranth. Non-linear two parameter exponential regressions between seed kill and HI or EBT indicated NWB at a HI of 146,000 C and 277 seconds of EBT potentially kills 99% of Palmer amaranth seed. 76% of soybean windrow burning events resulted in estimated Palmer amaranth seed kill rates greater than 85%. Predicted Italian ryegrass seed kill was greater than 97% in all but two wheat NWB events, therefore relationships were not calculated. These results validate the effectiveness of NWB’s ability to reduce seed survival, improving weed management and combating herbicide resistance.