Optimizing Residual Herbicides in Mid-south Cropping Systems

Download or read book Optimizing Residual Herbicides in Mid-south Cropping Systems written by Benjamin P. Sperry and published by . This book was released on 2019 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adoption of conservation tillage and the use of cover crops for benefits associated with soil health and weed control has increased in recent years. In these systems, the reliance on postemergent (POST) herbicides such as glyphosate has resulted in widespread resistance in weeds. Consequently, residual herbicides must also be used in conjunction with conservation tillage practices and POST herbicides to reduce risk of further resistance evolution. However, residual herbicide applications to crop residue covered soil commonly results in herbicide losses of up to 50% due to interception and adsorption to organic matter (OM). Therefore, greenhouse and field experiments were conducted in 2017 and 2018 in effort to identify application methods and other practices that result in greater efficacy when residual herbicides are applied to crop residue. In the field, efficacy of residual herbicides after application to crop residue-covered soils was enhanced with increasing carrier volumes and most herbicides performed better with XR nozzles compared to TTI nozzles. However, minimum carrier volumes and nozzles required for successful weed control were largely product-specific. In a greenhouse experiment, the addition of a silicone-based adjuvant at an optimal concentration improved acetochlor efficacy after application to wheat straw. Likewise, acetochlor efficacy from application to wheat straw was increased with greater volumes of simulated rainfall. In addition to conservation tillage related experiments, field experiments were conducted in 2017 and 2018 in Mississippi and Nebraska to quantify the relative duration of weed control provided by many commonly used residual herbicides in effort to identify when weed control starts to decline relative to initial application. Lastly, a field experiment was conducted investigating the effects of carrier volume and spray quality in simulated dicamba drift on susceptible soybean experiments. Carrier volume was found to profoundly affect soybean response to dicamba and should be considered in future simulated drift studies.