Effects of nozzle type and adjuvant selection on common lambsquarters (Chenopodium album) and johnsongrass (Sorghum halepense) control using nicosulfuron in corn

Weed control in corn is a major challenge due to increasing problems with highly dominant weed species and herbicide resistance evolution. Common lambsquarters and johnsongrass constitute up to 80-90% of the weed population in many spring crops such as soybeans, sunflower or corn in Serbia. Currently, acetolactate synthase (ALS)-inhibiting herbicides such as the systemic selective sulfonylurea nicosulfuron are most commonly used for chemical weed control of those species. A better understanding of the impact of nozzle type and adjuvants use on nicosulfuron efficacy can help to improve control of common lambsquarters and johnsongrass and minimize herbicide resistance development. Field trials were conducted in Serbia from 2020-2022 to evaluate the impact of two adjuvants (a non-ionic surfactant and a mineral fertilizer ammonium-sulphate) and two nozzle types (drift-reducing nozzles and flat-fan nozzles) on common lambsquarters and johnsongrass control using nicosulfuron. Satisfactory biomass reduction of common lambsquarters (83 to 87%) and johnsongrass (83 to 97%) was achieved after nicosulfuron application. Adding a non-ionic surfactant increased the biomass reduction for common lambsquarters (94 to 98%) and johnsongrass (90 to 100%) independently of the nozzle type used. Selection of nozzle type did not show consistent effects on common lambsquarters and johnsongrass control. Nicosulfuron efficacy was increased with NIS adjuvant for both nozzle types compared to nicosulfuron solo for both species, and XR nozzles on average resulted in a higher efficacy for common lambsquarters compared to TTI. Adding the mineral fertilizer ammonium-sulphate adjuvant resulted in lower biomass reduction for both nozzle types and weed species (65-78% and 61-91% for common lambsquarters and johnsongrass, respectively). Corn grain yield was predominantly influenced by annual meteorological conditions and adjuvant type added to nicosulfuron. This research suggests that addition of the non-ionic adjuvant is an essential factor for successful control of common lambsquarters and johnsongrass in corn and enables use of drift-reducing nozzles.