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In the absence of new herbicides on the market, adding adjuvants into the tank with herbicides is a strategy for increasing efficacy. In our research, we tested whether there are differences in weed control as influenced by the original nicosulfuron formulation and a generic counterpart. In this study, we tested the addition of two commonly used adjuvants: ammonium-sulfate (AMS) and non-ionic surfactant (NIS). In a three-year experiment, based on a percentage of biomass reduction and canopy cover, these results showed no differences in any treatments when comparing the original versus generic nicosulfuron. However, adding an NIS increased efficacy, while adding AMS decreased herbicide activity. The average percentage reduction of biomass in this study was about 80%, implying that using solely nicosulfuron as aceto-lactate synthase inhibiting herbicide is not a good solution in weed control in maize and that other methods for weed control should be considered and integrated, in order to increase weed control efficacy.

AbstractWeed 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% to 90% of the weed population in many spring crops, such as soybean [Glycine max(L.) Merr.], sunflower (Helianthus annuusL.), and corn, in Serbia. Currently, acetolactate synthase–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 adjuvant 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 to 2022 to evaluate the impact of two adjuvants (a non-ionic surfactant [NIS] and a mineral fertilizer ammonium sulfate [AMS]) 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 NIS adjuvant 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 Extended Range (XR) TeeJet®nozzles on average resulted in a higher efficacy for common lambsquarters compared to Turbo TeeJet®induction. Adding a mineral AMS adjuvant resulted in lower biomass reduction for both nozzle types and weed species (65% to 78% and 61% to 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.

To control weeds and cultivate maize (Zea maysL.) with higher yields, production systems have to include more efficient forms of N and appropriate herbicide treatments. The timing of N release could give maize an advantage over weeds in competition for resources, whereas cultivation at lower row spacing often decreases weed biomass. Knowledge about the different factors affecting herbicide efficiency increases the accuracy and reliability of chemical control. This study tested the weed infestation level and the development and productivity of a recently developed maize hybrid grown with the application of several integrated practices. The maize hybrid was sown with application of standard and slow‐releasing urea, with row spacing of 50 and 70 cm and treatment with either a pre‐emergence or a post‐emergence mix of herbicides. The numbers of plants of each weed species and their biomass were lower after the application of herbicides, although N form and row spacing produced no significant differences in the average weed infestation level for 3 yr. The post‐emergence herbicide treatment was more effective than the pre‐emergence treatment for weed biomass reduction and enhancing maize yield parameters. The N form did not influence any measured yield parameter, whereas the 70‐cm row spacing resulted in significantly higher harvest index and grain yield (0.45 and 9.19 Mg ha−1, respectively) than the 50‐cm spacing (0.43 and 7.36 Mg ha−1, respectively). The wider row spacing resulted in higher grain yield through its interaction with N form and herbicide treatment.