Journal of Crop Production and Processing

Extended Abstract
Introduction: Weed competition remains one of the most significant constraints to achieving optimal corn (Zea mays L.) yields, particularly during the critical early growth stages when the crop exhibits limited competitive ability against invasive weed species. In Iran’s major corn-producing regions, annual broadleaf weeds such as Amaranthus retroflexus, Chenopodium album, and Xanthium strumarium have emerged as particularly problematic, capable of causing yield losses exceeding 40% under severe infestation. Chemical control remains the most efficient and economically viable weed management strategy; however, the heavy reliance on a limited range of herbicides most notably the environmentally concerning atrazine has led to multiple challenges, including the development of herbicide resistance and increased risks of environmental contamination. Therefore, the registration and evaluation of new herbicide formulations with different modes of action have become essential for establishing sustainable weed management systems that maintain high productivity while addressing these emerging threats. This study systematically evaluates the efficacy of several promising herbicide options, including thifensulfuron-methyl, terbuthylazine, bromoxynil + MCPA, and bentazon + MCPA, across three distinct agroecological zones in Iran. Particular emphasis is placed on assessing weed control spectrum, the effects of application timing, yield enhancement potential, and phytotoxicity risks. By developing science-based recommendations for herbicide selection and application protocols tailored to regional weed pressures, this research aims to contribute to more resilient and sustainable corn production systems in Iran and comparable agricultural environments facing similar weed management challenges.

Materials and methods: The experiment was conducted using a randomized complete block design (RCBD) with 12 treatments and four replications during the 2022–2023 growing season. Herbicide treatments included thifensulfuron-methyl (20–36 g a.i./ha, pre-emergence), bentazon + MCPA (2 L/ha, post-emergence), terbuthylazine (1.8 L/ha, pre- and post-emergence), bromoxynil + MCPA (1.5 L/ha, post-emergence), as well as weed-free and untreated control plots. Measured parameters included weed density, dry weight reduction, visual injury (EWRC scale), and corn grain yield. Data were analyzed using SAS 9.1, and treatment means were compared using Duncan’s multiple range test at α = 0.05.



Received: May. 30, 2025; Revised: Dec. 12, 2025; Accepted: Dec. 15, 2025; Published Online: Apr. 08, 2026.
* Corresponding Author: nezamabadi_n@yahoo.com
Results and Discussion: Bromoxynil + MCPA (1.5 L/ha) achieved the highest weed control in Kermanshah, with 96% density reduction and 98% dry weight reduction, followed by terbuthylazine (1.8 L/ha, pre-emergence) and thifensulfuron-methyl (36 g/ha). Xanthium strumarium and Physalis divaricata were effectively controlled (>90%) by bromoxynil + MCPA. In Alborz, bromoxynil + MCPA and 2,4-D + MCPA provided complete weed control, whereas lower doses of thifensulfuron-methyl (20–28 g/ha) were less effective. In Ardabil, thifensulfuron-methyl (32–36 g/ha) and pre-emergence terbuthylazine reduced weed density by 85–91%, with Abutilon theophrasti controlled at approximately 75%. Yield increases ranged from 13% to 40% across treatments, with bromoxynil + MCPA and terbuthylazine performing comparably in weed suppression and yield enhancement. These results provide compelling evidence that strategic herbicide application can substantially improve weed management and yield potential in corn production systems. Overall, bromoxynil + MCPA (post-emergence) and terbuthylazine (pre-emergence) emerged as the most effective treatments, providing over 85% control of economically important broadleaf weeds, including A. retroflexus, C. album, and X. strumarium, across diverse agroecological zones. Although thifensulfuron-methyl demonstrated promising activity, its optimal performance required precise dosage calibration (32–36 g/ha), underscoring the importance of accurate application in modern weed management practices.

Conclusions: The consistent 13–40% yield enhancement across all effective treatments compared with untreated controls highlights the substantial return on investment achievable through proper herbicide use. Minimal phytotoxicity observed across treatments confirms the crop safety of these herbicides when applied in accordance with recommended guidelines. Regional variations in herbicide performance emphasize the necessity of adapting weed management strategies to local weed spectra and environmental conditions to maximize efficacy. These findings have significant implications for the sustainable intensification of corn production in Iran and similar agroecosystems. By offering effective alternatives to older herbicides such as atrazine, the results contribute to resistance management and environmental safety. Future research should focus on (1) developing integrated weed management systems combining chemical and cultural practices, (2) exploring tank-mix strategies for broader weed control, and (3) conducting long-term studies on herbicide resistance dynamics. Implementing these science-based recommendations will enhance both the economic viability and environmental sustainability of corn production under increasing weed pressure and regulatory constraints.