Intercropping results in high overall system productivity on a given piece of land due to the efficient use of available plant growth resources. Weed control in intercropping systems is, however, still a challenge. This study focuses on the effect of the type of weed control (chemical/mechanical) and the timing of chemical herbicide application (pre-emergence/post-emergence) on weed control and crop productivity in a maize bean mixture. For this purpose, the results of a three-year field experiment (2017 to 2019) in northeast Germany will be presented. The experimental setup included a control, three chemical methods, and one mechanical method of weed control. Except for the mechanical treatment, a completely randomized block design was established. Weeds were assessed at BBCH 12 of the maize, immediately before the first weed control treatments to estimate the initial weed infestation, and twice in the six to eight leaf stage of the maize. The weed coverage (%) was estimated. The maize bean mixture was harvested and yields (t ha⁻¹) were measured. The results confirm that the type of weed control, as well as the timing of herbicide application, significantly affects the weed coverage of the maize bean mixture. The most successful weed control strategy was the double chemical herbicide application, in which chemical herbicides are in used pre-emergence beans (BBCH 12 maize) and post-emergence beans (BBCH 12 bean). Weed coverage was reduced by up to 75% using this most effective herbicide strategy and by up to 61% through mechanical weed control, compared to the control. The additional effects of post-emergence treatment on the pre-emergence herbicide control resulted in a 16.5% weed coverage decline. The yield surplus of double chemical herbicide application (pre/post-emergence) was up to 53%, and for the mechanical weed control up to 23%. Additionally, post-emergence herbicide use in intercropped maize and bean resulted in a 16% yield surplus, compared to the single pre-emergence chemical weed control. Optimal timing of weed control during the most sensitive phenology stages of the maize bean mixture is crucial for productivity. The results of this study provide an additional option for suitable weed control of intercropped maize and bean.

Based on a workshop held at the German Weed Science Conference in February 2024, this paper explores strategies for reducing herbicide use in arable cropping systems to enhance weed diversity. Although potentially detrimental to crop yields, weeds play a vital role in supporting ecosystem functions such as pollination, nutrient cycling, and microbial diversity. The reduction of herbicide use is regarded as an important management strategy for preserving weed biodiversity, which has been declining in Europe. Three strategies for reducing herbicide use are discussed: site-specific herbicide application, species-specific herbicide dose rates, and the use of selective herbicides with narrow target spectra. Each strategy is evaluated for its technical feasibility, agronomic risks, and potential benefits for weed diversity. While challenges such as high investment costs, technical limitations, and the need for precise weed distribution data remain, emerging technologies like AI-driven weed detection and autonomous robots offer promising solutions. The paper emphasizes the importance of combining reduced herbicide use with other management practices, such as crop rotation and mechanical weeding, to achieve sustainable and ecologically beneficial weed control. A shift in farmers’ perspectives on “clean fields” and more comprehensive guidance on the ecological value of weeds is essential for the widespread adoption of these strategies.