Integrated effects of crop rotation and different herbicide rates in maize (Zea mays L.) production in central Serbia

Successful maize (Zea mays L.) cultivation is largely reliable by weed interference. Among weeds, annual species are usually dominant, whereas less prevalent perennials can be challenging to control, too. Driven by profitability, maize is often cultivated continuously using the same management practices over time, resulting in increased weed infestations, particularly perennials. However, crop rotation might reduce the abundance of weed species, lower herbicide impact on the environment, delaying herbicide resistance occurrence in weeds and thus contribute to sustainable maize production,. The aim of this study was to explore the impact of continuous maize cropping (Maize-CC) and a three-crop rotation, maize–winter wheat–soybean (Maize-WW-S), in combination with three weed management treatments: 1) application of a pre-emergence herbicide mixture of acetochlor/S-metolachlor + isoxaflutole at the full label rate, 2) at ½ of full label rate, and 3) an the untreated control, over a 12-year period. The trial was initiated in 2009, and maize was grown in both cropping systems, Maize-CC and Maize-WW-S, in 2012, 2015, 2018, and in 2021. Total weed density, fresh biomass of all annual and perennial weed species and total dry biomass of all weed species was measured four weeks after herbicide application. Maize leaf area index (LAI) was measured at the anthesis, whereas grain yield was measured at the end of the growing cycle. Weed species diversity, number of individuals, weed fresh and dry biomass, were significantly lower with the combination of Maize-WW-S and the herbicide treatments. Grain yield was significantly and negatively correlated with the fresh weight of annual weeds in Maize-CC and was higher in both herbicide treatments, especially in Maize-WW-S. There was no significant difference between pre-emergence herbicide full labelled rate and ½ of the labelled rate in reducing the total fresh weed biomass in Maize-CC (66.3% and 65.9%, respectively) and Maize-WW-S (92.1% and 85.8%, respectively). Thus, the importance of the combined employment of rotation and chemical measures in maize production was confirmed and could be adopted for long-term weed management without compromising yields.