Weeds problematic in second crop maize cultivation in Diyarbakır province and investigation of sustainable weed control possibilities in different tillage methods

The aim of the study is to investigate sustainable soil tillage and weed control methods in second crop corn farming. The study consisted of three stages. The first stage of the study was to determine how different tillage systems and herbicide applications affect weed density and grain yield in the second crop corn (Zea mays L.) cultivation after barley harvest. For this purpose, a two-years field experiment was carried out in the experemental areas at Agriculture Faculty, Dicle University, Diyarbakır, Turkiye in the 2022-23 growing season, comparing different soil tillage methods [conventional tillage (mouldboard plough+cultivator), reduced tillage (disc harrow) and no-tillage] and herbicide applications [pre-emergence, post-emergence, pre-emergence + post-emergence, weed-free control, weedy control]. In the experiments carried out with three replications according to the split plot design in randomized blocks, the main plots were composed of soil tillage methods and the sub-plots were composed of herbicide applications. As a result of the study, it was determined that different tillage methods had no effect on weed density and grain yield. However, herbicide applications were found to be effective on weed control and crop yield. It was concluded that the sequential applications of pre and post-emergent herbicides significantly reduced weed density and biomass weight and increased grain yield. In the second stage of the study, surveys were carried out to determine the density and frequency of weed species in second crop maize cultivated areas in Diyarbakır province and districts. A total of 367 sampling was carried out in 45 fields in 5 districts of Diyarbakır province. Weed species with a frequency above 9 % in second crop maize fields in the province were Xanthium strumarium (L.), Sorghum halepense (L.) Pers., Portulaca oleracea (L.), Triticum aestivum (L.), Convolvulus arvensis (L.), Physalis angulata (L.) Pers. and Amaranthus retroflexus (L.).I n the third stage of the study, surveys were conducted with 156 second crop maize farmers in Diyarbakır province in order to investigate the methods and equipment used in maize cultivation, the weeds encountered, the ways of controlling them and the level of knowledge on the use of herbicides. A moderate weed density was reported by the growers with Johnson grass (Sorghum halepense (L.) Pers.) and common cocklebur (Xanthium strumarium L.) being the most problematic weeds. A significant number of the producers rely on post-emergence herbicides for weed control. Additionally, 94 % of the producers are satisfied with the herbicides, and the most preferred herbicides (66.04 %) contained mesotrione + nicosulfuron active ingredients. The producers conveyed that the plow is more effective in weed control among tillage tools and emphasized that both tillage and herbicides should be combined for effective weed management. It was also observed that addressing the challenges faced during second-crop corn production in Diyarbakır through education, demonstrations, and incentives could significantly contribute to the sustainability of agricultural production and increase second-crop corn cultivation.