Intra and interspecies competition of blackgrass and wheat in context of herbicidal resistance and environmental conditions of Poland

Abstract

Blackgrass (Alopecurus myosuroides Huds.), one of the most aggressive grass-weeds in Europe, is also a strong competitor of crops. This study aimed to assess the impact of environmental conditions on the competition between 1) herbicide-resistant (BR) and susceptible (BS) blackgrass biotypes 2) the BR and winter wheat cv. Arkadia (W), and 3) the BS and W. In the replacement series model, the experiment was conducted in seven sites across Poland during two seasons (2018/19 and 2019/20). The competitive ratio (CR) was calculated for the relative biomass of plants and grain number. If CR < 1, the blackgrass is more competitive toward winter wheat, if CR > 1, the wheat is more competitive toward blackgrass. In the BR-BS experiment, the BS biotype was more competitive toward the BR one. We also found that the competitiveness between BR and BS was related to sand content in the soil. The combined interactions between W and BR or BS were also related to environmental conditions, i.e., soil texture and hydrothermal coefficient, as explained by PCA and k-means cluster analysis. In most sites, W was more competitive toward both BS and BR. Except was for two cases, located on heavy, clay soils, during humid seasons, where B was more competitive toward W. We summarize that blackgrass competitiveness towards other biotypes and wheat depends on environmental conditions; however, the phenomenon should be explored in more detail.