Agrochemicals in field margins—Field evaluation of plant reproduction effects

Field margins are important habitats for various plant species in agro-ecosystems but they can also be exposed to agrochemicals. In this experimental field study, effects of herbicide, insecticide, and fertilizer misplacements in field margins on the plant frequency and reproductive capacity of four wild plant species (Ranunculus acris, Lathyrus pratensis, Vicia sepium, Rumex acetosa) were investigated from 2010 to 2012. Individual and combined effects of the agrochemicals were studied in a randomized block design and plant community assessments were performed every year. Additionally, seeds of the four species were harvested in 2012 to detect effects on plant reproduction. Plant frequencies of the four species were significantly reduced in all herbicide and fertilizer treatments in the third year. The plant frequency of R. acris and L. pratensis was more affected in the fertilizer treatments than in the herbicide treatments, whereas the plant frequency of V. sepium and R. acetosa was similarly affected by fertilizer and herbicide treatments. However, the treatment combinations of fertilizer and herbicide resulted in additive effects on the plant frequency of V. sepium and R. acetosa. Furthermore, herbicide treatments suppressed the formation of flowers and, hence, led to a significantly reduced seed production of R. acris, L. pratensis, and V. sepium. Because field margins are exposed to repeated agrochemical applications over several years, the observed effects will possibly lead to shifts in plant community compositions and cause the disappearance of the affected plants in the long run. In the current risk assessment of herbicides for nontarget plants no reproduction effects are considered, and therefore, it seems that herbicide effects on wild plants species are potentially underestimated.