Allelopathic potential of Lingonberry (Vaccinium vitis-idaea L.) litter for weed control

The total phenol contents of air-dried/composted lingonberry (Vaccinium vitis-idaea L.) shoots and air-dried lingonberry roots were determined, and the phenolic composition was analysed using reverse phase high-performance liquid chromatography (HPLC). In addition to the simple phenol derivatives (arbutin and hydroquinone) the shoot material contained polyphenols (catechins and flavonol glycosides) and phenolic acids. The effects of lingonberry shoot powder (0.5-3 g petri dish(-1)) on seed germination of garden cress (Lepidium sativum L.) were investigated in laboratory bioassays. In additional experiments, the effects of pure arbutin and benzoic acid on seed germination (0.1-10 mM) and on early seedling growth (0.001-0.5 mM) were studied. Air-dried lingonberry shoot powder (2-3 g) strongly inhibited seed germination and was lethal, whereas composted shoot powder had no effect. Benzoic acid inhibited seed germination more than arbutin, but both decreased the root elongation at concentrations > 0.1 mM. During the early seedling growth stage, benzoic acid increased seedling mortality at 0.01 mM concentration. These results indicate that air-dried lingonberry shoot powder has a pronounced allelopathic effect on garden cress at several growth stages. The effects apparently derive from the abundance of phenolic constituents in shoot powder. Bioassay results suggest that phenolic acids also have marked allelopathic effects. The importance of the allelopathy of lingonberry litter for the weed control of field cultivated lingonberry is discussed.