Weed suppression by mulches in Mentha x piperita L.

The suitability of mulch for weed control in cultivated Mentha x piperita L. has been insufficiently studied. The results of this study show that this crop is sensitive to weed infestation. The objective was to evaluate the effects of mulch materials on weed suppression and yield of M. piperita. Two organic mulches, sawdust of acacia and dry pine needles, and two synthetic mulches, silver-brown and black "agrotextile" film, were compared with hand-weeded and non-weeded controls. Weed density and biomass per species were reduced in all treatments. The best biomass reduction was achieved with silver-brown film (96.3-100%) followed by black "agrotextile" film (74.6-95.9%). The treatments also reduced total dry weed biomass; the synthetic ones reduced biomass in the range of 84.6-100%, and the organic ones 28.5-81.4%. Under synthetic mulches, M. piperita generally achieved higher yields than under organic mulches. The best yields were obtained in 2016 with black "agrotextile" film (4.2 t ha(-1)) and in 2017 with silver-brown film (1.5 t ha(-1)). Significant differences in the relative chlorophyll content of M. piperita leaves were observed between treatments. The lowest inhibition of relative chlorophyll content compared to the hand-weeded control was observed in synthetic mulches. They ranged from - 1.93-4.53%, confirming their superiority in terms of the herbal drug M. piperita. The outcomes of this study show that the application of synthetic mulches, especially the silver-brown film, seems to be the most suitable model for non-chemical weed control in M. piperita cultivation.