Performance of Sprayable Liquid Mulches Based on Industrial By‐Products for Weed Control in Tree Nurseries

Sustainable new solutions for controlling weeds in tree nursery production are needed. This study assessed the performance of pyrolysis liquid containing sprayable fibre sludge mulch (FLM) compared with the corresponding peat-based mulch (PLM) and non-mulched control in forest tree nursery production. Experiments were conducted with grafts of Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and European silver birch (Betula pendula). During the first growth period, the effects of mulches on the number and species of weeds and on soil temperature and moisture were assessed. Both mulches prevented weed growth equally during the first 6 weeks. Twelve weeks after mulching, the number of weeds in PLM was 1.9 and in FLM 3.3 times lower than in the non-mulched plots. Neither mulch affected the survival of the tree seedlings over the two monitored growing seasons. However, PLM increased spruce and birch growth significantly, while FLM reduced birch growth. The temperature and moisture of growing media were slightly lower in FLM treatment than in PLM or the non-mulched soil. The results indicate that liquid mulches provide a new alternative for weed control in tree nurseries. Analysing the techno-economic performance of FLM showed that it might well be economically feasible compared with manual weeding or currently available biodegradable mulches. The study highlights the potential of liquid mulches as an alternative to conventional practices, including black plastic and herbicide use, in the horticulture and agriculture sectors and supports the development of a circular bioeconomy by introducing new applications for industrial side streams and creating a more diverse toolkit for future weed management.