Hydromulch Suppresses Dicot but Not Monocot Weeds and Maintains Yield and Fruit Quality in Established Blueberry

Woven plastic mulch (“weedmat”) is widely used in northern highbush blueberry ( Vaccinium corymbosum ) production due to its capacity to suppress weeds, improve soil microclimates, and increase yields. However, weedmat and other mulches made with nonbiodegradable plastics are difficult to recycle, resulting in large amounts of plastic waste being landfilled. Complete removal of plastic mulch from fields is challenging, resulting in macro- and microplastic contamination of agricultural soils and the surrounding agroecosystem. Although soil-biodegradable plastic mulches address many of these issues in conventional agriculture, no commercially available product meets the criteria of the US Department of Agriculture National Organic Program. Hydromulch is a closed-loop, sprayable, biodegradable mulch technology that could provide a sustainable alternative for organic growers while preserving the horticultural benefits of plastic mulch. However, research on hydromulch efficacy in perennial systems is scarce. The objective of this experiment was to ascertain the effects of multiple hydromulch formulations on weed and whip suppression, yield, fruit quality, tissue nutrient status, and seasonal durability [measured as percent soil exposure (PSE)] in an established planting of ‘Valor ® ’ northern highbush blueberry cultivated in a dry climate. Two hydromulches formulated using a singular cellulosic feedstock with or without a 4% guar gum were compared with a weedmat control in 2023 and 2024 in a dry climate. Hydromulch formulations had a significantly greater number and biomass of monocot weeds when compared with weedmat due to higher levels of seasonal mulch deterioration. Yield and fruit quality in hydromulch treatments were similar to the weedmat, although the 4% guar gum treatment had a slightly lower yield relative to the no tackifier hydromulch treatment in 2023. Statistically significant but inconsequential deviations from leaf tissue nutrient standards for Eastern Washington were observed but were not attributed to hydromulch treatment. This study illustrated that the evaluated hydromulch formulations suppressed dicot but not monocot weeds while maintaining yield and fruit quality in an established blueberry field. Future hydromulch research should focus on increasing its physical and mechanical properties to enhance monocot weed suppression, the cost-benefits of hydromulch adoption, and understanding any soil health implications of hydromulch use.