Polyethylene and biodegradable plastic mulches improve growth, yield and weed management in floricane red raspberry

Polyethylene (PE) mulch and biodegradable plastic mulches (BDMs) have been used in annual vegetable and strawberry (Fragaria x ananassa Duch.) production systems for several decades due to their ability to suppress weeds, modify soil temperature and moisture, and promote earlier and greater yields. However, there are only a few studies that have explored mulch use in perennial production systems. The overall objective of this study was to compare PE mulch and BDMs to growers' standard practice of bare ground (BG) cultivation in a floricane red raspberry (Rubus idaeus L.) production system in northwestern Washington, USA. Cumulative weed growth, root lesion nematode [Pratylenchus penetrans (Cobb) Filipjev and Schuurmans Stekhoven; RLN] population densities, soil temperature and moisture, cumulative plant growth, and fruit yield were evaluated in a 'Wake-Field' red raspberry field in 2017 and 2018. Compared to the BG control, PE mulch and BDMs suppressed weeds and generally increased soil temperature. Root lesion nematode population densities were greater in soil covered with PE mulch than Novamont 0.5, and were greater in raspberry roots from plots treated with PE mulch than BASF 0.6 and the BG control. Primocane height and number were higher for plants grown with mulches relative to the BG control in 2017. Average fruit yield of plants from the mulched treatments was 34% greater than the BG control. Overall, this research demonstrated that PE mulch and BDMs improved raspberry plant growth and yield. These findings demonstrate the potential benefits of using PE mulch and BDMs for improving establishment in perennial crops.