Pine bark as an alternative to coco coir for substrate production of long-cane raspberry in southeastern USA

Raspberries are a high-value crop that are not commercially grown in the hot, humid climate of the southeastern USA. Annual long-cane production involves growing plants in pots or bags filled with soilless media and placing them in tunnels when the season is more moderate in the spring. This system often relies on coco coir as the industry standard. However, coconut processing and transport have resulted in shortages and increasing cost of coconut products. Research at North Carolina (NC) State University has focused on the development and utilization of regionally sourced bark and wood products as substrate alternatives for multiple crops, including raspberry. The objective of this study was to evaluate plant performance in coco coir and a locally produced pine bark product. The study was conducted at Lewis Farms in Rocky Point, NC, USA. Long cane plants of ‘Kwanzaa’ were produced in a Canadian nursery in the summer of 2021, placed in cold storage in mid-October, and shipped to the farm in January. In January 2022, long cane plants were lined out (planted) in containers in Haygrove high tunnels. Two high tunnels had coco coir substrate, and two tunnels had aged pine bark substrate. Fertility and irrigation were managed by daily monitoring of fertigation input and output electrical conductivity (EC), as well as percent drainage. Total yield was collected on each picking date by counting the number of flats harvested per row. Fruit size was collected by weighing a 10-berry sample from each row, seven times during the harvest season. At the end of the season, plants were destructively sampled to assess the number of laterals, lateral length, lateral dry matter, total flower buds, and fruitful flower buds. Plant tissue samples were collected every 2 weeks to assess plant nutrient status. The number of fruiting laterals, total flowers, and fruitful flowers were the same for each soilless treatment. Fruiting laterals in coco coir were longer than fruiting laterals in pine bark and had greater dry matter accumulation. However, there was no significant difference in total yield or fruit size between the two substrates. Plant tissue samples showed no difference in N, P, K, S, B, or Ca between the two substrates. There were slight differences in Mg and Fe. Based on this 1-year study, pine bark appears to be a viable substrate for long-cane raspberry production in southeastern USA.