Extending the lifetime of coconut coir media in strawberry production through reuse and amendment with biochar

Coconut coir is a medium that has been used extensively in soilless tabletop strawberry production in the UK for over a decade, particularly as a more sustainable alternative to peat-based media. A more sustainable and economically attractive option for growers is to extend the number of seasons that the coir medium could be used. However, experiments by the UK industry have reported reductions in strawberry yield with reused coir. The current study aimed to gather more information regarding this reported yield decline. In addition, fruit quality (Brix) was also assessed. In 2018 and 2019, the June-bearer strawberry cultivar 'Malling Centenary' was used, and in 2020 the ever-bearer strawberry cultivar 'Prize' used. In 2018, unused and once-used coir were tested. In 2019, unused, once-used and twice-used coir were tested. In 2020, unused, once-used, twice-used, and three times used coir were tested. The effect of adding woody biochar (oak, beech) on fruit yield and quality were also investigated. Regarding 'total class 1 yield per plant' or 'yield', there was no significant effect regarding coir age or biochar amendment. The highest 2018 yield over 4 harvests was for the once used coir beech biochar amended (170 g), while the lowest was once used coir oak biochar amended (139 g). Regarding 2019 yield, there was no significant effect regarding coir age or biochar amendment. Regarding berry quality (Brix) in 2019 over two selected harvest dates, there was no significant effect of coir age or biochar amendment. The mean Brix in 2019 ranged from 8.24 for the twice used coir no biochar to 8.99 for the unused coir amended with beech biochar. Regarding the Brix assessment in 2020 over 6 selected harvest dates, there was no significant effect of coir age or biochar amendment. In 2020, the mean Brix ranged from 8.59 for the unused coir beech biochar amended to 9.53 for the three times used coir amended with oak biochar. The reuse of coir in strawberry production has immense potential for environmental and economic benefits in a circular economy approach. However, other factors also need to be considered such as pest and disease persistence in the coir, changes to the physical and chemical properties of the coir over time.