The development of microbially enhanced plant growing media

Thijs Van Gerrewey is a Ph.D. candidate in the Faculty of Bioscience Engineering at Ghent University, Belgium, under the supervision of Professors Danny Geelen (HortiCell) and Nico Boon of the Center for Microbial Ecology and Technology (CMET). Together with Urban Crop Solutions (a turnkey vertical farming system solutions provider) and Agaris (a leading European growing media supplier), they are developing microbially enhanced plant growing media to improve plant quality and health in (vertical) hydroponics. Vertical farming can improve the food safety and security of the growing urban world population under the increasing occurrence of climate change. However, vertical farms are only profitable in specific niche markets (geographical niches or added value chain models) because of the high investment and operational costs. Therefore, to make vertical farming more widely applicable, these niches need to be expanded. Many growing media materials (e.g., wood fiber, composts, coir pith) are being introduced as sustainable alternatives to peat. As the fast-expanding media market develops, different blends of materials are being used. A diverse rhizosphere is essential for plant health. Using microbial biostimulants could promote plant growth, however, growing medium composition may be a determining factor in the successful application of microbial biostimulants in (vertical) hydroponics. Our knowledge of the impact of different growing media materials on microbial functioning remains limited. Therefore, we collected five lettuce rhizosphere inocula from different farms in Belgium. We then composed ten different growing media. Lettuce was grown in each growing medium, inoculated with the bacterial community inocula, and transferred to a vertical farm. At harvest, plant growth and quality were determined, and the rhizosphere communities were identified using 16S rRNA gene sequencing. The main conclusions were: 1) inoculation effectiveness depended on the inoculum source and its interaction with the growing medium; 2) growing medium composition determined the rhizosphere community; 3) inoculation with a bacterial consortium allowed for more control over the rhizosphere compared to a single species inoculum; 4) increased plant performance was linked to higher bacterial diversity. Overall, these results show the potential of microbially enhanced plant growing media to modulate plant performance in (vertical) hydroponics.

Thijs Van Gerrewey won the ISHS Young Minds Award for the best oral presentation at the II International Symposium on Growing Media, Soilless Cultivation, and Compost Utilization in Horticulture in Belgium in August 2021.

Thijs Van Gerrewey, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium, e-mail: thijs.vangerrewey@hotmail.com

The article is available in Chronica Horticulturae