Sustainable organic growing media in a commercial tomato growing system

Almost 95% greenhouse vegetable production in VS, Canada and EU is cultivated on substrates. In Western Europe mineral substrates like rockwool and perlite are most commonly used in soilless cultivation practices, while LCA studies shows that mineral substrates scored worse compared to substrates that are easy to recycle. Research Station Hoogstraten (Belgium) tested six different sustainable organic growing media based on woodfibers (30%), coir (40%) bark (20%) and compost (10%) on the 'Rebelski' (De Ruiter) variety, grafted on the rootstock, Maxifort (De Ruiter) in a commercial tomato (Lycopersicum esculentum) greenhouse within the interreg 2seas project “Horti-BlueC”. Five substrates had an addition of respectively 2 g L^‑1 biochar; 4 g L^‑1 biochar; 2 g L^‑1 chitin + 2 g L^‑1 biochar; 2 g L^‑1 chitin; 2 vol% Hortiviv (Trichoderma spp.) to test an effect on plant resilience and plant production parameters. The tested substrates were compared with rock wool (control) and a peat (80%) substrate (control). The tomato plants were planted 12 December, 2020 at a planting distance of 50 cm with a stem density of 2.5 stems per square meter. The growing season lasted till 22 October 2020. The harvest started on 17 March, 2020. During the growing season, plant, fruit, substrate, diseases and pest and production parameters were measured. No significant differences in production (kg m^-2) were found. The plant parameters were encouraging for all objects. The brix values were not affected, but fruits were softer compared with fruits grown on the control growing media. No agrobacterium disease was observed in the experiment, thus no conclusions about the effects of the different substrates on plant resilience can be made. In general, the control substrates (rock wool and the peat substrate) were more moist than the alternative substrates. The highest EC (mS cm^‑1) was found in the rock wool slabs. It looks like the alternative sustainable growing media can be implemented in current commercial tomato cultivation.