Using gorse compost as a peat-free growing substrate for organic strawberry production

ABSTRACT The demand for peat-free organic growing media has increased and green compost provide an attractive option within a circular economy. To take advantage of the inherent nutrient content, the nutrient dynamics need to be carefully considered when evaluating the agronomic potential of compost for organic production. In this study, the use of compost made from gorse (Ulex europaeus L.) was evaluated as a substrate for organic production of strawberries (Fragaria x ananassa Duch ‘Selva’), focusing particularly on the availability of nutrients. Two gorse composts were used, gorse composted with poultry manure (5% v/v) (PM100) and gorse composted on its own without manure (PM0). The composts were assessed in their original form and in formulations containing different proportions of each. A fertilised standard peat-based substrate was used as control. Both PM0 and PM100 exhibited acceptable physical properties and contained high concentrations of major nutrients (particularly PM100). The nutrient concentrations in the solutions from the different formulations decreased gradually during the growth of the crop, particularly N and K. Concentrations of N and chlorophyll levels were lower in plants grown in gorse compost formulations than in those grown in the control. There were, however, no substantial differences in fruit size or overall yield. The above-ground biomass in the compost-grown plants increased with increased proportions of PM100, but it was greater in the control plants. The gorse composts were recommended as effective peat substitutes for strawberry cultivation, although supplementary fertiliser should be applied at fruit production stage to ensure optimal production.