Effects of olive solid waste and olive solid waste compost application on soil properties and growth of Solanum lycopersicum

•Olive oil production is a major industry that produces large volumes of toxic waste.•Direct application of olive waste is harmful to vegetation and soil health.•Most notably olive waste inhibited root growth and morphology.•Composting of olive waste enhanced soil properties and photosynthetic performance of tomato.•However, excess application of this olive waste compost negatively affects plant production.

Mediterranean countries are the largest global producers of olive oil. One by-product of this industry, and a major environmental problem, is olive solid waste (OSW). This study aims to explore the potential of OSW and olive solid waste compost (OSWC) for reuse and recycling as an agricultural fertiliser. Typical Sandy and Loamy agricultural soils were augmented with increasing amounts of OSW and OSWC (0, 4, 8 and 10%) in order to investigate the effect on soil characteristics and growth of tomato (Solanum lycopersicum). Plant growth was dramatically reduced by the application of OSW Composting of OSW results in a break-down of toxic compounds. Consequently, augmentation of soils with OSWC enhanced seed-germination, plant and root biomass and total nitrogen content. Application of 4–8% OSWC produced the optimal effect on soil parameters across all treatments, while plant growth subsequently decreased when OSWC application was increased to 10%. These results suggest that composting of OSW has the greatest potential beneficial impacts for the use of this agri-industrial waste as an agricultural fertiliser. To ensure optimal impact on crop production application of OSWC should be within 100–210 tonnes per hectare, and not exceed 260 tonnes, significantly greater than current standard compost application rates.