Effects of Tomato Pomace Composts on Yield and Quality of Processing Tomato (Lycopersicon esculentum Mill.) Ioannis ROUSSIS, Ioanna KAKABOUKI, Antigolena FOLINA, Aristidis KONSTANTAS, Ilias TRAVLOS, Dimitrios BILALIS* Agricultural University of Athens, School of Plant Sciences, Department of Crop Science, Laboratory of Agronomy, 75 Iera Odos Str., 118 55 Athens, Greece. * corresponding author: bilalisdimitrios@gmail.com BulletinUASVM Horticulture 76(2) / 2019 Print ISSN 1843-5254, Electronic ISSN 1843-5394 DOI:10.15835/buasvmcn-hort: 2019.0019 Abstract Organic farming encourages the use of organic waste materials as substitutes for chemical fertilizers. Tomato pomace presents an alternative to inorganic fertilizer. A field experiment was carried out to evaluate the influence of tomato pomace composts and nitrogen fertilization on agronomic and quality parameters of the processing tomato. The experiment was laid out in a randomized complete block design with three replications and five fertilization treatments (untreated, nitrogen fertilizer, tomato pomace with biocyclic humus soil, tomato pomace with manure and tomato pomace with plant residues). The results showed that the highest average fruit weight and fruit yield (163.4 t/ha) were found in plots subjected to nitrogen fertilization, while the highest total soluble solids content (4.29 °Brix), and L* and a* colour parameters, important quality parameters to processing tomato industry, were obtained through the application of tomato pomace mixed with biocyclic humus soil making organic tomatoes suitable for processing tomato industry. Keywords: Heinz 3402 F 1 , surface colour, tomato pomace compost, total soluble solids Introduction The management of processing waste constitutes a significant issue facing the food industry. Within the European Union, the food sector produces approximately 250 million tons of by-products and waste per year, of which 10% remain after the fruit and vegetable processing (Fava et al., 2015). Moreover, 30-50% of those by- products and waste come from fruit and vegetable juice production (Kasapidou et al., 2014). The global food production and thereby the amount of food waste is expected to rise, requiring an increased attention. Currently, the application of waste streams partially includes the use as feed for livestock, plant fertilizer, composting, biogas material, or as a source of pectic polysaccharides or general dietary fiber, however; a large part of them are still incinerated or landfilled. As a result, they do not produce value for farmers, but result in a loss of billions of euros in waste management and cause environmental pollution (Mirabella et al., 2014). Tomato (Lycopersicon esculentum Mill.) is one of the most widely cultivated crops with a world production of over 182 million tons in 2017 (FAOSTAT, 2019). Significant amounts of tomato are processed yearly to produce tomato juice, paste, purée, ketchup, sauce, and salsa, resulting in the generation of large quantities of a by-product, known as tomato pomace (Del Valle et al., 2006). Tomato pomace represents, at most, 5-10% of the fruit weight and is composed of around 33%