Postharvest Quality and Safety of Potted Greenhouse Tomato Grown on Forest Soil-Biosolids substrate, Blended with NPK Fertilizer

Abstract

Studies on the effects of biosolids (BS) amended substrate on food quality and safety in tomato production have not been adequately addressed. The objective of this study was to investigate the influence composted BS and NPK fertilizer in forest soil on post-harvest quality and safety of potted greenhouse tomatoes. Potted tomatoes ‘Maxim F1’were grown in a randomized complete block design with four replications. Inorganic fertilizer NPK fertilizer was applied at 0, 100 and 200 kg ha-1; BS was applied at 0%, 10%, 20%, 30%, and 40% v/v, in all possible combinations. Tomato were harvested and analyzed for ascorbic acid, chlorophylls, carotenoids and total phenolic compounds; weight loss, fruit firmness, titratable acidity and total soluble solids, as well as heavy metals and microbial contaminants. Results revealed that tomato fruit at 10% BS in combination with NPK fertilizer at 100 kg ha-1had highest β-carotene (6.1 mg 100 g-1), lycopene (26.1 mg 100 g-1), ascorbic acids (128.0 mg 100 g-1), total phenolic acids (13.2 mg 100 g-1), total soluble solids (17%). However, the same rates produced tomato fruits with lower titratable acidity (2.2%) and had heavy metal residues within the permissible level, according to International EPA standards on biosolids utilization on food crops production. Similarly, no trace of targeted bacteria; Salmonella, Escherichia coli, Staphylococcus was observed on the ready to eat tomato. This study reveals BS 10% with NPK fertilizer at 100 kg ha-1 substrate as a better option of plant nutrient source for quality and safe greenhouse tomato production.