Effects of organic and chemical nitrogen fertilization and postharvest treatments on the visual and nutritional quality of fresh‐cut celery (Apium graveolens L.) during storage

The shelf life of horticultural commodities depends on pre‐ and postharvest factors, such as soil fertilization and postharvest handling. The current study aimed to evaluate fresh‐cut celery's postharvest quality as affected by the rate and type (organic and chemical) of nitrogen (N) fertilizer and postharvest treatments. Celery (‘Tall Utah’) crop was grown in a field in Karaj, Iran. The experimental design was a randomized complete block with three replications and seven preharvest (fertilizer), and five postharvest treatments. Organic fertilizers were vermicompost (VER) and bio‐organic fertilizer [farmyard and livestock manure plus Trichoderma harzianum (COM)]. Chemical fertilizers were urea (46% N) at high rate [322 kg·ha(1) N (UREA_HIGH)], optimal rate [196 kg·ha(−1) N (UREA_OPT)], and low rate [138 kg·ha(−1) N (UREA_LOW)]; ammonium nitrate [35% N (AN)] at 196 kg·ha(−1) N; and treatment without fertilization was used as a control. Postharvest treatments included plastic packaging (PP), hydrocooling (HC), blanching (B), and edible coating of psyllium seed mucilage (EC). After postharvest treatments, celery petioles were stored (0–2°C, 85%–90% RH) for 4 weeks and evaluated weekly for quality attributes. Organic fertilizers and UREA_LOW were the most effective treatments in reducing the changes in color, weight loss, titratable acidity (TA), pH, and total soluble solids (TSS) of fresh‐cut celery. Organic fertilizers enhanced the vitamin C content, total phenols, and antioxidant activity in celeries. As postharvest treatments, hydrocooling, plastic packaging, and blanching maintained chroma and hue values. Blanching had the greatest effect on the L* value. Hydrocooling increased celery's TA, TSS, and vitamin C content and reduced weight loss and pH during storage. Thus, celery quality was improved when grown under low or adequate N fertilization. Hydrocooling was an effective postharvest treatment for preserving fresh‐cut celery quality during storage.