Late-stage potassium reduction combined with controlled atmosphere preserves postharvest quality of chicory and mizuna baby-leaf

Mineral nutrition management in soilless cultivation systems is a promising strategy for producing ‘tailored’ vegetables with specific nutritional profiles. This study investigated the effect of reducing potassium (K) in the nutrient solution and controlled atmosphere during the postharvest storage on the quality and shelf-life of chicory ( Cichorium intybus L.) and mizuna ( Brassica rapa L. var. nipposinica) baby-leaf. Three K-treatments were compared: a control (K200: 200 mg/L K), a constant reduction (K50: 50 mg/L K), and a late-stage reduction (K50-7d: K200 replaced with K50 seven days before harvest). The results showed that K reduction did not significantly affect crop yield in either species. The K50 treatment achieved the greatest K reduction in plant tissue (up to 65 % in mizuna), but also led to a decrease in dry matter and total phenols. Conversely, the K50-7d strategy reduced the K content by 19 % in chicory (from 556 to 447 mg/100 g fresh weight -FW) and by 32 % in miuzna (from 727 to 496 mg/100 g FW), while better preserving the dry matter content with a value comparable to the control (K200). During the postharvest phase, storage in controlled atmosphere (CA, 10.0/20.0 kPa O2/CO2 in nitrogen) showed better performance than air storage in preserving visual quality for 7 days. Specifically, the K50-7d treatment showed better cell membrane integrity, as evidenced by lower electrolyte leakage, and delayed senescence, with lower ammonia accumulation and higher colour retention. In conclusion, combining the K50-7d strategy with CA storage provides an effective agronomic solution for producing low-K baby-leaf vegetables for patients with chronic kidney disease, while maintaining high quality and commercial standards.