ASHS 2025 Conference

Plasma-activated water (PAW) is a novel irrigation medium enriched with reactive oxygen and nitrogen species (RONS) which significantly modify the physiochemical properties of water, yet their inherent instability is influenced by processing parameters such as plasma exposure time and storage conditions. Although studies have demonstrated PAW’s promising effects on seed germination and plant growth, knowledge regarding its application to enhance microgreen production is limited. Therefore, the objective of this study was to elucidate the effects of PAW processing time and storage duration on the PAW chemical properties and on the yield and quality of pea (Pisum sativum L.) microgreens. Tap water was treated using a gliding arc plasma generator (200 mA, 2.6–2.7 kV) provided by Plasma Licensing Authority Inc. (New York, NY) for 30, 60, 90, and 120 minutes. Controls included untreated tap water and tap water supplemented with 100 ppm NH₄NO₃. PAW properties- pH, EC, NO₃-N, NO₂-N, and H₂O₂- were analyzed immediately after treatment and at 5, 24, 48, 72, and 96-hours post-treatment. PAW was applied to pea microgreens in two experimental sets: (1) within 12-hour post-generation and (2) after 72-hour of storage at ambient temperature. PAW initially exhibited lowered pH in all treatments; but after 96 hours in the first experiment, pH of the 30-minute treatment increased to 7.68±0.01 compared to tap water (7.62±0.01), while in the second experiment, all treatments remained lower. NO3-N increased with processing time and storage duration compared to tap water. Fresh weight of microgreens receiving immediately generated PAW exceeded that of tap water (979.48±26.88 g/m²) except for the 120-minute treatment (864.48±66.08 g/m²). After 72 hours of storage, all PAW treatments improved fresh weight compared to tap water, with 60-min and 90-min treatments exceeding NH₄NO₃ by 4.06% and 6.11%, respectively. Shoot length decreased slightly with 120-min PAW (-1.06%) compared to tap water in the first experiment but increased across all treatments in the second. Storing 120-min PAW for 72 hours raised total N pea shoot content (7.66±0.079%) compared to tap water (7.48±0.136%), while Ca levels increased in all PAW treatments relative to tap water and NH₄NO₃. These findings suggest that PAW processing and storage time influence reactive species and nitrogen levels, impacting microgreen yield and quality. Overall, these results highlight the potential dual function of PAW in the sustainable production of microgreens: i) as sanitizer and/or as eustressor immediately post-generation and ii) as a synthetic nitrogen fertilizer replacement after storage.