Plasma-Activated Water as an Alternative Nitrogen Source: Effects on Lettuce Growth and Mineral Composition

Plasma-activated water (PAW) is enriched with reactive oxygen and nitrogen species (RONS). Application of PAW in plant cultivation demonstrated that RONS promote seed germination and early plant growth, as well as stimulate plant defense mechanisms. The aim of this paper was to investigate the potential of reactive nitrogen species in PAW to partially replace urea fertilizer nitrogen in lettuce cultivation without resulting in a negative effect on growth and mineral composition. Lettuce was grown under two treatments: urea only and a combined treatment in which 10% of the urea-derived nitrogen was replaced by an equivalent amount of nitrogen supplied via plasma-activated water (PAW). Plant growth parameters of lettuce (number of leaves, head weight, rosette diameter and height, and dry matter weight) were measured. Concentrations of 21 elements in the plants were analyzed using inductively coupled plasma optical emission spectroscopy (ICP—OES). Results showed no significant difference in growth parameters between the two treatments, as well as no significant difference between treatments in the concentrations of most elements except magnesium, boron and sodium. The results demonstrate that PAW reactive nitrogen can partially substitute for nitrogen from synthetic fertilizer without negative effects on the growth and nutritional content of lettuce. The study contributes to the development of sustainable horticultural fertilization practices and the adoption of environmentally friendly technologies.