Fertilization of radishes, tomatoes, and marigolds using a large-volume atmospheric glow discharge

Abstract

A large-volume atmospheric glow discharge has been used to incorporate nitrogen species into aqueous solution that is subsequently used to fertilize radishes, marigolds, and tomatoes. Treatment with plasma activated water (PAW) was compared to a tap water control. Water application began immediately after seeding and continued for 4 weeks. At the conclusion of the experiment, PAW treated plants had shoot masses 1.7-2.2 times larger than controls. Subsequent research has focused on optimizing the amount of nitrogen in solution by varying discharge power, air flow, air-water interface, and water alkalinity. When the discharge hovers over a stationary water phase, nitrate concentrations increase with decreasing power and increasing air flow. When water droplets are injected directly into the plasma, nitrate concentrations increase with increasing power and decreasing air flow. These contrasting trends are believed to depend on the balance between hydroxyl and electron concentrations in the discharge. Adding NaHCO3to water before plasma treatment affects both the amount of nitrogen present in solution as well as the ratio between oxidized and reduced species. Concentrated NaHCO3solution had 2.9 times more total nitrogen, 59 times more nitrite, and 27 % less nitrate after plasma treatment than a solution with no NaHCO3. Two factors could contribute to the spike in nitrite and decrease in nitrate: reaction of nitric and nitrous oxides with bicarbonate to form nitrite, and a decrease in disproportionation of nitrate that occurs readily at acidic pH but negligibly under neutral conditions.