Analytical Investigation of Plasma Physics Parameters in Atmospheric Pressure Dielectric Barrier Discharges for Agricultural Seed Treatment in Nigeria

Non-thermal plasma treatment at atmospheric pressure using dielectric barrier discharges has emerged as a promising seed priming technology that enhances germination rates and early seedling vigor without chemical inputs. This study analytically investigates the plasma physics parameters of a dielectric barrier discharge reactor designed for seed treatment applications, with experimental validation using commonly grown Nigerian crop seeds from Kaduna State, North West Nigeria. Plasma diagnostic measurements including optical emission spectroscopy, electrical characterization using Lissajous figures, and gas temperature measurement by rotational spectrum analysis of the second positive nitrogen emission system were performed to characterize the reactive species content and plasma power density as functions of applied voltage, frequency, and gas composition. Treatments using air and argon carrier gases were compared. Statistical design of experiments using a Box-Behnken design was applied to evaluate the interaction effects of discharge power density, treatment duration, and electrode gap on seed germination percentage, germination index, and seedling root elongation for soybean, sorghum, and cowpea seeds. Results indicate that optimized air plasma treatment at 3 W/cm2 for 90 seconds increased soybean germination percentage by 18 percent and seedling root length by 32 percent relative to untreated controls. Nitric oxide and ozone emission intensities, both documented seed priming mediators, showed strong positive correlation with germination enhancement. The study provides mechanistic analysis linking plasma chemical physics to agronomic seed treatment outcomes relevant to Nigerian smallholder farming systems. Keywords: atmospheric pressure plasma, dielectric barrier discharge, seed treatment, plasma diagnostics, Nigeria agriculture