Subsurface drip irrigation and low-dose ozone application: Enhancing lettuce growth without compromising soil health

This study evaluated the effects of integrating subsurface drip irrigation (SDI) with ozone application on lettuce (Lactuca sativa L.) cultivation, focusing on plant growth, soil properties and microbial dynamics. Three field trials (F1, F2 and F3) were conducted using two lettuce varieties, assessing three irrigation treatments: T1–surface drip irrigation without ozone; T2–SDI without ozone; and T3–SDI with ozone-enriched irrigation water, in a RCB design. Ozone was injected to the irrigation system using a Venturi-based system. Results across the three field trials showed that ozone application at low doses (0.4–0.7 ppm) did not significantly affect soil oxygen diffusion rate (ODR), volumetric water content, microbial populations, or soil CO2 efflux (p > .05). ODR values remained below 50 µg cm−2 min−1 across treatments, with no detectable improvement associated with ozone. Likewise, soil respiration did not differ between ozone-treated and control plots, indicating no impact on microbial activity. Microbial analyses confirmed this pattern, with similar bacterial counts between treatments. In contrast, subsurface drip irrigation (SDI), particularly when combined with ozone (T3), consistently enhanced lettuce growth. In F1, ‘Quenty’ reached 201.82 g fresh weight in T3 compared to 101.22 g in T1, while in F2 and F3, T3 significantly outperformed other treatments (p ≤ .03). SDI also improved soil moisture stability at 10–15 cm depth, reflecting higher efficiency. Overall, these findings indicate that low-dose ozone is a safe strategy that does not compromise soil health and when combined with SDI, produced higher biomass under the same irrigation regime.