Drip irrigation with nanobubble oxygenated treated wastewater improves soil aeration

Long-term drip irrigation with treated wastewater (TWW) is known to enhance oxygen deficiency (hypoxia), especially in fine-textured soils. Hypoxia conditions around plant roots negatively affect growth and yield. Experiments were conducted to evaluate the response of lettuce grown in well-aerated (sandy) and poorly aerated (clayey) soils to surface and subsurface drip irrigation with nanobubbles oxygenated TWW (ONB-TWW). Oxygen mass balances show that irrigation with ONB-TWW supplied about 1% of the daily O[sbnd]CO₂ emissions. Nevertheless, our results show that both surface and subsurface drip irrigation with ONB-TWW increased the lettuce yield regardless of the soil type or the amount of oxygen added to the soil out of the daily oxygen consumption in it. Irrigation with ONB-TWW significantly reduced membrane leakage and osmotic potential in the roots and leaves in both well-aerated and poorly aerated soils, concomitantly improving root viability and chlorophyll content in the leaves of the plants grown in the poorly aerated clayey soil. The results suggest that drip irrigation with ONB-TWW, should be considered as a viable method to improve oxygen availability in soils and to alleviate soil hypoxia. Further study is needed to elucidate the mechanisms by which ONB promote plant health and growth.