Dissolved oxygen (DO) refers to the concentration of oxygen gas (Oβ) dissolved in the nutrient solution and available to plant roots. Roots require oxygen for aerobic respiration β the process that generates the energy needed for nutrient uptake and growth. In waterlogged or stagnant systems, dissolved oxygen depletes rapidly, forcing roots into anaerobic respiration, which produces ethanol, damages root cells, and creates conditions that favour root rot pathogens.
Key Facts
- Optimal dissolved oxygen level: 6β8 mg/L (ppm) for most hydroponic crops
- DO decreases as water temperature rises β cold water holds more oxygen
- Air stones and air pumps are the primary method for maintaining DO in reservoir systems
- Water falls, cascades, and spray nozzles also oxygenate solution through surface agitation
- Anaerobic conditions (low DO) are the primary cause of root rot (Pythium) outbreaks
- DWC systems are particularly susceptible to DO crashes if air pumps fail