Air CO2 versus root oxygen
Scale
Enriched air at 1,500 ppm is 0.15% CO2. Oxygen is still about 21% of air
Leaf job
Leaves take CO2 through stomata. Roots do not photosynthesize and have no use for CO2
No room conflict
Raising room CO2 to garden levels has little effect on oxygen the water can hold
Surface exchange
At the air-water film, water gives off CO2 and takes up O2. Circulation makes that swap faster, even in an enriched room
Optional O2 tank
Extra oxygen in water or soil can still help roots grow faster and take up feed more efficiently
When CO2 hurts roots
Competition
CO2 and O2 both dissolve and compete in water
Seltzer in the pot
Watering with carbonated water eventually degasses in the medium and pushes oxygen out of pore space
Result
Roots starve for oxygen, respiration drops, and uptake fails
Same as a fish tank
Still water keeps waste CO2 and loses oxygen. Movement fixes both
What oxygen-starved roots do
Uptake stall
Roots cannot pull water and nutrients well, then stop growing
Pathogens
Weak roots invite disease. Anaerobic bacteria thrive and can make ammonia. An ammonia smell means no oxygen
Media
Do not pack soil tight. Pores must hold air as well as water
Hydro
Circulate and aerate to strip CO2 and reload oxygen
Temperature
Warm water holds much less oxygen than cool water
Ways to add oxygen
Waterfall
The drop from a table into a reservoir is a natural enricher
Bubbler or pump
An aquarium stone or submersible pump keeps new water at the surface
Hydrogen peroxide
1 part 3% H2O2 to 10 parts water. Extra oxygen is gone in 72 hours or less
Stronger H2O2
Higher rates kill fungi and bacteria, including helpful soil life. Use that strength only when you are fighting pathogens
Payoff cited
Oxygen-rich conditions gave about 50-60% more growth on cuttings and about 30% on rooted plants in the experiments the book cites
Low O2
Water that is poor in dissolved oxygen slows growth