Plants grown in a hydroponic system need dissolved oxygen (DO) in their water to thrive and provide optimal yields; in hydroponic systems, most oxygen absorbed by plant roots comes from the nutrient solution you provide.
Going beneath the surface: The root system, or “rhizosphere”
Plants receive nutrition via two different conduits: The aerial environment, in which photosynthesis and respiration occur, and the rhizosphere, the “below the surface” environment. It’s just as important to pay attention to what happens below the surface as it is to what happens above. If you don’t give plant roots the oxygen they need, your plants – and harvests – could suffer.
Root oxygen starvation
Without adequate oxygen, roots become less permeable and can no longer absorb nutrients or water effectively. If left as is, plants begin to starve. This can mean stunted growth and even plant death.
You control how much DO the roots get
In your grow room’s hydroponic system, you’ll be controlling how much oxygen your plant roots get. They need from 7 to 10 PPM. (The water you use should be as pure as possible before your nutrient addition; the purer the water, the more DO it can hold.)
Methods of DO production and effective aeration/nutrient delivery
Plant roots like to be covered with a fine “blanket” of tiny oxygen bubbles in a hydroponic system, for best absorption of DO and nutrients. However, not all methods are created equal: Be careful what you use.
- Hydrogen peroxide
I list this first because this is one of the most commonly used methods of DO production but it is NOT suitable for your plants’ DO needs. Here’s why: Hydrogen peroxide (H2O2) has an extra oxygen atom vs. water (H2O). H2O2 converts to water (H2O) plus an oxygen atom with a negative charge (O2-). That O2– atom is a free radical that will indiscriminately damage healthy plant tissue. Stay away from hydrogen peroxide, and instead opt for the method below.
DO use both:
- An air pump in combination with an air stone
Air will diffuse into water as soon as it comes into contact with it, and many growers use the combination of an air stone and air pump to add DO to their nutrient/water mixture. It’s an inexpensive way to increase DO levels. The air pump pumps air through food-grade plastic tubing that is attached to an air stone at the bottom of the receptacle. The stone “breaks up” the air into tiny bubbles, and they increase the DO levels of the water as they rise to the surface. (This method also keeps nutrients and water well mixed.)
- A stirring pump
While the air pump/air stone combination for DO production creates exactly what plant roots need, it will also react with the CO2-enriched air of the grow room and cause the pH of the fertilizer/water mixture to rise over time. Stirring the water continuously or at regular, timed intervals keeps the water’s DO concentration stable. Stirring also prevents stagnation and will help prevent harmful bacterial growth.