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6. Aeration & pumps

11 years ago

    Why oxygen Plants need oxygen; without it their roots drown. Oxygen (02) dissolved in the nutrient (dissolved oxygen or DO) provides this need. (DO) helps the plant absorb nutrients & prevents algae. Commercial growers may measure DO with DO meters or home use may simply monitor for oxygen deficiency symptoms.

Symptoms of an oxygen deficiency are: Stunted growth. Wilting in the sun & heat.
Calcium deficiency: burned tips & blossoms, rotten fruit, yellow leaves; leaves & flowers drop off. Decreased root growth

Causes of 02 deficiencies are:

As roots grow 02 need increases.

Elevated nutrient temperatures in the summer. Increased heat decreases the ability of oxygen to stay in nutrient while at the same time the plants need for oxygen is increased.

Increasing system oxygenWays to increasing DO depends on the system. Passive systems provide 02 as nutrient drops into the drainage reservoir. The greater the drop height, the greater the 02 dissolved. Active systems provide 02 in various ways. The ebb and flow of the flood drain system provides 02to the roots. Aeroponic systems provide the best 02of all systems because of their air misting system. Active systems primarily provide oxygen, however, through use of air pumps & airstones.

Air pumps connect to air stones to provide oxygen. Selection depends on ones system size. Systems need to have the capacity to increase oxygen during hot weather. Air pumps may be noisy due to their vibration. To quiet them place them on a towel or hang them from a bungee cord.

Air pumps connect to air stones, which create small air bubbles & increase DO. The size of the bubble is determined by the size of the stone & its pore size. Small pore stones need a high pressure pump & block easier so medium pore stones are commonly used. Airstones have parameters on their packages to aid in selection for ones system. Airstones should be weighted down or they will vibrate. They also need to be soaked prior to using them package directions will specify this. Finally, air stones also need to be cleaned as they may clog. One way of doing this is to soak them over night in a weak hydrogen peroxide solution.

Water pumps can also play a role in increasing DO. Water pumps may be submersible or the non submersible. Since small pumps may not pump the nutrient up a significant height into an upper reservoir a larger or more powerful pump may be needed. When selecting a pump one need to know the distance their solution needs to travel up their reservoir. Pumps are rated gallons per hour (GPH) at a certain pumping height. The higher the water must travel, the more powerful the pump is needed. Because of power outages, backup battery air and water pumps (or some alternative system) are advised. Timers can be used to manage pumps & are of varying degrees of sophistication.

Other ways to increase DO are:

The more time the bubble is in water the greater the DO. A deep air tank & airstones at the bottom increases the distance the bubble travels.
Breaking the water flow into a fine shower creates more air bubbles & thus more DO. Some growers use a waterfall pump in addition to their water pump to do this. Add a small amount of hydrogen peroxide to the solution.
Faster flow rates, greater slopes in systems. A venturi, an air tube added to the pump tube, uses pump pressure to pull in air & increase DO.
Commercial growers use ozone generators to increase DO. Ozone is oxygen with an extra oxygen molecule attached. When ozone comes in contact with water vapor hydrogen peroxide is produced. High ozone levels can be dangerous, however, & ozone gives off a foul chemical smell well before reaching high levels. Users need to be aware of the safety issues for the device they are using.

© 2004 Baci


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