Aeroponics Misting Frequency for Root Growth

True aeroponics use a mist of nutrients over the plant roots inside a dark growing chamber. The nutrient and spray interval will produce fast growth rates, high yields and healthy roots, as long as the root chamber is kept at temperatures between 62F to 71F with good stability.

Some of the more complicated aeroponics systems are temperature controlled. The temperature is continually monitored in the root zone of the plant. When the temperature exceeds preset thresholds, the controller triggers the misters to activate to bring the temperature down.
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When moisture is lacking in the root zone of an aeroponics system, plants can begin to senesce (premature ageing, which can result in leaf loss) and transpire less water.  Proper misting on the right schedule will prevent drying of the roots.

Simple regular interval misting method

One way to deliver nutrient spray to the roots of an aeroponic system is to use a regular, interval misting cycle. A set time is used to spray the roots for fixed durations. Some mist for three to five seconds every 5 minutes. However, this cycle can change depending on the growth stage. This technique which could change or never change during the life of the crop insures the plant roots  do not dry out. The emphasis is a regular cycle of nutrient to deliver fresh aerated food to the root, with keep in temperatures down.

So why mist only for a few seconds? Is not more better? No! The absolute perfect misting cycle will first keep the root hairs close to 100% relative humidity without much excess nutrient dripping from roots.

You only want damp roots, not dripping after a feeding. The science behind high pressure aeroponics (HPA) is to barely moisten the roots then repeat before they get too dry. This maximizes nutrient uptake.

Keep it short and sweet

Short feed or mist cycles, less than five seconds, help to prevent the ability of the 50 micron atomized droplets to recombine on the root hairs. The longer the  spray interval is per a feeding cycle the more time the droplets have to recombine into larger droplets, which defeats the purpose of a high pressure aeroponics system.

What you would like to achieve is to mist the roots just before the previous misting cycle has dried. This will encourage the fastest absorption of nutrients through the root cell walls. And guess what, this is where the low pressure systems fail terribly.

Good misting conditions

With the proper nutrient temperature and oxygen levels in the root chamber, the plant root system will NOT become water logged or root rot diseased.

The root system using a continual misting will NOT produce healthy root hairs and high yields of plant material. Continuous misting eliminates the problems of root drying out between root cycles and is one way of ensuring temperatures in the root system are stable.

However, continuous misting can introduce some problems if the system is not properly designed. Some of these are heating, lack of oxygen, clog misters and more nutrient expense.

Remember that continuous misting or low pressure areoponics is just a glorified deep water culture system and does not work the same or provide the same results as a high pressure system on an interval timer for feeding.

Vary the misting intervals

A good Aeroponic timer give the ability to control the duration of the misting time (how long the misters are on) down to seconds and control the frequency of the misters (how long the misters are off).

By changing the cycle misting timer during the plant growing stages of life, you’ll receive better production without any other improvement in the system. This is based on applying more oxygen to the root zone than continuous misting can achieve. Less is actually more beneficial than more when it comes to misting your roots.

Follow these points when using this method of misting:

1. Remember, there is not just one set point for the misting interval. The duration of the nutrient mist needed is largely dependent on the plant, the stage of the plant growth and more importantly the temperature of the root zone.
2. Different growing environments require different misting cycles. You need to experiment or depend on others with the same system and crop to achieve extreme growth. When adjusting the misting times, do it slowly and gradually over a few days, never in one big step that could shock the plant. Maybe set the misting for three seconds ON and three minutes OFF. Observe the plant’s reactions, take copious notes and log any changes, whether good or bad. Increase the misting OFF period, see what happens. Decrease the misting ON period and see what happens. Do this weekly. Watch for signs of root wilting or color change. Try and repeat this program weekly.  Most plants start with a heavy misting cycle during its initial grow and less toward the flowering or fruit stage. You could end up with one second of misting and five minutes of no misting.
3. Another benefit of an adjustable misting program is the ability to grow plants in all stages of its life. When propagating in an aeroponic system, newly clipped clones need to be constantly mist until roots develop.In the flowering stage, plants need oxygen intake to the root system to maintain its healthy appearance.
4. Besure to keep a close eye on the root development in the aeroponic chamber. Even a slight drying of the root system will result in tissue damage and may lead to pathogen diseases.
5. You must use a quality sediment free nutrient in the system for both day and night time feeding. This is important to prevent spray misters from clogging. Remember in aeroponics, the PPM (EC or concentration) in the nutrient solution needs to be less than any other soil-less systems. The root intakes the nutrient much easier and faster in an aeroponic system.

Other factors controlling nutrient uptake of roots

Most plants take up nutrients both day and night.

Temperature changes control nutrient absorption by influencing transpiration. As long the humidity is moderate, higher temperatures will increase transpiration, and the plant will demand more misting nutrient.

The ideal root zone calls for it to be slightly cooler than the plant zone during the day. Warmer temperatures in the root zone not only encourages diseases but will shut down photosynthesis and transpiration and reduce the nutrient used by the plant. The plant is shutting down.

Calcium is taken up during the nights while root pressure permits more water uptake. This allows for calcium to be carried into the plant tissue.

Aeroponic root development

Plant roots in a high pressure aeroponic system will commonly be thin and branched. Due to the mist droplet size, aeroponic roots are fine and fluffy root hairs with a light color appearance. So monitor your roots for very fluffy, fine, bright white root hairs to signal good health and development.