In conventional gardening, it is a common concern to not overwater or drown plants with too much water. How come that in hydroponics, an entirely water-based growing technique, the concern is not as common?
Properly done hydroponic systems do not drown or overwater plants because the root system is never completely submerged in water. In addition, hydroponic systems often employ air pumps and air stones to oxygenate the water, providing oxygen to the submerged root system that otherwise will drown.
A basic understanding of root systems will improve your results in hydroponics and conventional soil-based gardening. Different hydroponic techniques also water their plants differently so some are more prone to overwatering than others.
Table of Contents
- 1 Plant Anatomy
- 2 Why Do Plants Die Without Oxygen
- 3 How Come Plants Don’t Drown in Hydroponics
- 4 Can Hydroponic Plants Be Overwatered or Drown?
- 5 What Happens When Plants Are Overwatered in Hydroponics
- 6 How Can Overwatering Occur in Hydroponics
- 7 How Hydroponic Techniques Water Plants
- 8 Using Technology to Prevent Overwatering
- 9 Takeaways
- 10 Sources
Contrary to popular belief that plants only need CO2 and sunlight, plants also require oxygen to survive. Like many living organisms, plants absorb oxygen through their stomata and roots for the process of aerobic respiration – the metabolic reaction and processes which convert chemical energy to adenosine triphosphate (ATP) plant growth.
Aerobic respiration in plants is roughly the same as in other organisms but in plants the chemical energy is the product of photosynthesis. Plant respiration occurs during night because the day is reserved for photosynthesis.
A plant is a unique organism in that it can produce energy through photosynthesis and consume the same energy through aerobic or anaerobic respiration.
Under normal conditions, plants only go through photosynthesis and aerobic respiration for the production of energy and consumption of the same for growth.
When there is little to no oxygen, anaerobic respiration occurs which is an extremely less efficient method of producing adenosine triphosphate (ATP) and produces ethanol, a toxic product which kills plant cells.
This is why aeration of the roots is important to both soil and hydroponic cultivation. Instances of anaerobic respiration rarely occur in plants and never for a long period.
Plants do not drown in hydroponics because, if done right, the roots are only partially submerged in water. Some roots are in the growing medium in the grow tray or allowed to dangle in the empty space between the grow tray and the surface of the water for the sole purpose of taking in oxygen
In conjunction, airstones and air pumps are used so that there is dissolved oxygen in the hydroponic system to ensure that even the fully submerged roots have access to oxygen.
In hydroponic systems, it is possible to overwater or even drown a plant. This happens due to the lack of an insufficient level of oxygen near the roots caused by overwatering.
There needs to be some specific level of dissolved oxygen in the water (equal or above 5 mg/L). To be safe, there should also be sufficient space between the water reservoir and grow tray to make sure that the roots are not all submerged so that they may intake oxygen.
Root rot can happen when roots are exposed to overwatered conditions which leave the roots lacking in oxygen. Root rot symptoms include, but are not limited to, yellowing of leaves, the slow growth of plants, the darkening of roots, and unhealthy leaf edges. Worse, fungi may grow due to these damp conditions which lead to the same effect.
Hence, root aeration is important in soil and hydroponic cultivation to make sure that the roots don’t “suffocate.” In hydroponics, root aeration is achieved through other means such as adequate spacing, air pumps, airstones, and/or mist pumps.
Overwatering in hydroponics can occur due to:
- Grow tray medium is too water-absorbent
- Water level is too close to the grow tray
- Air pump is too weak.
Let’s delve into each one of these problems.
In most hydroponic systems, the preferred mediums are often porous and strong to simply hold the weight of the plant and let the growing roots penetrate the medium and net cups in order to reach the nutrient rich water solution.
Generally, avoid anything that’s too water absorbent because wet growing medium means that there’s a high likelihood drowning to occur because the roots will not have enough oxygen to breath.
Related to the previous instance, overwatering can occur when the water level is too close to the grow tray. What will happen is that there won’t be enough dry area for the roots to intake oxygen
This is why there’s an adequate amount of space between the grow tray and the water reservoir in Water Culture systems. It’s specifically intended to give roots an area to intake oxygen.
This problem can be prevalent in Deep Water Cultures (DWC) since there won’t be enough dissolved oxygen in the reservoir to provide oxygen to the submerged roots.
As a general rule, the pump should be able to pump 1 LPM (liter per minute) for every liter in your system. Anything weaker may not produce enough dissolved oxygen in the form of “bubbles.”
As stated previously, hydroponic techniques differ on how they water the plant hence some techniques may be more prone to overwatering
Deep Water Culture (DWC) is a simple setup wherein the reservoir is oxygenated through the use of an air pump.
It is likely that overdrowning may occur in this technique if the all roots are submerged and there’s little space between the reservoir and the grow tray. If the air pump in conjunction with the airstones is too weak, it will not produce enough oxygen in the water in the form of bubbles.
This is a completely medium-free system. The roots are placed in slightly sloped channels and a continuous or periodic flow of nutrient solution streams.
Overwatering is an unlikely occurrence using this technique because the streaming water is too shallow to completely submerge all the roots.
Aeroponics uses nutrient-rich mist or fog operating 24 hours to provide hydration and nutrients to the suspended plants. The technique requires high technical knowledge and constant observation to make sure that the misters do not clog.
Because the entire plant itself is suspended and the nutrient solution is in mist form, the plant will not drown when using technique.
The ebb and flow technique waters the plants by periodically flooding and draining the flood tray/table where the roots are situated. This makes this system especially well-suited in hydroponically growing root crops such as turnips, carrots, potatoes, radishes, and beets, among others.
Overwatering is unlikely to happen here because the roots are periodically given enough air time to breathe.
The Wick is an easy technique to implement and recommended for beginners. It is a passive technique whereby active components are not necessary. The Wick system uses wicks to carry nutrients from the reservoir to the growing medium and growing tray.
The likelihood of overwatering is reduced in this technique because water drawn from the reservoir is proportionate to the plant’s consumption.
The Kratky technique is another easy technique to implement and a recommended option for beginners who are aiming for just small growing. The roots are placed directly over a stagnant nutrient rich reservoir.
The likelihood of overwatering can occur if there is not enough adequate room for the roots to breathe.
There are plenty of products of the analogue and digital variety to help make sure that watering, lighting, and even temperature are regulated.
Hydroponic growers would often use these timers to regulate watering, lighting, and heating devices to optimize plant growth depending on the specific plant variety’s growing requirements. These often come in the form of wall plugs which have additional outlets to
If you’re a fan of egg timers and analog media, a timer with a mechanical pin dial to set the timer for the device like this one here on Amazon.
For the tech-savvy grower, there are timers that have smartphone integration to set the parameters. Any extension cord is an unconventional device that does all of this despite being marketed primarily as an extension cord. It can be found here on Amazon.
- Like many living things, plants also require oxygen to survive. The roots and leaves intake oxygen for aerobic respiration.
- Overwatered roots can cause root rot, fungal infection, and anaerobic respiration. All these can cause plant disease and death.
- Properly implemented hydroponic systems will not drown the plants because not all the roots will be submerged. Timers can help in regulating the growing conditions of the plants.
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- “Aerobic and anaerobic respiration” by n/a in BBC
- “Aerobic Respiration” by n/a in Byju
- “Aerobic respiration: Proof of concept for the oxygen-centric murburn perspective” by Manoj et al in Journal of biomolecular Structure & Dynamics 37(17)
- “Basics of Plant Respiration” by Jose Chen Lopez in PREMIER HORTICULTURE
- “Dissolved Oxygen” by n/a in Fondriest Environmental Inc.
- “How do plants breathe?” by Mary F. Willson in Juneau Empire
- “Optimization of hydroponic growth system and Na+-fluorescence measurements for tree species Pongamia pinnata (L.) pierre” by Sureshbabu Marriboina Ramachandra and Reddy Attipalli in MethodsX Volume 7, 2020.
- “Plant respiration under low oxygen” by Guillermo Toro and Manuel Pinto in Chilean Journal of Agricultural Research 75(1)
- “Plant Roots” by n/a in Furman University
- “Respiration In Plants” by Nnaemeka Joe Okonkwo in Basic Biology
- “Roots” by n/a in Biology LibreTexts