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Importance of Dissolved Oxygen in Water

Although I have written about this before, it’s so important, that it deserves mention again – Dissolved Oxygen in water (DO).

While water from most sources is low or more often than not actually totally depleted of oxygen (the water is dead), oxygenated water has a lot of benefits. DO is in fact one of the best indicators of the quality, and the life-supporting ability, of water.

There is a lot to talk about with regard to water quality and DO, but I will keep this relevant to the 2 most common water sources – municipal water supplies via a reticulated system of pipes from dams, aquifers or other sources, and bores and wells.

All of these sources tend to be extremely low or totally depleted of DO. For many uses, such as flushing toilets, doing dishes etc that doesn’t make much difference. Dead water does the job just fine. However there are things that will substantially benefit from high levels of DO in the water. It’s nature’s way.

Why do gardens/plants generally do much better from rain, than if being irrigated? The big difference is DO. Rain water is saturated with DO.

It is not just us humans and air breathing creatures that require oxygen to survive. Fish need dissolved oxygen in water and so do plants. Increased levels of DO in water can substantially increase root mass and therefore growth and health of plants.

At levels around 5 mg/l of dissolved oxygen, irrigation water is typically considered marginally acceptable for plant health. Most greenhouse crops, however, will perform better with higher levels. Levels of 8 mg/l or higher are generally considered to be good for greenhouse production and much higher levels, as high as 30 mg/l or more, are achievable and can be beneficial. If DO levels are below 4 mg/l, the water is hypoxic and becomes very detrimental, possibly fatal, to plants and animals. If there’s a severe lack of DO, below around 0.5 mg/l, the water is anoxic. No plants or animals can survive in anoxic conditions. The irrigation water in many greenhouses has surprisingly low levels—often in the dangerous hypoxic range.

Boosting dissolved oxygen levels in water can increase plant growth and health, but also reduce the need for fertilisers and pesticides, if that’s what you use.

Of course all that does not only apply to greenhouses, but plants in general. If you are growing fruit and vegetables, having good levels of DO in your water will help with better, healthier and more nutritious crops.

There are a number of factors that affect the maximum levels of DO water can hold.

Dissolved oxygen levels are affected by the temperature and salinity of the water, and also by other chemical and/or biological demands of the water. Cold water can hold more dissolved oxygen than warm water and fresh water can hold more dissolved oxygen than salt water.

How do you increase DO in water? There are many ways to aerate water and the method used may depend on your water source.

You may put a venturi in the water pipe going to your plants to suck in air. If water is stored in a tank, put an aerator in there. If water is good enough to be tolerated by the plant’s foliage, sprinklers can help water draw in DO as it is sprayed over the plants, although a lot of water may be lost due to evaporation.

So, we tend to take water for granted. We maybe worrying about chemicals and impurities, but dissolved oxygen can be just as important.

More information is available at

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sm badsha
sm badsha
Jun 09, 2022


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