Why Water Quality Matters More Than You Think in Hydroponics

What is the ideal water quality for hydroponics. The answer is going to be very fluffy but one thing is certain, if you have pure distilled water or water that can be used for bottling it’s going to cost you a lot of money. Pure clean water is not ideal. If you are a scientist and you are testing the effect of various elements on plant growth it is best to start from scratch, but fertilizer is expensive and the more nature can provide you some for free, the better.

Water quality is one of the most important factors determining the quality of the crop in Hydroponics. You could say it is the foundation of the entire production system. You can grow crops far from the equator and supplement the lack of light with artificial light, but if you have low water quality there are no cheap options to remove pollutants.

The quality of that water affects nutrient availability which has an effect on crop health, yield, fruit quality and disease resistance. Growers focus on nutrient formulations, the water itself deserves just as much attention. A lot of growers have to compensate on fertilizer selection due to bad water quality.

Potable water is safe for human consumption and is completely clean and or safe. It will also have a very low electrical conductivity which is ideal but very expensive if used for farming. Thus, not economically viable. Water for hydroponic systems does not have to be so clean, but, the EC should be as low as possible so there is ample space for adding adequate nutrients. Also there should be no micro-organisms or organic matter that can affect the plant.

From a nutritional perspective, water with low levels of dissolved salts is generally preferred. Low electrical conductivity (EC) provides growers with greater flexibility when preparing nutrient solutions and reduces the risk of unwanted salt accumulation in the root zone. Likewise, low bicarbonate concentrations make it easier to maintain a stable nutrient solution pH without excessive acid additions. For this reason, many extension guides and greenhouse production standards define acceptable limits for EC and specific ions, with the Dutch greenhouse water quality standards often regarded as one of the most comprehensive references available.

I think a lot of growers understand why water quality is important from a nutrition standpoint, the organic or biological side has been overlooked because it’s so difficult to control and analyse. The wrong organic material can devastate a complete farm, while low water quality won’t.

The dreaded species that can wreak havoc and often found in water reservoirs are Pythium, Rhizoctonia and Fusarium. These pathogens have all been identified in rainwater storage tanks. Pathogen spores may enter these reservoirs through wind blown dust, splashing rain, or infected plant debris (a major culprit). Once established, they can spread rapidly through recirculating irrigation systems if no treatment is applied.

Algae are amazing plants if grown at the right place. They are often used to remove significant portion of pollutants in water, thus can be used as a filter to lower EC levels. Algae growth in the nutrient solution causes a lot of different problems. They can be a real nuisance when drippers and filters are clogged, restricting water flow. Under favourable conditions, algae can produce large amounts of sticky mucilage in a relatively short period, reducing irrigation uniformity and increasing maintenance requirements. Certain algae and cyanobacteria may also release compounds that interfere with normal plant growth. These compounds are referred to as allelopathic chemicals.

Its not all doom and gloom, some naturally occurring bacteria appear to benefit crops by stimulating root development or suppressing disease-causing organisms. Species of Pseudomonas and Bacillus, for example, have been associated with improved root health and biological control of several important pathogens. Note that not all bacteria are bad. Some are beneficial for plant growth. One of the most important fungi, rhizobium is crucial for good root growth.

Farmers use rainwater, groundwater, municipal supplies and surface water. It really just depends on the geographical terrain of the farm. Rainwater is often considered the preferred option because it usually contains very low concentrations of dissolved salts and relatively few microorganisms when freshly collected. This gives growers greater control over nutrient formulation and reduces the need to compensate for unwanted ions already present in the water.

The challenge is that rainwater quality does not always remain constant after storage. Open reservoirs may gradually accumulate nutrients, algae and microorganisms, while atmospheric deposition can introduce additional contaminants. Rainfall is also seasonal, and storage capacity or collection efficiency may not always be sufficient to meet irrigation demand. During these periods, growers often supplement with surface water or other available sources, although these may carry higher salt loads or greater biological risks.

To better understand these differences, researchers monitored both rainwater and surface water over a full year, evaluating not only their chemical composition but also their bacterial populations and algal development. Their findings provide valuable insights into how different water sources may influence hydroponic crop production and reinforce the importance of monitoring both the chemical and biological aspects of irrigation water rather than focusing on nutrient concentrations alone.