Why Your Irrigation Water Affects Your Media pH
May 23, 2018 
The media pH of your greenhouse crop can affect the overall health and quality of your crop. If the pH of the media is not within an acceptable range for the crop you’re growing, you may experience deficiencies or phytotoxicity depending on the crop and the macro or micronutrients affected.
“Often times I hear the comment that a particular crop’s pH is high and that the pH of the irrigation water is to blame, when in fact it is the alkalinity of the irrigation water that will tend to drive up the media pH”, says Nelson Gonzalez of ICL, a global manufacturer of fertilizer products.
The pH of your media is most affected by the alkalinity of your irrigation water. Irrigation water that is alkaline contains bicarbonates, and the more bicarbonates, the higher the alkalinity. As crops are irrigated over time, these bicarbonates will increase media pH.
When growers irrigate with alkaline water, they are essentially adding small doses of bicarbonates or lime to the media and therefore increasing the probability of elevating the pH of the media. This becomes even more important the smaller the pot size, as the pH can climb more rapidly in smaller containers.
In some cases, it is possible that irrigating with alkaline water may not affect the crop: bicarbonate levels may not be sufficient to increase the media pH, and with short-term crops, there may not be enough time for the pH to rise or the plant may be more tolerable to a high media pH and not display any symptoms. Nonetheless, monitoring and knowing the alkalinity of our irrigation water will help you be proactive and allow you to take measures that will prevent future challenges.
Keep this fact in mind and be sure to have your water tested in order to prevent these problems from occurring, especially if you suspect high alkaline irrigation water.
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