When it comes to irrigation water and water quality, you’ve probably heard the terms pH, alkalinity, and bicarbonates threw around. Many growers focus on pH targets when adjusting their irrigation water. This is likely based on the fact that there is an optimal pH range for growing media that allows for the solubility and uptake of all essential plant nutrients.
The problem with targeting pH when adjusting irrigation water is that it’s a relative reading that doesn’t give us a clear picture of how the water will tolerate the addition of acid or base to the system. The Acid Neutralizing Capacity (ANC) or Alkalinity will dictate that.
When the pH of growing media is too high, most micronutrients become unavailable, and there is a risk of nutrient deficiencies. When addressing water quality and the need for acid, we tend to focus on bicarbonate ions since this is the most prevalent ion in typical sources of fresh water.
When bicarbonate levels are too high, they can react with calcium and magnesium to form bicarbonate salts, further increasing media pH and removing vital nutrients from the solution.
When bicarbonate levels are too low, such as in the case with Reverse Osmosis water, there is no buffering capacity, allowing inputs to have a strong impact on pH, typically resulting in significant swings in media pH. This can be remedied by adding potassium bicarbonate to your filtered water.
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