pH

pH is a logarithmic scale used to specify the acidity or alkalinity of a solution, ranging from 0 (highly acidic) to 14 (highly alkaline), with 7 being neutral. In controlled growing environments, pH management is fundamental because it governs the solubility and availability of nutrients to plant roots.

Why pH matters: Most essential nutrients are only available within a specific pH range. Outside this range, nutrients become chemically locked in forms that roots cannot absorb, even if the nutrients are physically present in the solution. This causes deficiency symptoms that mimic actual nutrient shortages.

Optimal pH ranges by growing system:

• Hydroponics (inert media: rockwool, coco, NFT): 5.5-6.2
• Soil and soil-like media: 6.0-7.0
• Coco coir: 5.8-6.3

Common pH adjustment products:

• pH Down: typically phosphoric acid, used to lower pH
• pH Up: typically potassium hydroxide or potassium silicate, used to raise pH

Monitor pH at least daily in recirculating systems, and with each feed in run-to-waste systems. pH naturally drifts upwards in most hydroponic systems as plants absorb nutrients. Small, controlled fluctuations within the optimal range (sometimes called 'pH swings') can help ensure a broader spectrum of nutrients remains available.