Watering, Feeding & Nutrients
pH
pH measures how acidic or alkaline a substance is, such as water or a growing medium. In cannabis cultivation, proper pH is critical because it determines whether nutrients can be absorbed by the roots.
What pH Means in Plant Growing
pH is a scientific scale used to measure the acidity or alkalinity of a solution, ranging from 0 to 14. A pH of 7 is considered neutral, values below 7 are acidic, and values above 7 are alkaline. In cannabis cultivation, pH most commonly refers to the acidity level of water and the root zone, both of which directly affect nutrient availability.
How pH Affects Nutrient Availability
Nutrients must be dissolved in water and present within a specific pH range to be absorbed by plant roots. If pH falls outside this optimal range, nutrients may still be present in the growing medium but become chemically unavailable to the plant. This condition is known as nutrient lockout and often leads to deficiency symptoms even when feeding is adequate.
Ideal pH Ranges for Cannabis
Cannabis plants generally prefer slightly acidic conditions. In soil-based systems, the optimal pH range is typically around 6.0 to 7.0, while soilless and hydroponic systems perform best in a narrower range around 5.5 to 6.5. Deviations outside these ranges can interfere with the uptake of key nutrients such as nitrogen, phosphorus, calcium, and magnesium.
Scientific Understanding of pH
The importance of pH became widely understood through agricultural and plant science research in the 19th and 20th centuries, when scientists discovered that nutrient absorption depended not only on nutrient presence but also on chemical conditions in the root environment. This knowledge led to modern cultivation practices that emphasize regular pH testing and adjustment.
Managing pH in Cannabis Cultivation
In cannabis cultivation, pH is managed by testing water, nutrient solutions, and runoff, then adjusting as needed using pH-up or pH-down products. Stable pH supports efficient nutrient uptake, healthy root function, and consistent plant growth, while unstable pH is a common underlying cause of persistent growth problems and reduced yields.
Related terms:
Nutrient Uptake, Nutrient Lockout, Root Zone, Watering, Fertilizer, Growing Medium, Soil pH, Runoff
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