What is Nutrient Lockout?
"Nutrient lockout" is a type of nutrient imbalance that most commonly results from using too much fertilizer. When the concentration of nutrients is too strong the roots of the plant can become blocked from absorbing them. You can avoid nutrient lockout by monitoring plants for signs of nutrient deficiency and by monitoring soil and water with a pH meter. Hard water nutrient lockout can occur, so be sure that your water source does not have minerals that are interfering with fertilizer formulations or adding excess micronutrients.
Diagnosing Nutrient Lockout
Nutrient lockout can be hard to identify because it looks similar to other nutrient deficiencies. When diagnosing plant problems, take note of the physical signs of nutrient lockout like stunted growth, flimsy plants, and yellowing or curling of the leaves.
Next, check the pH of the soil and the water used for irrigation and nutrient mixing. For hydroponic growers, pH should be between 5.5 and 6.5. For soil, 6.0 to 6.8 is an appropriate pH.
Finally, check the content of the nutrients you have been feeding your plants and compare them to other cultivation data online to see if your nutrient schedule could be off. Strains have different preferences, and you could have some extra-picky plants on your hands.
Correcting Nutrient Lockout
Nutrient lockout most commonly occurs during vegetative growth, especially when switching over to floral growth and a new nutrient schedule. Flushing can be used to help correct nutrient lockout and soil nutrient build-up, and then a new nutrient formulation that is less concentrated can be used. You may also need to use a pH buffer, or pH correcting product like pH Up or pH Down. Cal-Mag is another nutrient correction product that is commonly used when water needs additional calcium and magnesium added.