Nutrient lockout occurs when plants are unable to absorb one or more minerals from the growing medium or nutrient solution, despite those nutrients being physically present. It is most commonly caused by incorrect pH, excessive EC, or antagonistic interactions between mineral ions that block uptake.
Key Facts
- Most common cause: pH outside the optimal range (5.5β6.5 in hydroponics)
- High EC can create osmotic stress that prevents water and nutrient uptake
- Mineral antagonism: excess calcium blocks magnesium; excess phosphorus blocks zinc and iron
- Symptoms mimic deficiency β yellowing, curling, or discolouration β despite adequate nutrients
- Fix: flush roots with pH-balanced plain water, then reintroduce nutrients at correct pH and EC
- Prevention: test pH and EC daily; change reservoir solution every 2β3 weeks