Plant Problem Diagnosis Key / Nutrient problems
pH out of range (nutrient lockout)
pH
Outside the right pH range, nutrients that are present cannot be taken up, so the plant shows several deficiencies at once even on a complete feed. Iron, manganese, zinc and boron go first at high pH; potassium, calcium and magnesium at low pH.
Signs
- Mixed symptoms that match more than one deficiency.
- Symptoms that continue after the feed is raised.
- Root-zone pH outside about 5.5-6.5 in hydroponics, 5.4-6.2 in soilless mixes, or 6.0-7.0 in most soils.
What favors it
Unadjusted feed water, high-bicarbonate water, acidic or alkaline amendments, and media that drifts over time.
Prevention
- Test water alkalinity and adjust feed pH.
- Check runoff or slurry pH weekly.
- Lime acidic soils and acidify alkaline ones per a soil test.
Often confused with
Sources
- HO-237: pH and Electrical Conductivity Measurements in Soilless SubstratesPurdue Extension
- Identifying Nutrient Deficiencies in Ornamental PlantsUniversity of Delaware Cooperative Extension
- Nutrient Deficiency of Vegetable PlantsUniversity of Maryland Extension
Treatment by crop
Cultural, biological and chemical options in the order to use them, and notes written for each crop.
Identification is free. Treatment is on the Home and Pro plans.
Questions in the key that lead here
- Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
No, only damage or discoloration - Where is the problem?
Leaves - What does the leaf damage look like?
Color change without distinct spots - Where did the color change start?
Across the whole plant, or in patches - What does the change look like?
Several symptoms at once, and the feed looks right
Not a match? Start the key or describe what you see.
More photos
More from university Extension: search Extension pages on ph out of range, or find a plant diagnostic lab through your state's Extension.