It is possible that feeding an excess of nutrients to your plant can still result in deficiencies. This is because sometimes plants suffer from “nutrient antagonism.”
Nutrient antagonism is when an excess of a particular element blocks the absorption of another element the plant needs and can happen with elements of a similar size and charge (positive or negative).
Some of the most common antagonisms are iron blocking manganese (or the reverse), magnesium blocking calcium (or the reverse) and potassium blocking both magnesium and calcium.
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Another reason for a plant being deficient in an element applied in an appropriate dosage is called binding. Binding occurs when elements mix together and bond, forming a compound that is insoluble and cannot be absorbed by a plant’s roots.
This is seen when concentrated acids or bases are mixed into nutrient solution and a cloud of precipitate forms. The precipitate, or milky cloud that is formed, is the result of elements binding and becoming unavailable to the plants.
Binding may also occur when iron or zinc is mixed in a solution of phosphates (HPO4-2) and a mineral called strengite forms.
This compound is completely insoluble and will make both the phosphorous and the iron or zinc unavailable to plants.
A heavy flush with plain pH adjusted water, followed by an application of fresh nutrient solution can usually solve both of these types of issues.
Common Nutrient Antagonisms
Nutrient in Excess | Induced Deficiency |
Ammonium (NH4), Potassium (K), Calcium (Ca), Magnesium (Mg), | Potassium (K) |
Potassium and/or Calcium | Magnesium (Mg) |
Chlorine (Cl) | Nitrate and Sulfate |
Nitrogen (N) | Potassium |
Calcium (Ca) | Magnesium (Mg) |
Magnesium (Mg) | Calcium (Ca) |
Calcium (Ca) | Boron (B) |
Phosphate (PO4) | Iron (Fe), Manganese (Mn), Zinc (Zn), |
Iron (Fe) | Manganese (Mn) |
Manganese (Mn) | Iron (Fe) |
Molybdenum (Mo) | Copper (Cu) |
