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.

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. The chart below shows more common nutrient antagonisms.

Nutrient in Excess

Induced Deficiency

NH4, K, Ca, Mg, Na

K

K and / or Ca

Mg

Cl

NO3, SO4

N

K

Ca

Mg

Mg

Ca

Ca

B

PO4

Fe, Mn, Zn, or Cu

Fe

Mn

Mn

Fe

Mo

Cu

Legend

Symbol

Nutrient

B

Boron

Ca

Calcium

Cu

Copper

Cl

Chlorine

Fe

Iron

K

Potassium

Mg

Magnesium

Mn

Manganese

Mo

Molybdenum

Zn

Zinc

NO3

Nitrate

SO4

Sulfate

PO4

Phosphate

NH4

Ammonium

David Kessler heads research and development at Atlantis Hydroponics and writes for their popular blog. David has over two decades of experience and multiple degrees from the State University of New York. He’s also an accredited judge for the American Orchid Society and travels the world judging orchid events. Follow his blog at atlantishydroponics.wordpress.com