Question

A farmer adds/ supplies Na, Ca, Mg and Fe regularly to his field and yet he observes that the plants show deficiency of Ca, Mg and Fe. Give a valid reason and suggest a way to help the farmer improve the growth of plants.

Answer 1

Plants require macronutrients in deficient amounts. Any increase in this limit may result in toxicity because of the high level of a particular nutrient. In this case, the plants may be suffering from manganese toxicity. Most farmers use broad-spectrum fertilizer. Most broad-spectrum fertilizers contain manganese. Manganese competes with iron and magnesium for uptake and with magnesium for binding. It also inhibits calcium translocation shoot apex. Hence, excess manganese may induce Ca, Mg, and Fe deficiency.

Cure for manganese toxicity in plants:

1. Manage water efficiently. Mn absorption may be accelerated under the condition of surface drainage.
2. Balance the use of fertilizers (NPK or NPK + lime) to avoid nutrient stress as a source of Mn toxicity. Apply lime on acid soils to reduce the concentration of active Mn.
3. Do not apply excessive amounts of organic matter (Manure, straw) on soils containing large Mn and organic matter concentrations and poorly drained soils.