P for Phosphorus

This is with reference to the incisive article, “Addressing India’s Food Security: Is Phosphorus the Missing Link?” by Madhuri Nanda (EPW, 14 April 2018). Indeed, phosphorus (P) is as essential as water, carbon or oxygen. It is also a queer plant macronutrient because despite deficiency symptoms in plants such as retarded growth, stunted roots, pigmentation of leaves, etc, it is difficult to diagnose its deficiency. This apart, by the time the deficiency is recognised it may not recover even if P is applied later.

Chemically, P is a very stable element. Fertiliser P does not move from where it is applied because it quickly binds with iron and aluminium in the soil and becomes unavailable in plants particularly in acidic soil. As a result, crops can take only 5%–20% of the P applied to the soil. Of course, to ensure appropriate uptake of P by plants, soil testing is a must.