Discretionary use of urea

Urea or carbamide is an organic compound with the chemical formula CO(NH2)2. The molecule has two —NH2 groups joined by a carbonyl (C=O) functional group. It serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals. Dissolved in water, it is neither acidic nor alkaline. The body uses it in many processes, the most notable one being nitrogen excretion. Urea is widely used in fertilizers as a convenient source of nitrogen. Urea is also an important raw material for the chemical industry.

The discovery by Friedrich Wöhler in 1828 that urea can be produced from inorganic starting materials was an important conceptual milestone in chemistry Farmers often use nitrogenous fertilizers (mostly urea) or nitrogenous and complex fertilizers (mostly urea and DAP), ignoring the application of potash and other deficient nutrients. This results in decline in soil fertility status. Soil analysis in India under different projects reveals widespread deficiency of at least six nutrients viz., Nitrogen (N), Phosphorus (P), Potash (K), Sulphur (S), Zinc (Zn) and Boron (B).

Urea, being most common N fertilizer, is indiscriminately used irrespective of scientific prescriptions. Excessive use of urea leads to several adverse implications on soil, crop quality and overall ecosystem. It enhances mining of soil nutrients that are not applied or applied inadequately, thus leading to deterioration of soil fertility. Such soils may require more fertilizers over time to produce optimum yields.

Excessive use of N (urea) encourages climate change (when lost through denitrification) and groundwater pollution (when lost through leaching). Urea application should be invariably balanced not only with P and K but also with deficient secondary and micronutrients; soil test-based fertilizer prescriptions have to be adopted. Farmers should insist for S and micronutrient testing, as NPK alone (without S and micronutrients) is no longer balanced fertilizer prescription.Neem oil coated urea should be preferred over pilled urea, especially for basal dressing. Losses of N are usually less when urea is top-dressed before irrigation.