Question

Coating urea with which of the following has been found to increase the yield of crops ?

• A. LIME
• B. Neem OIL
• C. Charcoal
• D. Cowdung

Hint:

Neem Coated Urea (NCU) is mandatory in India to reduce the diversion of subsidized agricultural urea for industrial purposes and to improve nitrogen use efficiency (NUE) by up to 10-15%.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Urea is a highly soluble nitrogenous fertilizer that is prone to rapid hydrolysis, leading to significant nitrogen losses through ammonia volatilization, nitrate leaching, and denitrification.
Coating urea with substances that slow down the nitrification process helps synchronize nitrogen release with crop demand, thereby improving nitrogen use efficiency (NUE) and crop yields.

Step 2: Detailed Explanation:
Neem oil contains bioactive triterpenoids, such as epinimbin, nimbin, and salannin, which act as natural nitrification inhibitors.
When urea coated with neem oil is applied to the soil, these compounds temporarily suppress the activity of nitrosomonas bacteria.
These bacteria are responsible for converting ammonium (\(\text{NH}_4^{+}\)) into nitrite (\(\text{NO}_2^{-}\)), which eventually oxidizes to highly leachable nitrate (\(\text{NO}_3^{-}\)).
By delaying this conversion, neem-coated urea keeps nitrogen in the ammonium form for a longer duration, reducing leaching and gaseous losses.
As a result, more nitrogen remains available to the root system over an extended period, which directly leads to improved vegetative growth, grain filling, and higher crop yields.

Step 3: Final Answer:
Coating urea with Neem OIL has been found to increase the yield of crops.