Nitrogen cycle in the soil

While nitrate is taken up directly by plants, ammonium and urea first need to be transformed into nitrate. Transformation losses are lowest with nitrate and highest with urea. All the nitrogen in the soil, whether it was applied as urea, ammonium or nitrate, ends up as nitrate before plants take it up. 

If nitrate is applied directly, then losses from the transformation from urea to ammonium and ammonium to nitrate are avoid

Understanding Nitrogen Efficiency

With 46% N content, Urea is the most popular Nitrogenous fertilizer around the world. When Urea is applied to soil, it is first hydrolysed (i.e. broken by water)  into Ammonical form (Ammonium Ion i.e. NH4+) and then to nitrite (NO2-), followed by to nitrate (NO3-) forms by the process called nitrification. Here, we note that most crops use nitrate as source of nitrogen (A few crops such as Paddy prefer Ammonical form over nitrate.).

Thus nitrification process is necessary for making nitrogen available to plants. However, if the process of nitrification is too rapid; nitrogen will escape to atmosphere and plants will not be able to recover it from Urea efficiently. Generally, the plants are able to recover a fraction of all Urea N  and this fraction is known as Nitrogen Use Efficiency (NUE). This NUE stands anywhere between 30 to 50%. Thus, two third of Urea Nitrogen escapes from the soil and is not used by the plants. Further, faster conversion of nitrate into Urea also results in accumulation of nitrates in soil / underground water. Once nitrate reaches underground water, it is most difficult to remove; and causes diseases such as blue baby syndrome.

This implies that there is a need to regulate the urea hydrolysis and nitrification. This is done by some chemical / natural agents which are called Nitrification inhibitors. However, most of the nitrification inhibitors are costly chemicals (examples nitrapyrin, dicyandiamide and ammonium thiosulphate ) beyond reach of Indian farmers. Coating Urea with Neem oil or Neem cake has been proved to be an effective natural alternative to these chemicals. It has been scientifically established that Neem oil serves as an effective inhibitor if coated on Urea.  Thus, the benefits are as follows:

• Neem coating leads to more gradual release of urea, helping plants gain more nutrient and resulting in higher yields.
• Lower underground water contamination due to leaching of urea.
• Neem serves as a natural insecticide
• Collection of neem seeds is needed for manufacturing of neem coated urea. This would generate employments in rural areas.
• Neem-coating will help check heavily subsidized urea’s pilferage to chemical industry and other uses such as making of adulterated milk.

Government Policy on Neem Coated Urea

In January 2015, the government allowed the urea producers to produce up to 100% of production as Neem coated urea. Further, the government made it mandatory to produce at least 75% of domestic Urea as Neem coated. The current policy is that Government has mandated all indigenous producers of Urea to produce 100% of urea as Neem coated urea only.