Context

Although, Nano Urea (a fertilizer) has been approved by the government for commercial use but several experts have questioned the science underlying its efficacy.

About

What is Nano Urea?

• It is urea in the form of a nanoparticle. It is a nutrient (liquid) to provide nitrogen to plants as an alternative to conventional urea.
• Urea is chemical nitrogen fertilizer, white in colour, which artificially provides nitrogen, a major nutrient required by plants.

Why farmers opt for nanourea?

• It is developed to replace conventional urea and it can curtail the requirement of the same by at least 50%.
• It allows more absorption than conventional urea as it has nano particles which consequently absorbed more by the plants.
• The small size (20-50 nm) of Nano Urea increases its availability to crop by more than 80%.

How does nano urea work?

• When sprayed on leaves, Nano Urea easily enters through stomata and other openings and is assimilated by the plant cells.
• It is easily distributed through the phloem from the source to sink inside the plant as per its need.
• Unutilized nitrogen is stored in the plant vacuole and is slowly released for proper growth and development of the plant.

Why have experts raised questions about the efficacy of Nano Urea?

• Discrepancy in the percentage of available nitrogen: Chemically packaged urea is 46% nitrogen which means a 45 kg sack contains about 20 kg of nitrogen. Contrastingly, Nano Urea sold in 500 ml bottles has only 4% nitrogen (or around 20 gm).
  • This discrepancy in the percentage of available nitrogen has left many experts puzzled.
• Effectiveness of nitrogen uptake is questionable: Urea is highly water soluble and already reaches the lowest form of concentration when absorbed.Foliar spraying (spraying on leaves) improves fertilizer uptake is known for over half a century.
  • Even if 100% of 20 gm of Nano Urea, which is what is effectively available, is utilized by the plant, it will yield only 368 gm of grain. Therefore, the total attempt is futile causing sheer wastage of money.
• Incidence of increase in yield is superfluous: Some experts say that, in the first year of application of nano urea, the nitrogen present in the soil and fertilizer was already sufficient, and supplying nitrogen via Nano Urea was superfluous.

What is the counter-argument?

• Conventional forms of urea when fall on the soil, all the nitrogen present in that granule, typically 1-2mm in size, becomes available readily to the crop. But because of burstrelease, the ammonia escapes into the environment, reacts with oxygen in the environment, and becomes nitrous oxide which is a greenhouse gas.
• On the contrary, nano-urea is sprayed on the plant leaf. These are particles of 20 to 50 nanometers. They get readily absorbed by the plant, and release nitrogen inside the plant.
  • They also stimulate the enzymes involved in nitrogen metabolism inside the plant cells and boost the protein content, chlorophyll content,and the nucleotides such as RNA content or DNA content.