Foliar application of Nano Urea - few questions ? (Article no 39)

 Shri Ravindra Thatte,

Director,

Eco Agro Group, Pune.

It is well known that:

1. More fertilizers have to be used to get the same yield as in past.
2. Government of India would like to reduce overuse / dependence of farmers on Urea. Looking at the skewed NPK fertilizer ratios, there is no doubt that usage of Urea in India should be reduced as it is the largest selling and cheapest Nitrogen source.
3. Urea is polluting and responsible for production of NOx and NH4 emission and oxidizing of organic matters when applied via soil.
4. Due to its low price and high N content (46% of the mass), Urea is the most used N fertilizer in India.
5. Foliar fertilizers have very high use efficiency and are generally considered to be 10-20 times more efficient than soil application.  
6. Urea has low fertilizer use efficiency (FUE) of about 30% (when applied via soil). However, Tamilnadu Agriculture University (TNAU) publication says that, the efficiency of Urea when applied as fertigation (by drip) is 80 -90 %. Efficacy of granule Urea applied via foliar also must be at least as high or could even be 100%. Foliar fertigation is always considered to be a supplement or compliment to the soil application.    

Nano Urea (NU) - Misinformation/ Misinterpretation:

1.   1 bag of granular Urea (45kg) is said to be equivalent to a 500 ml bottle of Nano Urea. 

2.     Soil application is compared with foliar application, which is scientifically wrong & misleading. Both the product and the treatments are different in this Comparison.

a)   Soil applied Urea cannot be compared to foliar applied Nano Urea. Comparison of foliar applied Nano Urea (NU) should be with other foliar applied Nitrogen sources for example: 1 % Urea solution (which is an age old recommendation/practice and gives excellent results).

·  It is not known if any comparison of Nano Urea is done with 1 % or higher concentration of normal Urea Solution or with low biuret Urea solution at various concentration and its C:B ratio. 

b)    There is deliberate attempt of obfuscation and confusion by comparing particle size of normal granular Urea meant for soil application with liquid Nano Urea to be applied via foliar application. That’s why comparison of particle size is meaningless [as per IFFCO website https://nanourea.in/en/nano-urea: - Nano Urea has a desirable particle size of about 20-50 nm and more surface area (10,000 times over 1 mm Urea prill) and number of particles (55,000 nitrogen particles over 1 mm Urea prill size of normal granular Urea ]. 

c)     Even in case of soil application, Urea Prill / granule is not taken up by the root directly. It is first dissolved in water to form a solution and then transformed into NH₄ Nitrogen or NO₃ Nitrogen before it is taken up by plant.

3.     Comparison of Nano Urea foliar application should have been done with N sources Such as 19:19:19, 13:0:45 etc.?

a) Water soluble 19:19:19 is an amazingly effective fertilizer widely used by farmers. 19:19:19 applied at recommended dose of 5 gram/ litre x 200 litres of water / acre = 1 kg / acre will cost about Rs 150 per kg and will supply 190 g N + 190g P + 190 g K respectively. Further Nitrogen will be in 3 forms – Urea, Ammoniacal and Nitrate.  This product is very effective and cost economical. Is there any comparative data?

4.     Nano technology and particle size. 

a)     Many persons do not realize that the Nano particle size is bigger than Ionic form present in a Urea Solution.  It may be noted that, Urea is completely soluble in water and Urea solution is ionic (i.e. it will not be particles) and have molecular size smaller than Nano.

·    There is no restriction to entry of normal Urea molecule through the leaf cuticle or stomata of leaf either due to chemistry or due to size of molecule.

·    IFFCO website https://nanourea.in/en/nano-urea: states that, Nano Urea can easily penetrate through the cell wall or through leaf stomatal pores. After entering the plant, they are transported to other plant parts via phloem cells, plasmodesmata (40 nm diameter) or can bind to carrier proteins through aquaporin, ion channels and endocytosis). As if this is exclusive for Nano Urea?

·    Foliar applied Urea solution is completely absorbed by leaf and becomes available to plants to form amino acids.

·     There is no scientific evidence of comparison between entry, absorption, assimilation between normal granular Urea solution and liquid Nano Urea to support the contention of IFFCO that Nano Urea has superior property of absorption and assimilation.  

·        So, the particle size comparison is spurious and misleading.   

b)    As per published information, Nano Urea contains 4 % N. Recommended application of foliar Nano Urea is @ 500 ml /acre, which means if all the Nano Urea spray material falls on the leaves in the canopy, and all droplets are retained on leaves, and absorbed in entirety by the leaf, only 20 gram of Nitrogen compound (form of nitrogen not disclosed) will be absorbed by the crop. This type of spray efficiency is not possible by any spraying equipment at this time.

IFFCO claims that due to Small size (20-50 nm) of Nano Urea, availability to crop increases by 80 %. Does it mean that 80 % of 20 gram = 16 gram of Nitrogen becomes available to plant?

·   How much of Nitrogen from normal granular Urea solution become available to plant?

·    Is there any study to show this comparison?

·   Are there any labelled N15 studies to compare absorption, assimilation of N from Nano Urea and granular Urea solution?

Table: Comparison of application (spray volume/acre), N product, % nutrient content, Net cost at retail price is presented here for easy comparison of cost.

e) Is Nano Urea beneficial product for Indian farmers? Cost of non-subsidized Urea is Rs 5.5/kg and that of non-subsidized is Rs 18/kg.  Does Nano Urea give respectively 2081 % or 566 % higher yield if compared with cost of subsidized or non-subsidized Urea as 1 % solution?

f) To protect the interest of Indian farmers IFFCO and mainly our scientific institutions should answer this question.

5.     Scientific explanation how 20 gram of nitrogen from Nano Urea is providing superior yield as compared to One 45 kg bag granular Urea through soil applied Nitrogen (in spite of 103400 % lower nitrogen content).

a)     Scientific explanation how 20 gram of nitrogen from Nano Urea is providing superior yield as compared to 920 grams of Nitrogen through 1 % foliar application of granular Urea when it is supplying 4500 % lower nutrient content. 

b)    25kg & 20kg of Nitrogen is required to produce yield of wheat and rice respectively (Which actually means that, 70% more is to be applied to the soil). The Nitrogen taken by the plant is assimilated and utilized in the growth of leaf, roots, stem and branches, flowers etc. and also stored in the grains as protein.

·     Of the 20 Kg of Nitrogen take up by rice to produce 1 ton of grain yield, 10 is found in grain , 6 in straw, and remaining may be in underground roots. Thus the Nitrogen taken up by the plant is converted to amino acids and proteins and stored in grains as proteins. Thus, substantial Nitrogen is essential for growth of plants and it is only a matter of efficiency & availability.

·    As per published research there is no difference between Nano Urea or Normal Urea, once it enters into the plant and it assimilated in the plant by the same mechanism (GS/GOGAT pathways) into proteins, nucleic acid etc.

·      How does IFFCO / scientific institutions explain mass balance? In other words how 20 gram of nitrogen become equivalent to N content of 1 bag of Urea?

·  This is the main question and without sufficient data the claim is just disinformation and marketing hype or hoax for which GOI (Government of India) has fallen.

·      PAU (Panjab Agriculture University) research has shown negative growth after application of Nano Urea

Ø   PAU director of research Dr. Ajmer Singh said their field trials so far have not come up with the results claimed from Nano Urea, especially in terms of the overall crop yield and nitrogen content in grains. The trials were initially conducted on wheat, though Nano urea was being tested on other crops as well.

Spray of urea in 1.5%-2% concentration would be more effective” (Reference – www.timesofindia.indiatimes.com - Field trials make PAU doubt ‘nano urea benefits’ claims. Vibhor Mohan / TNN / Updated: Aug 30, 2023) 

Ø   There was a 21.6 per cent decrease in wheat yield and a 13 per cent decrease in rice yields with the use of nano urea, the researchers found. The study was done in 2020-21 and 2021-22 by Rajeev Sikka, senior soil chemist and Anu Kalia, assistant professor, nanoscience, at PAU. The experiment revealed that the above-ground tiller biomass and root volume was lesser in the application of nano-urea (Reference: www.Downtoearth.org.in -  Dip in yield, low protein content: PAU field experiment finds several problems with nano urea. by Shagun Published on Wednesday 03 January 2024)

Ø   Similarly, international scientists has also questioned the claims of IFFCO. (Reference: Is India’s largest fertilizer manufacturer misleading Farmers and society using dubious plant and soil science? Opinion paper By Max Frank, Soren Husted published 10 August 2023. https://link.springer.com/article/10.1007/s11104-023-06191-4.   

c)   Are there any crop log studies exclusively using Nano Urea which show 1 Bottle of 500 ml liquid Nano Urea is equivalent to 1 bag of Granular Urea?     

6.  If it is really equivalent, then why IFFCO’s recommendation for crops does not advocate use of 1 less bag of Urea? The recommendation advises 2 sprays of Nano Urea which in a way admits that, there product (500 ml of Nano Urea) definitely does not supply 1 bag of equivalent of Nitrogen (leave alone 2 bag). Does it not increases cost of production to farmers?

a)     Further granular Urea is placed in soil as basal dose or top dressing to become available to the plant when it is most needed during period of maximum growth, tillering, and flowering. Large amounts of nitrogen are required every day at this point of time for grand growth / tillering which simply cannot be supplied by few grams of nitrogen from foliar applied liquid Nano Urea.  

b)    Whereas, Nano Urea sprays are recommended at (1) active tillering/branching stage (2) 2nd spray: 20-25 days after 1st spray or before flowering in the crop.

c)     Note that the recommendation specifically advises that– Don’t cut off basal nitrogen supplied through DAP or complex fertilizers (Reference - IFFCO website:  https://nanourea.in/en/nano-urea)

7. Nano Urea Contains polysaccharides (carbohydrates). May be, it is the polysaccharides which is responsible for results and not Nano Urea. Has this aspect been evaluated? When N content is low, why it should not be called Biostimulant?

8.     Under FCO, patented products are not allowed. No products are registered by Brand name. Yet IFFCO claims that their product is patented.

9.     Further, it must be highlighted that specifications of Nano Urea liquid as given by Gazette Order S.O. 885(E): Total nitrogen % by weight: 1-5 %. How can FCO allow 500 % Tolerance for active Ingredient only for this product? 

10.     The form of Nitrogen present in Nano Urea is not even mentioned in FCO.

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