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Urea Grades for Agriculture

Urea Grade A and Grade B for Agriculture

It is customary to divide different grades of Urea by field of use; for agriculture, Grade B is considered more suitable, while for industry Grade A is preferred.

In this article we will look at what exactly the difference is between these grades for agricultural application.

The main difference turns out to be in an indicator called Biuret.

Biuret is a standard by-product compound formed during urea synthesis. It is the amide of allophanic acid, an organic compound of the form C2H5N3O2 + H2O. For agriculture, it is essential that the Biuret content in Urea not exceed 1.4%, since at higher content it has a toxic effect on crops and acts as a herbicide. For this reason, urea is not recommended to be applied immediately before sowing. It is usually applied 1-2 months before the intended sowing date. Biuret decomposes on its own in the soil, releasing ammonia, within 10-15 days.

Main indicators:

From the practical experience of agricultural producers, with a biuret content below 0.8% (Urea Grade A, premium grade), no negative effect on plant development has been detected at all. For this reason, such urea can be applied to the soil immediately before planting.

Research.

Conducted experiments show that a biuret content of more than 3% applied before sowing negatively affects crop growth. For example, for citrus crops the toxic effect is noticeable at a biuret concentration of 2.5%, for spring wheat — 5%, for corn — 5.3%, for flax — 3%. Also, for citrus crops, for foliar feeding, urea can be used as a liquid solution with a biuret concentration of no more than 0.3%.

In granulated urea, the biuret concentration is no more than 1.4%. Such a concentration does not cause a negative effect on plant development, regardless of the timing of urea application.

Experiments have shown that biuret content in urea below 2.7% did not cause any noticeable negative effect in any case. Also, at a concentration of 5.3%, a negative effect is clearly visible on potatoes, corn, and sugar beet.
At the same time, when such a fertilizer was applied 3 weeks before sowing, there was no negative effect on corn at all. This occurred because of the rapid (10-15 days) decomposition of biuret.

Foreign research is currently studying the use of biuret for animal feed supplementation (as a source of protein in the diet). Since nitrogen is released more slowly and evenly, this reduces toxicity and generally improves the use of such preparations. Such preparations contain up to 70% biuret. Experiments show that concentrated biuret is most effective (compared to urea) in diets dominated by low-quality roughage.

Conclusion:

With modern Urea production technologies, the Biuret content does not have a negative effect on plants; therefore, dividing Urea into agricultural and industrial grades is an outdated classification. Scientific research proves the equal effectiveness for agriculture of both Urea Grade A and Grade B.

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