PROPERTIES OF UREA

Granular Urea(46)

All figures quoted should be considered as a typical product analysis and may vary.

PHYSICAL PROPERTIES

1.  A white granular / prilled product.
2. Particle size distribution of granular product typically ranges from 2.0 – 5.0mm.
3. Critical Relative Humidity @ 30°C: 72.5%
4. Solubility at 20°C: 108g / 100ml of water.

CHEMICAL PROPERTIES

1. 46% Nitrogen (N).
2. NH₂-CO-NH₂
3. N in the Ammine (NH₂) form and is not available for plant uptake.
4. NH₂ is converted to NH₄⁺ through the urease reaction.
5. Acidification index: 3.57 kg pure lime/kg N or 1.64 kg pure lime per kg urea applied.
6. Salt index: 75 (relative to Sodium Nitrate @ 100).
7. Biuret (NH₂-CO-NH-CO-NH₂) may be formed by polymerization at high production temperatures.

AGRONOMIC BENEFITS & CAUTIONS

1. Urea is the most widely used N source in agriculture.
2. It is the cheapest source of N and due to its higher concentration additional savings may be made on application and logistics costs.
3. Urea is readily soluble and may be put through irrigation systems.
4. Urea N is not immediately available for plant uptake.
5. NH₂ must first be converted to ammonium before it can be taken up by plants.
6. Ammonium doesn’t leach due to its positive charge.
7. Urea in solution carries no electrical charge and is prone to leaching.
8. Leached urea will lead to sub soil acidification and eutrophication of dams and rivers.
9. Urea is best washed into the soil through rainfall or irrigation or incorporated to prevent volatilization losses.
10. Application of urea to a soil surface covered with plant residue could increase volatilization due to urease in the plant residue.
11. Avoid application of urea to recently limed soil surfaces as the alkalinity from the lime could cause volatilization.
12. Urea is compatible for blending with Mono Ammonium Phosphate, Ammonium Nitrate and Potassium Chloride.
13. Avoid mixing urea with nitrates or nitrate containing mixtures to prevent NPK blend quality problems.
14. Biuret levels >1.5% may lead to toxicity especially when foliar feeding.
15. Although feed grade urea is used in animal feeds as source of non-protein nitrogen, caution should be taken to prevent spillages and contamination with drinking water as excess urea is toxic and will cause in mortality in livestock.

Please note: Consult a qualified person (Act 36 of 1947) for specific applications / recommendations.