Nitrogen Fertilizer -Urea


Importance of the Fertilizer Urea is a white, crystalline, organic chemical produced in granular or pellet form. It contains 46 per cent nitrogen. It is highly soluble in water and, therefore, subject to rapid leaching. It is, however, quick-acting. When applied to the soil, its nitrogen is rapidly changed into ammonia and absorbed by the plant.
Amount of Available Nutrients Urea contains 46 % Nitrogen.
Compatibility in fertilizer mixtures Urea may be mixed only prior to application with Murate of Potash, Potassium Sulphate, Ammonium sulphate, Calcium Ammonium Nitrate, Sodium Nitrate, Super phosphate, Ammonium phosphate and Calcium carbonate.
Reaction of the Fertilizer in Soil Soil microbes convert amide form of Nitrogen which is not available to plant to ammoniacal and nitrate form which is available to plant. In soils rich in humus urea makes hydrogen bond with humus like substance. In acid soils urea may react with nitrous acid to form nitrogen gas. Urea may decomposed by urease enzyme to form ammonium carbonate which is oxidized to nitrous acid which in turn oxidized to nitric acid. Ammonium carbonate may be decomposed to liberate ammonia. Ammonium ions may be absorbed in the clay colloids. Ammonium and nitrate may also be utilized by the micro organism or in alkaline soils volatilization loss occurs as ammonia.
Situations where Recommended Urea is recommended in all types of soil except in light paddy soils with possible leaching losses. Urea is used in submerged rice soil conditions. It may be applied in sowing time or as top dressing. But it should not be allowed to come in contact with seed.
References 1. Yawalkar, K. S., Agarwal, J. P., and Bokde, S., (1996) Manures and Fertilizers, Agri-Horticultural Publishing House, Nagpur