Urea nitrogen (urea) prilling is the most popular and most preferred representative of mineral nitrogen fertilizers, suitable for any type of soil and all kind of crops. It is a white, crystalline, organic, water-soluble fertilizer. It is acceptable and preferred especially for aqueous rice because nitrates are reduced to water and/or nitrogen (under anaerobic conditions), which nitrogen is lost in contact with air. This fertilizer is applied three times in the irrigated area - at planting , during the soil treatment and during the growth of clusters. Urea, as well as the other nitrogen fertilizers, nourishes both weeds and crops. If granules are kept dry from moisture they do not compact and could be used immediately. The advantages of this type of fertilizer are much more than its disadvantages. The urea is rapidly converted to ammonia during hydrolysis in the soil. The fertilizer does not work as fast as ammonium nitrate, as it takes several days for the food bacteria in warm and moist soil to turn the ammonium into nitrate form. Of particular importance is the time interval between the addition of the fertilizer to the soil and the possibility of the irrigation, from one side, and the temperature, from the other side, because the enzyme is less reactive at a lower than at a higher temperature /25 to 30 degrees C/.
Urea is concentrated nitrogen fertilizer with 46% nitrogen, easily soluble in water and is classified as universal fertilizer. Nitrogen actively stimulates and supports growth. If the nitrogen in the soil is insufficient, the stems remain thin and weak, they have fewer branches and begins yellowing at the lower leaves. The product should be added mainly in spring-dissolved in water or in loose and followed by copious irrigation. Compared to ammonium nitrate, urea has much better characteristics – no ability to compact, it is insensitive to the ignition and is resistant to corrosion during storage and use.