Urea fertilizers are nitrogen rich organic plant and soil nutrient supplements. Pure urea contains approximately 46% nitrogen by volume and is non-toxic and pH balanced when dissolved in water. Pure urea fertilizers are available in a fine crystalline form, as granules, or as coated slow release pellets. They also lend a strong nitrogen component to solid combination fertilizers such as urea phosphate and are often used in liquid foliar feed fertilizers. Their ready solubility also makes them a popular additive in fertilizer irrigation systems.
Nitrogen is one of the staples for healthy plant grown and well balanced soil compositions and is a standard component in many fertilizers. Also known as carbamide, urea fertilizers are among the strongest sources of nitrogen, with average concentrations of 46% by volume. They are available in a number of formats, thereby making them ideal for a number of application methods. In addition to their value as a nitrogen source, urea fertilizers are also non-toxic, nonflammable, highly soluble, and neither alkaline nor acidic when suspended in water.
The most common urea fertilizer types are the crystalline and granular variants. Crystalline urea fertilizers are the finest presentations and feature the quickest release time of the dry urea applications. For this reason care, should be exercised when applying this format of the fertilizer to avoid excessive nitrogen levels. Granular urea fertilizer is coarser and takes a little longer to break down in the soil. Both types are suitable for use with mechanical spreaders and may also be employed in fertigation or combination fertilizer/irrigation systems and as a premixed foliar feed.
The other common form of urea fertilizer is the slow release pellet. This is the coarsest presentation of the fertilizer; the pellets feature a specially formulated coating that allows the release of nitrogen into the soil in a slow, controlled fashion. This permits less frequent applications and reduces the chances of plant damage resulting from over application. Their size does, however, preclude use in most mechanical spreaders, thereby making spiking the most common means of application.
Pure urea fertilizers are often used in combination with monoammonium and diammonium phosphate as a multispectrum combination. They may also be mixed with superphosphates but only if the mixture is used immediately. If allowed to stand, this particular combination will result in the urea leaching moisture from the superphosphate. This phenomenon results in a damp, coagulated mass which is difficult to store and use.