In general, urea will provide the most nitrogen at the lowest cost. It is easy to store and does not pose as a fire risk for long-term storage. Urea may be mixed with other fertilizers or may be applied on its own. For plants that love acidic soils, urea is one of the top fertilizers for acidifying soils. For gardeners who grow crops like corn, strawberries, blueberries and other heavy nitrogen feeders, urea will supply immediate and powerful applications of nitrogen.