urea, with a 46 percent nitrogen content, is a solid nitrogen fertilizer product. Produced from ammonia and carbon dioxide, it has the highest nitrogen content of any solid nitrogen fertilizer. Urea can be applied by itself or easily mixed with phosphate and/or potash fertilizers, often as part of a total N-P-K (nitrogen, phosphate, and potash) plant food mix. As a granular product, urea can be applied directly to the soil using conventional spreading equipment.