You may have read in some of my previous writing that urea is okay to use in small quantities. It is true that in very small amounts, the microbes eat it functions fairly well to build soil health. On the other hand, when used at the rates recommend by the toxic chemical pushers, there is far too much nitrogen for the microbes to use. Much of it is volatized adding to air pollution, and a large amount of it runs off and leaches through the soil and into the water stream. Therefore, the way it is commonly used is detrimental to the air, the soil and the water. Even the part that gets into the plants tends to build weak watery cells and that condition invites pests and disease pathogens.
Even though it is the only synthetic fertilizer that contains some carbon, it is still nowhere near a "balanced" fertilizer. The worst urea product of all is the A & M and toxic talk show recommended (and pedaled) 24 - 0 - 0.
Urea: Urea is a synthetic protein and is the best choice of all the synthetic fertilizers. Microbes accept urea the same as they do urine. It contains 45 percent nitrogen. Natural urea is a waste product from animals. Synthetic urea is the only manmade fertilizer that contains carbon. However, sugar or molasses and humic acid needs to be applied with it to maximize its efficiency. It is made synthetically by reacting ammonia and carbon dioxide under high pressure and temperature. Urea, when used at low levels and in conjunction with organic matter and sugar, is an effective and organically acceptable fertilizer. It helps jump start the microbes. Humates are a good organic matter choice for this use. Large amounts of urea can damage seeds and vegetation can be toxic to aquatic life because of ammonia buildup.