To make urea, fertilizer producers combine ammonia with carbon dioxide (CO2), but when farmers apply that urea to the soil, an equal amount of CO2 is emitted to the atmosphere. No CO2 is permanently stored or sequestered through the production of urea.
This is a statement of the obvious, I'm told, but it's worth stating for three reasons. First, not everyone knows it. Second, there was zero data in the academic literature supporting the fact, until now (see below). And third, next generation ammonia-urea plants with "zero-emissions" are becoming a reality, despite some of these new technologies relying on fossil fuel feedstocks.