This short article will guide you on to best use Urea as a fertilizer on land to your crops growing in soil or to your nutrient solution when growing hydroponically. 

Urea is the densest and most nitrogen dense fertilizer you can find (see comparison in Table 1 beneath). Urea has the formula CH4N2O and will in contact with water break down to ammonia (NH3) and carbon dioxide (CO2). This breakdown depends on the temperature and water content of a soil. There is hard to find exact data on this breakdown rate but Table 2 beneath should give you and indication on how long it takes.