Urea is a cheaper source of nitrogen, but the nitrogen can be completely lost under conditions favoring volatilization. Volatilization losses from urea-based fertilizers are reduced by application to dry surfaces. It is best to apply urea fertilizers just before a minimum of one-half-inch rainfall so the nitrogen is washed into the soil. In a 1997 study of nitrogen sources, 40% of the urea was lost in only five days before rainfall was received. do not use urea if the pasture has been surface limed within the past three months. Liquid nitrogen solution (28%) is usually made up of urea and ammonium nitrate, so only the urea portion is subject to volatilization losses.