I suggest IBDU slow-release granules (or maybe methylene urea). Slow-release and organic nitrogen sources stay in the top layer of the soil and the nitrogen releases as it rains, (or irrigation)(sometimes bacterial action). Continuous slow feeding. Go easy on the irrigation to be sure; do not drive the nutrients through the soil and into the deeper layers. Sandy, highly leachable soil needs 75 percent of nitrogen in the slow-release form.
I could be wrong--but I do not think urea can be absorbed by leaves until it is broken down to nitrates.