fairly well known for a long time in this "area" Urea will 'gas off' in cold wet conditions such as fall or early spring. Urea will also 'gas off' in high heat conditions with moisture. Tests have shown up to 30% off gas in 85-90 degree weather in moisture.

Best to get urea incorporated into the top soil asap in adverse conditions to hold it in the soil. In reality that's not possible with hay crops. But throughout most of growing season the off gas isn't nearly that much.

Few guys have used agratain/urea and applied in Feburary (very early spring) have not heard how those applications turned out in holding urea until the plant started growing and utilized the N.

"Here" urea is never applied in fall. Unless starting say winter wheat then maybe 30 pounds urea is applied to bump start the winter wheat. Rest of urea is applied in spring just after winter wheat has started growing again.(and spreaders can stay on top of the ground..)

.