What are you using it on?

I sometimes use it to speed establishment of young trees. I wait until it's raining or about to rain and spread about a half cup away from trunk but under canopy. Best results for apples are at about first signs of growth. With indeterminate (all season) growers like J. plums and peaches you can do a split application with a second at the beginning of summer.

For bearing age trees, if needed, it can be applied at first growth also, but I sometimes do a very late summer or early fall application (when trees are still in leaf but terminal buds are set) instead of spring, so N is in trees at first growth. I use maybe 2 pounds per 1,000 square ft as the max for this.

General rule of thumb is that bearing peaches get equal K as N while apples get double the K. I wouldn't want to use urea alone for general maintenance fertilization of bearing trees unless I was using plenty of K rich mulch. But that would also increase N content of soil over time.

That's helpful thanks.

It's free N, so I will use it where I think I need a bit of a boost....young trees and bushes. Beds that got heavily mulched (depending how fresh the chips were) that sort of thing. Most of my usual fert application is done at this point.

I may try foliar application next spring, and I had read about trying to "stock" the tree with a mild fall application as you mentioned..

I am just used to using slower release organic sources and want to be forewarned of issues working with urea in particular.

I believe you need to buy a more expensive form for foliar application. If label doesn't suggest its use for this don't use it.

The only danger in soil application is if you apply too much because it is a salt and in excess can pull water from roots to point of killing them. I've done that when I've been careless- but to annual plants. I had some mixed with water left over from a job and just wanted to get rid of it and poured at the base of some pepper plants or something.

A little harder to kill a tree but if you are careless and use enough you can do it.

Remember to apply to moist soil and then water it in somehow. Rain is the simplest method, of course.

Rob,
Good idea not to use it as a spray on foliage unless there is a documented recommendation by University research. There are some good videos on u-tube from the U of Mass that instruct on the use of urea as a ground spray late in the fall to help break down leaf litter and fungi contained there. I use a complete type of foliar spray that contains many of the micro nutrients. A heavy dosage of urea spray(N) that shocks plants into late season growth may backfire in the spring when those tender tips are winter damaged. You are in a cold area where that could happen.

Urea for foliar spray should be low in biuret, a related chemical. I don't know whether all plants are sensitive to it but some are.