I'm no expert, but everything I've read about soluble, chemical fertilizers is that they are very temporary in the soil, and are easily leached away by rainfall. So by my way of thinking you wouldn't use urea until the trees were ready to use it. It is surprising to me that Olive growers would fertilize during the dormant season, but they would surely know better than I. How much rain do you expect over the dormant season?

tc-

I'm only guessing here, but doesn't most the rain in Greece fall during the dormant season? Probably the only time the fertilizer can get worked down into the roots.

Up here it probably just sits there until late March. The ground will freeze up in the next month or so and until then i doubt much rainfall comes down (probably snow here)...

I'm sure there is a research paper somewhere on this topic.

I agree N is pretty mobile. However, many row crop farmers put anhydrous on in the Fall. That doesn't mean that it's the most efficient way to do it, as some N will be lost over the winter.

As Frank points out, it needs to rain to get the urea in the soil. If urea isn't watered in (by rain or irrigation) it will slowly evaporate.

I don't think any harm will come from it.

Over on the container forum, the soil expert there says it is OK to fertilize in the fall after the plant is no longer growing. Once they start to go to sleep, the fertilizer will not cause them to put on tender new growth.

I don't feed my trees after August, but I do fertilize my lawn in the fall to give it energy to get through the winter. That's standard lawn care in this area. If grass can have fertilizer in the fall, I don't see why fertilizer would harm trees.

it is entirely possible to lose surface applied urea to volatilization particularly if the soil is calcareous, pH > 6.0, windy, high humidity, moist soil on the surface and soil surface temps. of 60 deg. and above. The aforementioned factors all contribute to volatilization to a greater or lesser degree depending on the severity. In the presence of soil moisture, the urea pellets take H+ from the soil ultimately converting the urea to ammonium and then ammonia which is volatilized. Go plop some urea onto some tilled ground where you can get soil to pellet contact and watch to see if what looked like dry soil forms a small circle of wetted soil around the pellets, that's the process of urea to volatilized ammonia going on. Under ideal conditions, a very significant loss can occur in appx. 4 days. The situation is considerably worsened if the urea fails to make contact with the soil , such as laying on fallen leaves or organic mulches.

On the up side, it only takes enough rain to get the urea dissolved and down about 1/4" into the soil to insure no loss from volatilization.

The urea pellets are water soluble laying around on the ground and are therefore subject to surface waters carrying the N away especially on frozen ground if it rains.

If you plan to use Urea, get it incorporated, the sooner the better.

There is no danger for growth now. Trees disposed of all their leaves. If it were applied in October....yeah damage would possibly occur as the tempos were still kinda finicky and could have tricked the trees into growing. I fed my trees very lightly in end of august and I was worried that they would not harden off in time for this fall....but they are ok.

As for the olives, Greece and the meditterranean for the most part have mild rainy winters depending on altitude. The summers are dry and hot, very hot too sometimes 45 celcius . It is not certain that there will be rain in spring, many a times the temps start to rise in mid April till end of May with virtually no rain fall....weather is upside down the last few years. So people fertilize in winter after harvest when the rain is ample. Beneath 550 meters of altitude you will get olives trees growing in their comfort zone. UCE DAVIS from university of california has published a fertilizing schedule for olives and it describes this method I have discussed.