From the latest NDSU Crop & Pest Report:
The weather lately has made it difficult to schedule top-dress N application to the many acres of small grains/canola that were drilled in with little to no preplant N due to weather and custom applicator delays. The question now is how whether the application be scheduled before a rain, or just applied whenever it can be done. The weather is so hit or miss, that trying to schedule an application of urea right before a rain would be require astounding luck. However, if the small grains have emerged and they are tillering or later, it is important to apply the N regardless of the weather. The humidity in the mornings has been very high, and there has been sufficient dew in most of the state that small grain roots are close to the surface and the plants are self-irrigating. If the urea is treated with NBPT at the proper rate, there is no reason on these advanced small grains, or canola in the rosette stage for the N not to be applied. Corn and row crops should be side-dressed in the state by V8 so that high yield decisions are made by the corn and it is not starved for N at a time with rows on the ear and other components of yield are determined. Row-crops are best side-dressed by the use of coulter-applied UAN or anhydrous ammonia. Urea can be applied over the top, but it should be treated with NBPT and rates should be less than 60 pounds of N per acre to avoid burning in the whorl.