Irrigated land should be fertilized for target yield goals. Dry conditions also bring questions concerning volatilization losses of N materials. These concerns are probably exaggerated and sometimes unwarranted. However, broadcast surface applications of granular urea are subject to rapid volatilization, especially in conservation-tillage. Under totally dry conditions or with rain or irrigation in excess of 0.5 inch, losses should be minimal.
Concerns are therefore greater in dryland.
Plowing in sidedress N may actually do more harm than good due to pruning and losing soil moisture. You can also slightly increase the sidedress N rate to compensate for loss, which may be better than pruning roots and losing soil moisture. This is thought to be from substituting ammonium bisulfite for ammonium thiosulfate as the S source. These leaves can eventually burn up entirely and fall off the plant. In the reported cases, foliar injury has been temporary and yields were essentially unaffected.