Liquid applications of highly available sources are most efficient and effective. Avoid working soil wet and extra secondary tillage trips. Controlled traffic pattern systems are helpful. Much less soil cracking is observed where soil mulch is present. Deep feeding roots pick up nitrogen in the nitrate form.
Plants require some nitrogen in the amine form.
The conversion of nitrate nitrogen to amine nitrogen requires energy that may not be available in a drought stressed plant. Destroy cover crops early to avoid competition for soil moisture. Consider an annual such as oats in a dry year. It will automatically winter kill.