In general, an application of a urea-containing nitrogen product on the surface has a higher risk of loss than if the application were incorporated or promptly irrigated into the field. Such occurrences of urea-based nitrogen loss can be further exacerbated by high temperatures and high soil pH values (generally, > 8.0); both of these factors accelerate the urease enzyme reactions responsible for ammonia volatilization loss.
As such, Adapt-N recommends the following when considering the application of a urea-containing nitrogen product:
- applications should be banded or incorporated whenever possible, as contact with the soil creates a more stable compound not subject to volatilization losses
- if urea-containing surface applications are required, higher N losses should be expected when:
- temperatures are warm;
- soil pH levels are high;
- and no means exists to rapidly dissolve the urea (either via forecasted precipitation or irrigation capabilities)
- when urea-containing surface applications are to be applied:
- a liquid product such as UAN is less subject to volatilization loss in warm conditions since the liquid material will be more rapidly drawn into the soil than a solid
- consider the use of the urease inhibitor NBPT, as this will slow the volatilization reactions in certain conditions
Adapt-N continues to enhance its modeling efforts and calibration, including efforts to simulate the specific impacts of extreme temperature and pH conditions. In the event that urea is surface applied in hot temperatures and/or high pH soils without the above suggested mitigating tactics, users are advised to expect the potential for higher than indicated losses.