Optimal Timing for Urea Application

The exact timing for applying urea fertilizer depends on specific environmental and soil conditions to maximize its effectiveness and minimize nitrogen loss.

Urea fertilizer should be applied:

• On sod crops when the atmosphere temperature is below 60 degrees Fahrenheit.
• When broadcasting on soils with a high pH (above 7.5), the material should be incorporated into the soil as soon as possible.

Effective urea application hinges on understanding how urea interacts with different conditions. Urea is susceptible to volatilization (loss as ammonia gas) if not managed correctly, especially in warm temperatures or on high pH soils when left on the surface.

Temperature Considerations for Sod Crops

For sod crops, applying urea when the atmosphere temperature is below 60 degrees Fahrenheit helps to reduce the risk of nitrogen loss through volatilization. Cooler temperatures slow down the activity of the urease enzyme, which breaks down urea into ammonia, thereby allowing more time for the urea to be incorporated into the soil by rain or irrigation, or to diffuse into the soil solution.

Soil pH and Incorporation for Broadcast Applications

When urea is broadcast onto the soil surface, particularly on soils with a high pH (above 7.5), it is crucial to incorporate the material into the soil as soon as possible. High pH conditions accelerate the conversion of urea to ammonia gas by the urease enzyme, leading to significant nitrogen losses if the urea remains on the surface. Incorporation can be achieved through:

• Tillage: Physically mixing the fertilizer into the soil.
• Irrigation: Applying water immediately after application to dissolve and move the urea into the soil profile.
• Rainfall: Relying on natural precipitation shortly after application.

This immediate incorporation helps to move the urea away from the soil surface where volatilization is most likely to occur, allowing it to be absorbed by the soil and made available to plants.

Summary of Application Conditions

To summarize the key conditions for urea application:

For further detailed information on fertilizer urea, refer to the University of Minnesota Extension.