Variable Rate Nitrogen Applications

Supporting the Right Rate and Right Place

Precision technologies apply more nitrogen where crops can use it, and less where they can’t — improving efficiency and protecting the environment.

What It Is

Variable Rate Nitrogen (VR-N) adapts fertilizer applications to the unique conditions within each field. Using precision ag tools like yield maps, soil sampling, or crop sensors, farmers can apply nutrients only where and when they are needed most.

What to Expect

Improved nitrogen efficiency → Match fertilizer applications with crop demand across different field zones.
Whole-system approach → Incorporate all 4Rs when designing VR-N strategies, factoring in spatial variability and in-season conditions.
Technical support needed → VR-N requires managing data, compatibility issues, and creating field-specific recommendations, often with the help of trusted advisors or service providers.

Proven Benefits

On Virginia’s Eastern Shore, VR-N in wheat saved farmers an average of 4 lbs N/acre (7% of spring application).
Corn sidedress applications were reduced by 21 lbs N/acre while maintaining yields (Thomason et al., 2011).
NDVI drone imagery helped identify zones with residual nitrogen from previous crops, reducing unnecessary applications.

In the Field

In 2017, the Delaware-Maryland 4R Alliance partnered with Hoober, Inc. and local farmers to test UAV (drone)-based NDVI mapping for corn sidedress. The imagery revealed areas with higher residual soil nitrogen, which would have been missed if only using yield history or soil type. This allowed for more precise applications and reduced overall nitrogen use.

Getting Started

Assess whether your fields have significant yield or soil variability.
Work with an advisor or crop service provider to integrate precision tools like crop sensors or UAV imagery.
Start small — trial VR-N on select acres to see ROI before scaling up.