Improving nutrient management on farms is a critical issue nationwide. Applying a portion of N fertilizer during the growing season, alongside the growing corn crop is one way to improve nitrogen management. Sidedress N applications allow the availability of N fertilizer to more closely match the time when the crop is rapidly uptaking N. Additionally, waiting to apply a portion of the N during the growing season allows for management which is responsive to current growing season conditions.

Crop canopy sensors have been used during the growing season to direct in-season N application and have been found to reduce N application and increase profit. This sensor technology is most commonly used on high clearance applicators, where sensing and application take place simultaneously.

In extreme southeast Nebraska where this project is located, in-season N application by ground-based applicators is not common due to rolling hills, contour, and terrace farming. Many farmers in this area are trying aerial N applications, and more recently, variable-rate aerial N applications. The availability of small passive, multi-spectral sensors which can be carried on a drone allows the possibility of crop canopy sensing an N application from aerial platforms, eliminating the need to drive through the field and damage the crop. 

The goal of this research project is to evaluate the use of a passive crop canopy sensor to direct variable-rate, in-season N fertilizer recommendation rates on corn and apply this recommendation using variable-rate aerial technology.

The farmer’s traditional N management was compared to two different sensor approaches: 84 kg ha-1 N applied as a base rate plus in-season application and 112 kg ha-1 N applied as a base rate plus in-season application. Weekly aerial imagery and sensor data was collected. Yield response and profitability for the farmer’s traditional method and the drone based methods will be compared on a per strip basis and spatially, on a sub-strip basis.