Improving nutrient management on farms is a critical issue nationwide. This project seeks to reduce over-application of nitrogen, reduce environmental contamination, and provide economic benefit for farmers due to more precise nitrogen management.
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. For example, higher than expected mineralization may result in more N being available to the crop. By waiting to apply a portion of the N during the growing season, farmers can be reactive to this decreased N fertilizer need and reduce applications accordingly. Conversely, heavy rainfall may lead to denitrification or leaching of N. By not applying all the fertilizer upfront, less N is lost and additional N fertilizer can be supplied to meet crop demand. Additionally, variable-rate N fertilizer applications have the ability to direct N applications according to spatial variations in the field, further improving N use efficiency.
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. The sensor will measure light reflected off the crop canopy from specific wavebands which can be used to calculate a normalized difference red edge index (NDRE) which is a means of determining the N status of the crop. Compact, lightweight sensors have been produced, allowing them to be attached to an unmanned aerial vehicle (UAV) to rapidly and frequently monitor crop NDRE.
The Research Project
The randomized, replicated on-farm research experiment will have three treatments:
1) traditional: static-rate, pre-plant N application at a rate normally used
2) 75 lb/acre base rate + sensor-based in-season N: 75 lb/acre N will be applied prior to planting as anhydrous ammonia. A sensor on a UAV will determine crop NDRE throughout the growing season. A variable-rate application of N will be made when a critical level is reached using an algorithm to determine the N rate. Variable rate N will be applied aerially as dry Urea.
3) 100 lb/acre base rate + sensor-based in-season N: Same as the sensor+algorithm, but with a 100 lb/acre base rate.
In the map shown on this page, anhydrous ammonia base rates were applied in February 2017 according to a prescription.