For the past few weeks, I’ve shared nitrogen management research and producer testimonials. The producer testimonials, I felt, were especially insightful considering current input costs, commodity prices, and the focus on groundwater quality for future generations. With November 1^st a few weeks away and growers thinking about pre-plant nitrogen applications, I’d encourage you to consider the Nitrogen Challenge that I’ve shared the past few years. It is, for Pre-Plant Nitrogen applications:

• Consider applying a base rate of 50-100 lb N/ac on one field.
• Use a sensing technology like Sentinel Ag to apply the remaining nitrogen when needed based on plant needs. The technology can be used with in-season fertigation and/or side-dress applications.
• Only asking you to consider one field. Will you join us in this?

Our Extension Soil Fertility and Precision Ag Specialists wrote a series of Nitrogen management articles for CropWatch, the latest is using precision ag and sensor technology for nitrogen management, which I will share excerpts of below. Their takeaway based on research? “Applying nitrogen closer to when the crop needs it — guided by precision agriculture tools — reduces waste, increases profits and protects Nebraska’s water resources.”

“Why Precision Ag for Nitrogen? Crop sensors measure crop canopy reflectance during the season, detecting developing N stress before it is visible to the human eye. This enables farmers to adjust fertilizer applications in real time, aligning supply more closely with crop demand. Precision ag tools move nitrogen management from a “predict and apply” approach to a “monitor and respond” approach.”

Active Canopy Sensors are mounted on high-clearance applicators and emit light and measure reflectance to determine crop N status. Applications typically occur once between V8-V12 stages.

• UNL’s Project SENSE (2015–2021, >80 site-years) showed that sensor-based sidedress reduced N rates by an average of 33 lb N/acre compared to grower practices, while maintaining yields and improving profits.

Satellite-Based Sensors are passive systems that use the sun’s energy and satellite reflectance data. It’s practical today due to daily revisit times and ~30 foot resolution.

• Partnering with Sentinel Ag, Nebraska On-Farm Research (2021–2023, 24 sites) found average N savings of 56 lb N/acre with yields nearly identical to grower practice, while partial profits increased by about $24/acre.

Steps for Farmers

1. Apply a base rate: Around 50-100 lb N/ac (25% of total) at planting.
2. Set calibration: Include N reference strips or use virtual references to benchmark sensor readings.
3. Monitor the canopy: Between V8-R2 growth stages, track crop reflectance with active or passive sensors.
4. Apply as needed: Fertigate or sidedress 30-60 lb N/ac when the sensors detect developing stress. Multiple applications may be required, typically one to three per year.
5. Take advantage of irrigation systems: Center pivots with injection pumps allow timely fertigation. Ensure proper chemigation certification and backflow protection.”