Navigating Nitrogen Challenges in Corn

Wednesday, January 21, 2026

Tips & Tools for Smarter Management

By Mary Loggan

With fertilizer prices fluctuating, nitrogen management has become a key challenge for Ontario corn growers. Decisions about timing, rate, and placement now carry greater weight, affecting yield, profit, and sustainability.

To help producers make sense of the latest science and best practices, Better Farming recently spoke with Daniel Quinn, assistant professor of corn production agronomy at Purdue University, about how Ontario growers can refine their nitrogen programs in a changing ag landscape.

Quinn hosted a webinar in the fall for the Ontario Soil and Crop Improvement Association and the Ontario Certified Crop Advisor Association to discuss the complexities in nitrogen management in corn.

The webinar aimed to provide advisors and agronomists with practical strategies to reduce nitrogen losses, optimize application timing, and tailor nitrogen use to each field’s unique conditions. The session highlighted the challenges of managing nitrogen efficiently to support both profitable corn production and environmental stewardship.

Approach

Quinn emphasizes the importance of 4R nutrient stewardship, which remains a foundation of effective nitrogen management.

“From my perspective, I think some of the most important principles include continuing to follow the 4R principles of N management, which include the right rate, right source, right placement, and right timing and also continuing to improve, test, and use these principles specific to your environment and operation.”

Economic efficiency is also a critical factor.

“Nitrogen fertilizer is a high yearly variable cost, and it is important to use data-driven and local N rate recommendations to determine the correct rate to target.

“In addition, applying a nitrogen rate at the economic optimum rate (EONR) or the rate that maximizes economic return rather than chasing maximum yield is important, especially in a tougher economic environment,” Quinn points out.

“In most cases, there is not a linear relationship between the nitrogen rate applied and yield; therefore, you cannot always achieve higher yields just by applying more nitrogen fertilizer.

“Years of regional N-rate trials show that applying nitrogen rates substantially above the EONR provides little yield benefit, while also greatly increasing the risk of fertilizer and economic losses.”

Quinn recommends splitting applications.

“At Purdue, we recommend splitting N applications, which includes applying a smaller amount pre-plant or at-plant (e.g., starter application) and sidedressing the remainder (e.g., V4-V6 growth stage) to better match crop demand and reduce early-season loss. It is important to remember that a corn plant will only use around 20-25 lbs/acre of nitrogen up until the V6 growth stage.”

Mitigating nitrogen losses

Nitrogen is a challenging nutrient to predict and manage, Quinn says.

“Due to its behaviour (e.g., movement, availability/unavailability, performance), it is highly tied to the environmental conditions, which are becoming increasingly unpredictable.”

Wet springs and poorly drained soils pose particular challenges in Ontario.

“Excess precipitation, poorly drain-ed soils, and warm early-season temperatures can dramatically increase the potential for nitrogen losses.

“Two of the most common loss pathways are leaching of nitrate and denitrification, both of which occur when soils receive excessive rainfall and are saturated. Volatilization losses can also be substantial, particularly for surface-applied urea or UAN without incorporation, surface application on warm/moist soils, and on soils with high pH.”

Applying all nitrogen early is risky.

“These loss pathways also become more problematic when high nitrogen rates are applied early (fall or early spring) and remain vulnerable before the crop has utilized much of the nitrogen fertilizer applied.

“Splitting N applications or applying a small portion of nitrogen near planting via a pre-plant or starter application through the planter and applying the remaining total nitrogen rate in-season at early vegetative growth stages (e.g., V4-V6) can help reduce the amount of nitrogen vulnerable in the soil early in the season,” Quinn says.

Technology and management practices can help prevent losses.

“Incorporating urea and UAN within a few days of application, or applying a urease inhibitor when incorporation is not possible, helps reduce volatilization losses.

“On poorly drained soils or coarse-textured soils prone to leaching, nitrification inhibitors can help slow the conversion of ammonium to nitrate, reducing short-term leaching and denitrification risk.”

He says growers can also minimize losses by using realistic total nitrogen rates based on local or regional guidelines and their own specific location and environment.

Monitoring and adapting

Keeping tabs on nitrogen status during the season enables quick corrective actions.

“In-season monitoring is an important aspect for identifying nitrogen stress and making informed adjustments. We currently recommend that growers combine visual scouting, tissue testing, soil nitrate testing, and field history/environmental context when diagnosing potential deficiencies.

“However, none of these diagnostic methods are perfect, and it is important to use multiple to help make an informed decision.”

Quinn advises paying attention to classic signs of deficiency.

“Nitrogen deficiency symptoms can be identified by yellowing or chlorosis starting on lower leaves, a distinctive ‘V-shaped’ pattern on the leaves, and slow canopy development, which are classic signs of N stress.

“Drone or aerial imagery, particularly NDVI or similar vegetative indices, can help identify spatial variability or emerging patterns not obvious at ground level, but these areas should still be scouted at the ground level to confirm the issues occurring.”

Testing can confirm problems and guide recovery strategies.

“Tissue testing, particularly around the V5-V8 or VT-R1 stages, can confirm whether symptoms are truly related to nitrogen or other nutrient or stress interactions. Soil testing for nitrate at a depth of one to two feet can be a useful diagnostic tool, but specific considerations should be taken in the sample method and results.”

He says if deficiencies are identified early enough, sidedress N applications or high-clearance surface-banded or ‘Y-drop’ applications can be effective corrective measures.

“Previous research has shown that applications through growth stages V10-VT (tasseling) can still recover yield when deficiency is real and timely rainfall follows application.”

Looking forward

Quinn acknowledges that much remains unknown about real-time nitrogen behaviour in soil.

“Despite decades of research, several gaps remain in understanding how nitrogen behaves across diverse soils and weather conditions.

“One major gap is improving predictions of year-to-year variability in nitrogen response, especially in light of increasing rainfall intensity and the shifting climate patterns.

“Having a better handle on predicting and quantifying nitrogen movement, losses, and availability/unavailability during the season and in response to environmental conditions would drastically help to improve corn nitrogen management.”

Emerging genetics and technology hold promise, though.

“At Purdue, we are increasingly excited about opportunities related to sensor-based nitrogen management, including UAV and proximal sensing technologies, machine-learning models, and soil moisture/temperature-driven mineralization forecasts. In many cases, these technologies still have their challenges and limitations, but will only continue to get better.”

The emerging use of integrated dynamic nitrogen models that leverage real-time weather, soil, and crop data to generate adaptive recommendations represents a significant step forward.

Key takeaways for Ontario

Quinn believes Ontario producers are well-positioned to benefit from the latest nitrogen strategies if they remain data-driven and adaptable.

“For Ontario growers, I think many of the core principles can remain similar to Purdue’s recommendations for Indiana, which include prioritizing the economic optimum N rate, split applications to reduce risk, and tailoring N strategies to soil type, crop rotation, and drainage conditions.

“Ontario’s climate shares many characteristics with the eastern corn belt, such as cool springs, periods of heavy rainfall, and variable soil types, making it especially important to avoid applying all nitrogen fertilizer early when weather risks are highest,” he says.

“Split applications and in-season sidedress nitrogen applications, use of inhibitors where appropriate, and adjusting rates based on field history, local recommendations, and continued testing can help protect both yield and profitability.”

Above all, he says Ontario producers should remain adaptable and continue to monitor fields closely, use data to guide decisions, and refine rates and application methods annually based on performance and weather patterns. BF