Risk and Evaluation of Nitrogen Loss
Figure 1. Illustration of factors that can influence risk of N loss.Due to being highly mobile and having a higher risk of soil loss, corn plants often experience nitrogen (N) deficiencies more often than other nutrient deficiencies. When managed properly, appropriate N levels can result in substantial potential economic returns. Limited opportunities to apply N in the fall and spring often result in re-evaluating management plans in-season. If unable to apply a preemergence N application or if N loss is suspected, there are multiple in-season options that may help minimize potential yield loss. Determining how much plant available N is readily available or still needs to be applied can be difficult to determine. Not all N applied will be readily available to the plant depending on the N form applied, the application method, the application timing and any environmental-driven N loss factors, such as temperature or precipitation.
Figure 2. Excessive spring rainfall areas in 2013 that were more prone to N loss. Source: Midwestern Regional Climate Center.Commonly Used Methods to Identify Nitrogen Needs
Late spring or pre-sidedress soil nitrate test: Soil nitrate levels increase as soil temperatures warm and mineralization rates increase. Soil nitrate mineralization peaks in late May/early June (around V5-V6) making a soil nitrate test at this time from the top 12 inches of soil a good indicator of N needs. Soil test results of >25 ppm are less likely to need additional N.
Crop sensors: Using leaf light reflectance as an indicator for additional N needs has had success. Examples of tools to use include:
N models: Modelling software such as Adapt-N utilizes soil and live weather data in combination with prior crop management practices to estimate if additional N is needed.
Application Timing and Use

N demand of corn prior to V8 is relatively low – less than 25 lbs. N/acre. With roughly 10% of the total N typically being taken up by mid-June, most early N needs of corn can be met through mineralization of soil organic matter and prior season soybean residue in corn following soybeans rotations. It is more important to ensure at least a portion of N (around 40 lbs. N/acre) is applied before or soon after planting when planting corn following corn. N demand increases dramatically after corn begins to grow rapidly at the V6-V8 growth stages making it important to have most supplemental N applied prior to this timing. By silking, plants will have absorbed near 70% of the total N needed. Yield potential can decline rapidly if N isn’t available during this critical timing. Corn continues to use significant amounts of N throughout grain fill. Split applications of N can help minimize in-season N loss and improve N use efficiency if applied timely. Split applications can provide even more value in sandy soils that are more prone to leaching and have less opportunity to mineralize N from organic matter. To maximize yield potential and enhance plant nutrient use efficiency, time N application prior to peak uptake
Nitrogen Source Considerations
Anhydrous ammonia:
One of the most inexpensive forms of N available, anhydrous ammonia can be applied late fall, early spring or sidedressed in-season. Delaying fall applications until soils begin to cool (<50° F) is important to minimize loss. Adding a nitrification inhibitor may also greatly reduce loss if excessive spring rainfall occurs as soil temperatures begin to warm. Nitrification inhibitors are not needed when sidedressing in-season, however, poor closure of knife applicators can result in ammonia loss and leaf burning.
Urea (dry):
This form of N can be broadcast pre-plant or over emerged corn with a high clearance applicator at higher speeds to cover more acres per day. Consider using a urease inhibitor to minimize volatilization loss if it is not incorporated into the soil. Timing applications of urea prior to rain events or cultivation after application can help minimize N loss. Anticipate minor leaf burn from urea trapped within the whorl of emerged corn.
UAN (liquid):
This form of N can be broadcast sprayed, fertigated, injected into the soil or dribble-applied between rows. Apply UAN as close to the timing of crop uptake as possible since a portion of it is in the nitrate form which may be rapidly lost if excess rainfall occurs. Broadcast applications can cause leaf burn, therefore, applying UAN to small corn (<V4) and at lower rates is advised unless able to sidedress. Leaf burn usually disappears quickly with good growing conditions. Sidedressing UAN to emerged corn with coulters or Y-drop applicators can reduce crop damage risk and achieve higher N use efficiency.
Product performance assumes disease presence.
© 2022 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties. Please check with your local extension service to ensure registration status. AAtrex 4L, AAtrex Nine-O, Acuron, Agri-Flex, Agri-Mek 0.15EC, Agri-Mek SC, Avicta 500FS, Avicta Complete Beans 500, Avicta Complete Corn 250, Avicta Complete Corn 500, Avicta Duo Corn, Avicta Duo 250 Corn, Avicta Duo Cotton, Avicta Duo COT202, Besiege, Bicep II Magnum, Bicep II Magnum FC, Bicep Lite II Magnum, Callisto Xtra, Cyclone SL 2.0, Denim, Endigo ZC, Endigo ZCX, Epi-Mek 0.15EC, Expert, Force, Force 3G, Force CS, Force Evo, Force 6.5G, Gramoxone SL, Gramoxone SL 2.0, Gramoxone SL 3.0, Karate with Zeon Technology, Lamcap, Lamcap II, Lamdec, Lexar, Lexar EZ, Lumax, Lumax EZ, Medal II ATZ, Minecto Pro, Proclaim, Tavium Plus VaporGrip Technology, Voliam Xpress and Warrior II with Zeon Technology are Restricted Use Pesticides.
Some seed treatment offers are separately registered products applied to the seed as a combined slurry. Always read individual product labels and treater instructions before combining and applying component products. Orondis Gold may be sold as a formulated premix or as a combination of separately registered products: Orondis Gold 200 and Orondis Gold B. Important: Always read and follow label and bag tag instructions; only those labeled as tolerant to glufosinate may be sprayed with glufosinate ammonium based herbicides. LibertyLink®, Liberty® and the Water Droplet logo are registered trademarks of BASF. GT27™ is a trademark of M.S. Technologies and BASF. HERCULEX® and the HERCULEX Shield are trademarks of Dow AgroSciences, LLC. HERCULEX Insect Protection technology by Dow AgroSciences. Under federal and local laws, only dicamba-containing herbicides registered for use on dicamba-tolerant varieties may be applied. See product labels for details and tank mix partners. Golden Harvest® and NK® Soybean varieties are protected under granted or pending U.S. variety patents and other intellectual property rights, regardless of the trait(s) within the seed. The Genuity® Roundup Ready 2 Yield® and Roundup Ready 2 Xtend® traits may be protected under numerous United States patents. It is unlawful to save soybeans containing these protected traits for planting or transfer to others for use as a planting seed. Only dicamba formulations that employ VaporGrip® Technology are approved for use with Roundup Ready 2 Xtend® soybeans. Only 2,4-D choline formulations with Colex-D® Technology are approved for use with Enlist E3® soybeans. Roundup Ready 2 Yield®, Roundup Ready 2 Xtend®, Genuity®, Genuity and Design, Genuity Icons and VaporGrip® and YieldGard VT Pro® are trademarks of, and used under license from, Monsanto Technology LLC. ENLIST E3® soybean technology is jointly developed with Dow AgroScience LLC and MS Technologies LLC. The ENLIST trait and ENLIST Weed Control System are technologies owned and developed by Dow Agrosciences LLC. ENLIST® and ENLIST E3® are trademarks of Dow AgroSciences LLC. The trademarks or service marks displayed or otherwise used herein are the property of a Syngenta Group Company. All other trademarks are the property of their respective owners. More information about Agrisure Duracade® is available at http://www.biotradestatus.com/.