• Nitrogen applications should correspond to crop needs whether applied as a single or a split application.
• In modern corn genetics, nitrogen needs post tassel are ≥30%.
• Protecting this expensive input against loss is an important part of increasing crop uptake, decreasing environmental loss and practicing 4R Nutrient Stewardship.
• NBPT urease inhibitor products are applied to limit the loss of ammonia gas to the atmosphere, also known as volatility.
• Different NBPT products exist and they differ in the percentage of active ingredient per gallon and therefore the rate applied per ton of nitrogen.

With little nitrogen applied in the fall of 2018 and a rough, wet start to planting this spring, questions have come up regarding nitrogen form, application timing and the use of nitrogen stabilizers.  Regardless of what form of nitrogen you decide to apply, the growing crop really has no preference; a pound of nitrogen is a pound of nitrogen.  More importance should be given to the timing of N application as it relates to crop needs and the use of a N-stabilizer to protect the high cost of this investment. 

Dr. Emerson Nafziger, Professor Emeritus at the University of Illinois, recently stated in a summary of nitrogen research for 2018 that “The main lesson we’ve learned from our N timing and N form studies over the past five years is that corn plants need to have a substantial amount of N available in the soil near the row after plants emerge and before their nodal (main) root system starts to develop.”  The first set of nodal roots becomes visible at corn stage V2.  While Nafziger doesn’t state how much nitrogen is “significant”, this study involved treatments where 100% N was applied prior to or at planting, or the total N was split in two applications and 2/3’s were applied prior to or at planting, followed by 1/3 post planting.  The second treatment timing (2/3’s followed by 1/3) found no yield difference with the second application of nitrogen all the way up to tassel time.  As seen in Fig. 1 below, nitrogen uptake patterns in modern hybrid genetics show corn nitrogen needs of ≥30% post tassel. Therefore, it is important to ensure that nitrogen is there for crop uptake post tassel, regardless of the form applied.

Figure 1. Total Maize N uptake and partitioning across four plant stover fractions: leaf, stalk, reproductive and grain tissues. Each value is a mean of six hybrids across two site years at Urbana, IL (2010) and DeKalb, IL (2010). (Source: “Modern Corn Hybrids’ Nutrient Uptake Patterns” R. Bender, J. Haegele, M. Ruffo & F Below. 2013).

It also has become increasingly important to practice the 4R’s of Nutrient Stewardship as public pressure for accountability to limit nitrogen loss to the environment intensifies.  When surface applying UAN or urea, stewardship, in addition to nitrogen use efficiency (NUE) may require the use of an NBPT containing product to limit the loss of ammonia gas to the atmosphere (volatility).  NBPT protects surface applied UAN (Y-drop, dribble, broadcast) or urea (broadcast) from volatilization.  Differences exist among commercial products in the percent of active ingredient (AI), NBPT and rate applied per ton of urea or UAN.  Even with these differences, the net amount of AI applied per ton is relatively the same making it important to pay attention to the cost of product per ton and differences in the handling of the product. For example, Agrotain® Advanced from Koch™ Agronomic Services has 30% NBPT.  Koch also has introduced ANVOL™, (16% NBPT), a new longer chained chemical form of NBPT that is designed to extend protection over other products on the market.  Products such as SuperU® urea from Koch include NBPT (for control of volatilization) and DCD (for suppressing nitrification) in their formulation.  With nearly 80% of a corn root system residing in the top foot of soil, keeping the applied N in that top root zone helps improve NUE thus limiting environmental impact.  Other effective products on the market that also help with nitrogen leaching and denitrification (loss of N gas to the atmosphere under saturated soil conditions) include several products containing nitrapyrin. Products like N-Serve® and Instinct® II from Corteva™ have long histories of use and proven track records.  Also available from Koch is Centuro™ which also protects against leaching and denitrification. For more information on N fertilization, timings, stabilizers and rates contact your local FS crop specialist. 

All third party trademarks contained herein are the intellectual property of their respective owners.