Nitrogen Management



The 4Rs

Farmers want to manage their nitrogen inputs so that their crop is getting what it needs when it needs it.  The 4R System of Nutrient Stewardship allows for managing nutrients using the RIGHT SOURCE at the RIGHT RATE, at the RIGHT TIME, and in the RIGHT PLACE. This helps to minimize environmental impact, optimize harvest yield and maximize nutrient utilization, which provides a return on investment to the farmer and protection of the environment by assuring nutrient utilization by the crop to lessen the likelihood of nutrients being lost to the environment.  The framework of the 4Rs was developed by the International Plant Nutrition Institute (IPNI). 

A number of scientifically-proven nutrient management practices were discussed in the NLRS. These practices can reduce nitrogen loss by 7.5-20% per acre and phosphorus loss by 7% per acre.

Learn more about the using the 4Rs to meet the goals of the INLRS by viewing the 4R Chart (below) and the industry’s 4R Code of Practice.


Nitrification Inhibitors

Most nitrogen loss from occurs in May and June when corn is small and rainfall is abundant.  Nitrogen loss can occur from both denitrification (loss to the air) and from leaching (loss to water). 

When applied Nitrogen (N) is available for the timely demand of a growing corn crop, both returns on investment and N use efficiency are maximized.  Nitrification inhibitors help protect against negative environmental impact by slowing down the process of nitrification, which is the microbial conversion of ammonium-N (NH4) to nitrate-N (NO3).  Nitrification inhibitors extend the amount of time that applied nitrogen remains in the stable NH4 form, preventing it from leaching to water or denitrification to air. 

Nitrification inhibitors such as Nitrapyrin (known by its trade name N-Serve and Instinct) and DCD (one of the ingredients in Agrotain Plus and Super U) are most often used to stabilize N applications prior to crop uptake and can be utilized with anhydrous ammonia as well as Urea and UAN.  Benefits from using a nitrification inhibitor vary with soil type, prevailing weather and field conditions during the time of N application and crop uptake. 

Talk to your ag retailer or crop adviser about the proper selection of nitrification inhibitors, proper rate and timing of the application. 

MRTN Calculator

The Maximum Return to Nitrogen (MRTN) calculator provides a process to calculate the economic return of your N application based upon soil type as well as nitrogen and corn prices. The calculator uses recent N Rate Trial research data to determine profitable N rates. You can find the MRTN calculator here.  NREC supports on-farm N Rate Trials to continually improve the MRTN for Illinois. 

The MRTN calculator is also available as an iPhone and Android phone app, so you can take it with you wherever you go. You can download the app here.

Split Application

Splitting up your nitrogen (N) applications synchronizes your applications with your crops need and ability to utilize nutrients. Read more about optimizing nutrient management with split application here.

To better understand how split application could work on your farm, talk with your ag retailer and/or certified crop adviser (CCA).

Garry Niemeyer discusses split application


Tools for Measuring Nitrogen in-field

To find out how much nitrogen is present in your soil and to evaluate nitrogen management practices, there are many tools available in the marketplace, including:


Farmers want to know: “what is the status of the nitrogen that I have applied?” N-WATCH is a program that helps farmers understand the dynamics of nitrogen, both nitrate (N03) and ammonium (NH4), in their soil over time. Soil samples are taken from the upper foot and second foot of the soil profile. Farmers can use those results to better estimate the concentration of plant-available N as the growing season progresses.

The Illinois Fertilizer & Chemical Association has 100 sites approved for implementation in 2016 through an NREC grant.  Dr. Emerson Nafziger with the University of Illinois has provided a May and June 2016 update on N-WATCH findings at the Illinois Fertilizer and Chemical Association's website.

Individual farmers who are interested in an N-WATCH site on their farm can talk to their ag retailer and/or certified crop advisor (CCA).  FS crop specialists are another example of individuals available to implement N-WATCH sites on the farm.


N-RATE trials are another tool that helps farmers try different rates of fertilizer and learn the economically optimum rate based on end of season yield data.

The Illinois Fertilizer and Chemical Association has published the 2014 and 2015 nitrogen rate results in an interactive map. Clicking the indicators on the map will bring up the optimum N rates for trials conducted in the respective county. All the results of these trials were evaluated by the University of Illinois Dept of Crop Sciences. Dr. Nafziger at the U of I expanded upon the explanation of these N Rate trials in a UI Bulletin published yesterday which is available here.

To learn more about IFCA’s Keep it 4R Crop program, click here.

Further Information



Phosphorus loss from non-point sources tend to be associated with surface runoff and soil erosion.  Under certain conditions, leaching and subsurface flow can be significant pathways of dissolved phosphorus losses.

The INLRS focuses on practices that can reduce erosion rates to a tolerable loss (T) on acres that appear to be eroding at a higher rate.  However, the 4Rs can also help minimize phosphorus loss.  A variety of soil tests have been developed to estimate the relatively small portion of soil phosphorus that is readily available to crops. 

The IFCA 4R Code of Practice recommends soil testing for phosphorus at least once every 4 years per and following the University of Illinois recommendations for phosphorus application rates based upon the soil test results.  The University of Illinois Agronomy Handbook containing recommendations for nutrient management and application rates can be accessed here. 

Using soil tests, phosphorus fertilizers can be applied using variable rate technology (VRT), to apply the rate of phosphorus that corresponds to the soil test in the field, on 2.5 acre grids.  By adjusting application rates as the fertilizer is applied, over-application of phosphorus can be reduced as well as enhance soil fertility in areas where phosphorus levels are below optimum crop production levels. 

In addition, the 4R Code recommends that dry fertilizer (including dry fertilizers containing phosphorus) not be applied on frozen or snow covered soils in order to mitigate the likelihood of runoff or a snow melt event that can could transport the applied nutrients, including phosphorus, to streams or other bodies of water. 

To learn more about phosphorus research, watch this webinar sponsored by NREC in partnership with Illinois Farm Bureau.