NITROMAX
Maximizing Economic Returns on Nitrogen Fertilizer
Gene Stevens, Ray Massey and David Dunn
University of Missouri - Commercial Agriculture Program and Extension/Outreach
About NITROMAX
NITROMAX is a program designed to help farmers apply the most profitable rate of nitrogen fertilizer on crops. Response curves in the program are used to predict crop yields at different nitrogen rates. These curves were derived from fertility research on corn, cotton, and rice. In the program, quadratic equations are used to mathematically describe the response curves. Users select a response curve and enter crop price, and fertilizer price. The program calculates the maximum crop yield and its corresponding nitrogen rate. Then the rate of nitrogen is reduced 1 pound per acre. If the value of the yield loss from the reduced N is less than the price of 1 pound of N, another pound of N is reduced. This continues in 1 pound increments until the value of the crop yield loss equals or exceeds the price of the 1 pound of nitrogen. This is the most profitable N rate. In most crops, the most profitable N rate is 90 to 98% of the maximum yield.
Currently, there are two ways to use NITROMAX, a web based version and a downloadable Microsoft Excel spreadsheet. There is no difference in the results of these two versions. However, the results from the Excel spreadsheet will be faster and therefore easier to see how different inputs affect the maximum nitrogen rate. The Excel spreadsheet also allows the user to select between different units (U.S. Standard or Metric units). Instructions on how to use each version follow.
Microsoft Excel Version Instructions
In the upper right corner of the sheet 'Enter Crop', click the preferred option for results to be displayed (U.S. Standard or Metric units). Next, select the desired crop (corn, cotton, or rice). Select the desired nitrogen fertilizer by clicking on the appropriate option button at the top of the screen. Use the spin buttons to enter fertilizer prices and nitrogen prices. View response curves by clicking on each one in the dialogue box. The location and date of the field research for each curve is shown in the box. When a curve is selected, the soil type and its maximum yield are shown with the corresponding nitrogen rate. The name of the scientist(s) who contributed the curve is also displayed. Study the effect that soil, location, and year-to-year weather has on crop response to nitrogen by selecting several curves one at a time. The spreadsheet can be downloaded here.
Web Interactive Version Instructions
The input and outputs are divided into two frames. The top frame is where the user inputs all information. The bottom frame is where the results are posted. The top frame or input portion is divided into three sections: fertilizer, crop, and response curve.
Fertilizer Section:
First, select the type of fertilizer used from the drop box. Next, change
the price of the fertilizer selected using the plus and minus buttons.
Crop Section:
Select the type
of crop needed (corn, cotton, or rice) and change the price of the crop using the plus
and minus buttons.
Response Curve Section:
Select the type of response curve needed for that crop. Several locations
are available depending on the crop selected.
Click 'Update Results' to view the new output in the bottom frame. The output should include the most profitable nitrogen rate (with and without interest), the maximum yield nitrogen rate, the maximum grain yield, and the percent max yield. The name of the scientist(s) who contributed the curve is also displayed. To see how different inputs affect nitrogen rates, two graphs are included. One graph represents the percent max yield and the other is a response curve. Study the effect that soil, location, and year-to-year weather has on crop response to nitrogen by selecting several curves one at a time. The web interactive version is available here.
General Information
When crop price is high and N fertilizer price is low, the most profitable N rate is closest to maximum yield. Interest usually has a minor role in the calculations of most profitable N rate. Interest should be entered on annual rate, but calculations are based on borrowing the money for six months. If a farmer desires a greater return on his dollar than the current interest rate, inflate the interest rate accordingly.
Currently all of the response curves in the program are from Missouri. Agronomists from other locations are invited to submit quadratic equations from their research by e-mail. In the future, we hope to have enough curves to cover other crops and most soils and climate conditions. All contributors will be recognized on the screen when their curve is clicked.