Nitrogen Stewardship, Step #2: Split Applying Your Nitrogen Investment
May 30, 2017
Last month I covered the first step in Nitrogen Stewardship, Nitrogen Stabilizers. This month, I am going to cover the next step in Nitrogen Stewardship, Split Application.
While Nitrogen Stabilizers do a good job of protecting your nitrogen investment until the corn crop needs it, they cannot protect all season long. Most stabilizers have protection for 90 days in soil temps above 50 degrees. Basically, if you apply your spring anhydrous with N-Serve on March 15th and soil temps are 50 degrees and remain above that temperature, your protection will last until roughly June 15th. By June 15th, the corn crop has only used a fraction of its nitrogen needs, with roughly another 90 days to go. To get you through the second half of the growing season, your next step in your Nitrogen Stewardship plan is to delay and split apply a portion of your nitrogen needs as a side-dress application.
Below are some questions you may ask before split applying your nitrogen investment.
When does the corn crop use a majority of its nitrogen?
- As seen in the chart below, nitrogen use in the early vegetative stages is very minimal. The corn plant’s need for nitrogen steadily increases from V6 through grain fill.
- V7 – 10% of needs or 20# of nitrogen
- R1 – 60% of needs or 120# of nitrogen
- R6 – 100% of needs or 200# of nitrogen
What are the best times to split apply my nitrogen and what are my equipment options?
- As seen in the chart, the later the better. Realistically, as late your equipment will allow, plus with some room to allow for weather delays in getting the nitrogen applied. Below are some options with the pros and cons of each.
- Early Vegetative – Traditional Side-Dress and Top-Dress equipment (UAN, Urea & Anhydrous)
- Pros – Flexibility in use of products and equipment
- Cons – Nitrogen use of the corn is not at a high demand yet
- Late Vegetative – 360 Y Drop (UAN)
- Pros – Able to apply Nitrogen when the crop needs it in a very efficient manner
- Cons – Commitment on equipment
- Early Reproductive – Airplane (Urea & Slow Release Nitrogen)
- Pros – Able to apply Nitrogen when the crop needs it
- Cons – Limited to products and rate that can be applied
How do I know how much nitrogen I should apply?
- In a perfect world, you would apply the amount of nitrogen that you have saved back for split application. However, excessive rainfall or lack of rainfall can change the amount of nitrogen that is needed for a given crop. Below are two options to help you decide how much nitrogen you should apply.
- Late Spring Nitrate Test
- Soil Test right before application. Test will measure total nitrogen left and the form that it is in. Nitrogen levels in a field can be variable, the moil soil tests the better.
- Nitrogen Modeling (Climate & Adapt-N)
- Both models use historical and current weather data as well as soil types and previous nitrogen application timings. They use these variables to calculate the amount of nitrogen left in the field as well as what will be needed for the rest of the growing season.
With the combined environmental and economic benefits of split applying your nitrogen investment, it is a win-win for the environment and you the grower. Split applying nitrogen is also one of the components of our SUSTAIN platform. If you would like more information on split applying nitrogen on your farm or joining SUSTAIN, please contact your local Key Cooperative Sales Agronomist.