Published on Wednesday, November 01, 2017
After a season of what felt like never ending rain, one question on everyone’s mind is, how much nitrogen (N) was lost? Will the economic optimum nitrogen rates (EONR) be higher this year? Will late season N pay more in 2017? How much did genetics play a role in our N response? We hope to address all of these questions with the data gleaned from our PFR studies.
Our Kentucky PFR site was able to start harvest on September 7, with some of the earliest harvested being N studies. Today, we are excited to share some of this data with you.
As we traditionally see in our N rate studies, the EONR was greater for the hybrid known to be a higher N user (XL® 6158AM™*brand) than the more efficient N user (XL® 5828AMX™*brand). The numbers from this year are above those from last year’s Nitrogen Rate – Corn After Soybeans study. In 2016, the greatest net return for the N efficient hybrid was at 100 units of N/A. and 150 units of N/A. for the higher N user. In 2017, we saw the greatest net return with the 175 units of N/A. and the 200 units of N./A. entries for the efficient hybrid and higher N user, respectively (shown below).
The differences we’re seeing of anywhere from 25 to 50 units of N/A. between 2016 and 2017 are not all that surprising. The 2016 season largely promoted N mineralization in soils. This year, on the other hand, was a season where the probability of N loss through leaching and volatilization were increased due to environmental conditions.
With the early-season loss many farmers experienced due to heavy early-season rain, many wondered if applying N later in the season would pay off. This year appeared to be the perfect scenario to determine when, and if, late season N would pay. However, in the case of late-season N at our Kentucky PFR site, it appeared to be too little, too late for the higher N user (XL® 6158AM™*brand). Based on the data shown below, we believe there was not enough N available early in the season during the critical ear formation period.
One additional piece of data we began collecting with our N studies in 2016 were stalk nitrate samples. Our Ohio PFR site recently took stalk nitrate samples in their Population vs. N Rate Study in 30 in. rows. The graph below demonstrates the hybrid differences with BECK 5829A4brand having more N remaining in the stalk at the end of the season as a N efficient user when compared to XL® 5665AMX™*brand as a higher N user. This trend is similar to what we noticed in 2016. We also noted that with the higher N user, (XL® 5665AMX™*brand), 190 units N./A. did not appear to be enough regardless of population in 2017.
These are the first of our PFR nitrogen results. Nitrogen studies are present across our six PFR sites. Look for these results and more in 2017 PFR Book this December!
*®XL is a registered trademark of Pioneer. XL® brand seed is distributed by Beck's Superior Hybrids, Inc.
Author: Alex Knight
Categories: PFR, PFR Reports
Tags: Nitrogen, UAN, EONR, economic optimum nitrogen rate
1/6/2018 11:44 AM
Always interesting to see n usage of different hybrids and how varied n use is at different growth stages. I would like to know if root mass and length have a correlation to n usage?
1/18/2018 1:26 PM
Hi Ron, we reached out to our director of PFR and agronomy, Jim Schwartz with your question and this was his response.
"It’s a good question, I have researched journals in the past on this very subject. What I have learned over the years is that Nitrogen (both the nitrate and ammonium form) will increase root growth and mass in the area where the nutrient is located in the soil root zone. This is known as preferential root growth. We can assume then that increased root mass and growth would likely lead to an increase in total nutrient uptake including nitrogen.
Having said that, I don’t know if anyone has established a direct genetic link between root structure and nitrogen uptake. In the past I was involved in the genetic side of the corn business and interestingly one of the smallest rooted inbreds created hybrids that became a very large portion of the genetics sold. However this inbred created some of the most nitrogen sensitive hybrids I have seen. It was notorious for being a high N user.
Long answer is that I don’t know that there is a genetic correlation however there is a link between root proliferation and the presence of nitrogen in the soil zone which then could possibly lead to increased N uptake simply from the architecture of the root system itself.
Hope that helps and thanks for the question.
- Jim Schwartz
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