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Nitrogen Rate and Timing Studies

Many farmers are interested in finding ways to grow the same or more bushels with less inputs. Nebraska On-Farm Research has been working with farmers to test different studies, including nutrient management ones, on their farms since the 1990’s. Area on-farm research cooperators and I started the 2022 season with 35 studies, but only 15 made it to harvest with the hail.

While there’s numerous nutrient management studies throughout Nebraska, I’ll focus on local data. Since 2020, one farmer in the Henderson area has been testing nitrogen rate and timing studies. Fields were impacted by July 9 windstorms in 2020 and 2021 and the June 14 hailstorms in 2022. His goals include testing any benefits (yield and nitrogen carryover) to split applying nitrogen vs. applying it mostly up front, and also testing his nitrogen rate vs. +/- 50 lb N/ac. He’s currently amassed 7 site-years worth of data of which only 3 have shown a difference when reducing his grower rate by 50 lb N/ac. For reference, the soil type is silty clay loam/silt loams and his yield goal is around 240 bu/ac. These studies received partial sponsorship from the Upper Big Blue NRD. All the data is shown in charts at jenreesources.com.

In 2022, his nitrogen timing study was conducted on the same strips as in 2021. This study looked at spring vs. split application of nitrogen at 50 lb rate differences. Treatments were: Spring anhydrous of 180 lb N/ac, Spring anhydrous of 230 lb N/ac, Split 180 (120 lb N as spring anhydrous + 60 lb 32% UAN sidedress), and Split 230 (170 lb N as spring anhydrous + 60 lb as 32% UAN sidedress). The field received 35% hail damage at V5 with harvest stands reduced to around 23,000 plants/ac. Yields from the four treatments listed above respectively: 226, 229, 227, and 230 bu/ac with no yield differences amongst the treatments. In 2021, on the same strips of spring vs. split, treatments of 140 vs. 190 lb N/ac were compared. There again were no yield differences with yields ranging from 235-237 in 2021.

In 2022, he also conducted a study testing the economically optimum nitrogen rate on irrigated corn. The previous crop was soybean and this field had 25% hail damage at V6 on June 14, reducing harvest stands to an average of 23,500 plants/ac. Fall anhydrous in November 2021 was applied at rates of 0, 50, 100, 150, and 200 lb N/ac. All treatments then received a sidedress application of 50 lb N/ac as 32% UAN at V8. The sidedress was surface applied and didn’t get incorporated until a rain 10 days later. 2022 was a high mineralization year, but it’s still incredible to see that with only 50 lb N/ac, he achieved 211 bu/ac! The 100 lb N/ac received 222 bu/ac. There were no yield differences between the 150, 200, 250 lb N/ac treatments with respective yields of 231, 232, and 230 bu/ac. The economically optimal nitrogen rate was determined to be 121 lb N/ac for this field. Studies like this are interesting to show what our farmers are trying. They’re also helpful for examining and rethinking nutrient application rates and timing to our fields. If you’re interested in learning more, would encourage you to RSVP for our on-farm research update held Feb. 15 at the Holthus Convention Center in York at: RSVP: https://go.unl.edu/2023ofr.

Hamilton Co. Ag Day: Steve Melvin has put together great opportunities for the Hamilton and Merrick Co. Ag Days this year! Jan. 31 is Hamilton Co. Ag Day at Fairgrounds in Aurora with registration at 9 a.m. and program beginning at 9:30 a.m. with Corn and USDA updates. Additional morning topics include corn and soybean insect and disease updates and irrigation scheduling info. Lunch is sponsored by AKRS equipment. The afternoon is focused on a Farm/Ranch Transition Succession Workshop with Al Vyhnalek, UNL Farm succession specialist and Tom Fehringer, Attorney. I’ve heard a lot of farm succession speakers and this duo of Al and Tom is extra helpful. They are so practical and share in a way that is easily understandable and relatable. I could relate to the family stories they shared and have seen some people in tears for two main reasons: wishing they had heard the info. earlier and also grateful they had the info. now to change things for the future. Please consider attending!


2020 York County Spring Anhydrous Nitrogen Rate on Corn
This study essentially showed what the previous studies had: that less nitrogen can be applied without hurting yield or net return. 50 lb/ac N above the grower rate resulted in reduced profit. Field yields were impacted by the July 9, 2020 wind storm. This study is sponsored in part by the UBBNRD.

Pre-PlantIn-seasonlbs N/bu grainYieldMarginal Net Return
110 lb N/ac spring NH3 (March)25 lb N/ac as UAN May0.73 C184 A$599.14 A
160 lb N/ac spring NH3 (March)25 lb N/ac as UAN May0.98 B189 A$600.38 A
210 lb N/ac spring NH3 (March)25 lb N/ac as UAN May1.23 A191 A$594.88 A
*Values with the same letter are not statistically different at a 90% confidence level. Marginal net return based on $3.51/bu corn, $8/ac for the anhydrous application cost, $0.28/lb N as anhydrous, and $0.35/lb N as UAN. 

2020 Hamilton County Evaluating Nitrogen Rate and Timing on Corn
This study showed no difference in nitrogen timing nor rate on yield and showed less nitrogen can be applied without impacting yield. Yields were impacted by the July 9, 2020 windstorm. This study is sponsored in part by the UBBNRD.

Pre-PlantIn-seasonlbs N/bu grainYieldMarginal Net Return
180 lb N/ac Fall NH325 lb N/ac as UAN May1.03 B199 A$629.85 A
230 lb N/ac Fall NH325 lb N/ac as UAN May1.27 A201 A$625.49 A
180 lb N/ac Spring NH325 lb N/ac as UAN May1.02 B201 A$638.30 A
230 lb N/ac Spring NH325 lb N/ac as UAN May1.24 A206 A$641.70 A
120 lb/ac N Spring NH325 lb N/ac as UAN May
60 lb N/ac side-dress V8
1.00 B205 A$645.69 A
170 lb/ac N Spring NH325 lb N/ac as UAN May
60 lb N/ac side-dress V8
1.24 A206 A$633.50 A
Values with the same letter are not significantly different at a 90% confidence level. Marginal net return based on $3.51 bu corn, $0.28/lb N as anhydrous ammonia, $8.00/ac for anhydrous application, $0.35/lb for UAN applied with herbicide or as a sidedress, and $3/ac for sidedress UAN application.

2021 Hamilton County Spring Anhydrous N Rate Study
This study showed no reduction in yield of grower rate vs. 50 lb N/ac under the rate; however, the yield from the -50 lb rate treatment was different from the 50+ rate. There were no differences in marginal net return. This field received 20% wind damage from July 9, 2021 storm. Partially sponsored by UBBNRD.


2021 York County Spring Anhydrous N Rate Study
This study showed no yield difference between the grower rate and 50 lb N/ac over the grower rate but they yielded significantly more than the 50 lb N/ac under treatment and had greater marginal net return. This field received 20% wind damage from July 9, 2021 storm. Study partially sponsored by UBBNRD.


2021 York County Timing by N Rate Study
(Sponsored in part by UBBNRD)

Spring 140 lb/ac: 110 lb/ac N as anhydrous and 30 lb/ac N with herbicide
Spring 190 lb/ac: 160 lb/ac N as anhydrous and 30 lb/ac N with herbicide
Split 140 lb/ac: 50 lb/ac N as anhydrous, 30 lb/ac N with herbicide, and 60 lb/ac N sidedressed at V8
Split 190 lb/ac: 100 lb/ac N as anhydrous, 30 lb/ac N with herbicide, and 60 lb/ac N sidedressed at V8

2022 York County Timing by N Rate Study (same strips as 2021)
(Sponsored in part by UBBNRD)
35% hail damage on June 14, 2022 at V5

Spring 180 lb/ac: 180 lb/ac N as anhydrous
Spring 230 lb/ac: 160 lb/ac N as anhydrous and 30 lb/ac N with herbicide
Split 180 lb/ac: 120 lb/ac N as anhydrous and 60 lb/ac N sidedressed at V8
Split 230 lb/ac: 170 lb/ac N as anhydrous and 60 lb/ac N sidedressed at V8


2022 Economically Optimum Nitrogen Rate
(Sponsored in part by UBBNRD)
25% hail damage on June 14, 2022 at V6

Treatments: Fall anhydrous applied November 2021. Sidedress application of 50 lb N/ac 32% UAN at V8.
50 lb N/ac (0 lb anhydrous, 50 lb sidedress)
100 lb N/ac (50 lb anhydrous, 50 lb sidedress)
150 lb N/ac (100 lb anhydrous, 50 lb sidedress)
200 lb N/ac (150 lb anhydrous, 50 lb sidedress)
250 lb N/ac (200 lb anhydrous, 50 lb sidedress)

Economically optimum nitrogen rate was determined to be 121 lb N/ac based on a corn price of $6.57/bu and nitrogen price of $0.98/lb.


JenREESources 11/8/21

Nitrates and Grazing Forages: the fact that we haven’t had a hard frost is throwing a wrench into grazing covers. For those with cattle on cover crops, please be aware of the potential for nitrate and/or prussic acid poisoning with the light frosts. Nitrogen moves from the roots up the plant. When a frost occurs, nitrates accumulate in the plant, and, we had lighter frosts for several days in a row. For sorghum species where prussic acid poisoning is also of concern, we say to wait at least 5 days before returning animals back to the field after frost. And, for every light frost, the 5 day window resets until a hard freeze occurs (at 26F or lower). It’s been hard to find any recommendations regarding nitrate accumulations in brassicas after frost…and what happens to the nitrates after a frost. We know weathering in general reduces nitrate levels in plants by spring. Just advising to watch cattle with these light frosts-especially those in seed corn fields that had milo in corners.

A study conducted by Mary Lenz, grad student for Dr. Mary Drewnoski, found brassicas accumulate more nitrate than small grains, millet, sorghum/sudan grasses, or cover crop mixes, and that 48% of the brassica samples submitted to Ward Labs were considered “highly toxic” for nitrate levels compared to 20-28% of other cover crop species. Yet what’s interesting is how often fields in the “highly toxic” level (or with no testing) are grazed with no impacts. Dr. Mary Drewnoski has shared that brassicas and immature grasses are also high in energy and that cattle consuming diets high in energy can handle more nitrates. So, this may be why we thankfully don’t see more issues grazing turnips and radishes high in nitrate. She shared other factors for consideration are that cattle are selective and will graze the upper-most parts of plants first which are lower in nitrates, grazing animals eat more gradually than those receiving hay, and the high moisture forages that are grazed release nitrates at a slower rate than with dry forages like hay. Ways to reduce nitrate concerns when grazing include: turning out cattle full before grazing the covers, using lower risk cattle such as open cows and stockers (as pregnant cows have risk of abortion when fed forages high in nitrate), graze lowest nitrate fields first for adaptation, graze highest nitrate concentration fields lighter so not as much forage is removed, or there’s also the option of not grazing fields that are very high in nitrates.

Corn Nitrogen Calculator: For those desirous to calculate N rates utilizing different sources and prices, the UNL nitrogen calculator has been updated. Before, it didn’t allow for the prices we currently are experiencing and there’s been some updates to the manure credits. The UNL nitrogen equation itself has remained the same, and honestly, I still say it’s conservative. For example, the nitrogen credit from soybeans is 45 lbs/ac in the equation. However, on-farm research conducted in the mid-2000’s in this part of the State found a credit of 1 lb for every bushel up to 60 bu/ac was achievable in irrigated soybean.

To utilize the N calculator, go to: https://cropwatch.unl.edu/soils, scroll down to “Corn Nitrogen Recommendations Calculator” and download the excel spreadsheet. You will want to open the “October 2021” version. They’re currently working on an online calculator for the future.

A few questions I received this week: “How much yield loss should I expect if I reduce N rates?” and “With higher corn prices, how much profit is one giving up with lower yields due to lower N application?”. These are valid questions and ones every operation will have to determine for oneself. That’s where on-farm research is really helpful too.

We have lots of data through the years of comparing a grower base rate +/- 30 lbs. of nitrogen mostly showing no yield differences. Most of this data is from the 1990’s for this part of the State, with data from the past 10 years from other parts of the State. In 2020 and 2021, a grower conducted nitrogen rate studies in York and Hamilton counties using his rate +/- 50 lb N. As I’ve shared the results with growers with the above-mentioned questions, they’ve been surprised at the yields and profits. I’ve summarized the grower’s results at jenreesources.com and also showed the profit based on today’s fertilizer prices. There’s a few ways to approach this data. It shows minimal benefit to yield and profit for increasing nitrogen application above the grower’s rate. Thus, there may be opportunity this year for those who have been over-fertilizing for high yield goals to try cutting back. It also shows that yield is reduced to some extent by reducing N rate 50 lb/ac below what the grower’s rate typically would be; however, with today’s prices, profit may be comparable. We also have several farmers who are already doing a great job with fertilizer rate for their realistic yield goals, so there may not be room to cut back. Appreciate all the farmers conducting on-farm research so we have data to share to help in answering questions!


*Please overlook my formatting issues below. There are no links even though some of the wording keeps appearing in blue instead of black.

2020 York County Spring Anhydrous Nitrogen Rate on Corn
This study essentially showed what the previous studies had: that less nitrogen can be applied without hurting yield or net return. 50 lb/ac N above the grower rate resulted in reduced profit. Field yields were impacted by the July 9, 2020 wind storm. This study is sponsored in part by the UBBNRD.

Pre-PlantIn-seasonlbs N/bu grainYieldMarginal Net Return
110 lb N/ac spring NH3 (March)25 lb N/ac as UAN May0.73 C184 A$599.14 A ($849.30)
160 lb N/ac spring NH3 (March)25 lb N/ac as UAN May0.98 B189 A$600.38 A ($837.80)
210 lb N/ac spring NH3 (March)25 lb N/ac as UAN May1.23 A191 A$594.88 A ($810.70)

*Values with the same letter are not statistically different at a 90% confidence level. Marginal net return based on $3.51/bu corn, $8/ac for the anhydrous application cost, $0.28/lb N as anhydrous, and $0.35/lb N as UAN. (Updated marginal net return using $5.20/bu corn, $0.75/lb N as anhydrous and $1/lb N as UAN.)


2020 Hamilton County Evaluating Nitrogen Rate and Timing on Corn
This study showed no difference in nitrogen timing nor rate on yield and showed less nitrogen can be applied without impacting yield. Yields were impacted by the July 9, 2020 windstorm. This study is sponsored in part by the UBBNRD.

Pre-PlantIn-seasonlbs N/bu grainYieldMarginal Net Return
180 lb N/ac Fall NH325 lb N/ac as UAN May1.03 B199 A$629.85 A ($866.80)
230 lb N/ac Fall NH325 lb N/ac as UAN May1.27 A201 A$625.49 A ($839.70)
180 lb N/ac Spring NH325 lb N/ac as UAN May1.02 B201 A$638.30 A ($877.20)
230 lb N/ac Spring NH325 lb N/ac as UAN May1.24 A206 A$641.70 A ($865.70)
120 lb/ac N Spring NH325 lb N/ac as UAN May
60 lb N/ac side-dress V8
1.00 B205 A$645.69 A ($880.00)
170 lb/ac N Spring NH325 lb N/ac as UAN May
60 lb N/ac side-dress V8
1.24 A206 A$633.50 A ($847.70)

Values with the same letter are not significantly different at a 90% confidence level. Marginal net return based on $3.51 bu corn, $0.28/lb N as anhydrous ammonia, $8.00/ac for anhydrous application, $0.35/lb for UAN applied with herbicide or as a sidedress, and $3/ac for sidedress UAN application. (Updated marginal net return using $5.20/bu corn, $0.75/lb N as anhydrous, $8/ac for anhydrous application, $1/lb for UAN applied with herbicide or as sidedress, and $3/ac for sidedress UAN application.)


2021 Hamilton County Spring Anhydrous N Rate Study

20% wind damage from July 9, 2021 storm. Updated marginal net return using $5.20/bu corn, $0.75/lb N as anhydrous shows essentially no difference in profit for any yield differences observed:

100 lb-N/ac: $1053.40
150 lb-N/ac: $1052.30
200 lb-N/ac: $1051.20


2021 York County Spring Anhydrous N Rate Study

20% wind damage from July 9, 2021 storm. Updated marginal net return using $5.20/bu corn, $0.75/lb N as anhydrous:

130 lb-N/ac: $900.90
180 lb-N/ac: $969.10
230 lb-N/ac: $924.70



2021 York County Timing by N Rate Study

Spring 140 lb/ac: 110 lb/ac N as anhydrous and 30 lb/ac N with herbicide

Spring 190 lb/ac: 160 lb/ac N as anhydrous and 30 lb/ac N with herbicide

Split 140 lb/ac: 50 lb/ac N as anhydrous, 30 lb/ac N with herbicide, and 60 lb/ac N sidedressed at V8

Split 190 lb/ac: 100 lb/ac N as anhydrous, 30 lb/ac N with herbicide, and 60 lb/ac N sidedressed at V8

This study is sponsored in part by the UBBNRD. Updated marginal net return using $5.20/bu corn, $0.75/lb N as anhydrous, $1/lb N as UAN and $8/ac for the sidedress UAN application:
140 lb/ac spring: $1109.50
190 lb/ac spring: $1077.20
140 lb/ac split: $1096.90
190 lb/ac split: $1054.20

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