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JenREES 9-1-19

*I’m grateful to Dr. Richard Ferguson, former Extension Soil Fertility Specialist, for reviewing this article; Dr. Charlie Wortmann, Extension Soil Fertility Specialist, for sharing research-based studies with me; and Glen Slater, SCAL Research Technician, for sharing details of the SCAL study mentioned below.

Nitrification Inhibitors: Two weeks ago, my column included a general overview regarding nitrogen losses in addition to general summary statements based on research. Nitrification inhibitors are best thought of as an insurance policy against loss of applied ammonium-based fertilizer due to excess rain in the first month or so after fertilization. Dr. Richard Ferguson, former Extension Soil Fertility Specialist, and his team have conducted much research regarding the use of nitrification inhibitors over time. Much effort has occurred in sandier soils within the Central Platte NRD. However, an ongoing study at UNL’s South Central Ag Lab (SCAL) near Clay Center is conducted on silt loam soils which are more common in the UBBNRD. Twenty-eight years of this study are summarized here. The majority of the study at SCAL compared Spring pre-plant anhydrous vs. side-dress application with and without the use of nitrification inhibitor N-Serve (nitrapyrin). This product was the product available back in the 90’s. The study actually began by comparing 2 different in-season side-dress applications before switching to pre-plant vs. side-dress in the early 2000’s. Soil samples for nitrate and ammonium content were taken when funding was available. In talking with Dr. Charlie Wortmann, UNL Extension Soil Fertility Specialist, he mentioned that they found yield to be correlated to amount of nitrogen in the soil. A yield increase due to nitrapyrin applied pre-plant was observed in 6 of 28 years with a mean yield change of 2 bu/ac/year. Only 1 of 28 years was a yield increase observed when nitrapyrin was applied in season during side-dress application with a mean yield change of 0 bu/ac/year. In this study, they found that delayed side-dress N with nitrapyrin could reduce plant N uptake. A detailed analysis of nitrapyrin effects on N uptake and soil accumulation from early years of this study can be found in Ferguson et. al (1991). The duration of inhibitor efficacy was measured in other studies where it was found a nitrification inhibitor such as nitrapyrin to last around two weeks with Spring applications. They’ve seen it last as little as 1 week to as long as 6 weeks depending on soil temperatures and moisture. The use of inhibitors is not advised in season as research showed they can release N too slowly for the crop demand resulting in yield loss and/or resulting in increased leaching of nitrogen when it was released too late in the growing season for crop uptake. In general, the research is more supportive for nitrification inhibitor use in sandy soils vs. heavier textured soils; yield benefit to a nitrification inhibitor may be none to a few bushels/acre for silt loam or silty clay loam soils.

In-Season Applications of Nitrogen: In-season application means the nitrogen is applied when the crop is actively growing and utilizing it, greatly reducing potential for loss. Recent on-farm research studies compared side-dress applications using either the UNL equation/Maize N model or industry models such as Climate Field View. In all these studies, the recommended rate was compared to rates that were at least 30 pounds over and under the recommended rate. Some of the studies went as high as +/- 50 lbs/acre compared to recommended rate. I’ve compiled these results in a table at https://jenreesources.com/2019/04/14/jenrees-4-14-19/. Take homes: In none of the studies did the addition of 30-50 lbs N/ac above the recommended rate increase the yield statistically. A few of these studies also compared side-dress applications vs. pre-plant alone. One situation resulted in a statistically lower yield with pre-plant alone while the other two resulted in no yield differences. Many of you have most likely heard of Project Sense in which a grower’s nitrogen application was compared to 75 lbs pre-plant + variable rate in-season application using sensing technology. This project was an on-farm research partnership with Nebraska Extension, Nebraska Corn Board and Corn Growers, and numerous NRDs including UBBNRD. From 2015-2017, 48 site-comparisons were conducted.  The results showed 28.7 lbs less nitrogen was applied using the Project Sense method with a loss of 1.4 bu/ac in yield, and greater profitability of $7.24/ac. All of these results were statistically significant at the 95% level.

To reduce the risk of leaching or denitrification, consider applying the majority of nitrogen close to when crop demand is high with more nitrogen applied during the growing season vs. pre-plant. Also for consideration is the fact that farm operations differ in equipment and labor and growing seasons like 2019 present additional challenges, including for nutrient management.

JenREES 4-14-19

*Note: you may have to turn your cell phone horizontal to more easily read this post.*

Some commented we’ve felt all four seasons last week! This additional weather event didn’t help with stress levels. Disaster stress stages can include heroic, honeymoon, disillusionment, and reconstruction. Heroic was at the beginning of the blizzard/flood disaster. This quickly progressed into the honeymoon phase where we’ve seen an outpouring of support to help with donations, clean-up, etc. It’s very heart-warming and provides some hope in the midst of disaster. While there’s overlap of phases, we’re seeing more of the next stage called ‘disillusionment’ now. This phase can last a year with events like this past week’s weather triggering new anger, grief, loss. It’s during this phase that people more affected by disaster can feel forgotten as others not affected move on with life. And, those not as affected as neighbors/others may experience guilt. For any type of stress, it’s important to talk to a trusted friend, family member, counselor, pastor and not isolate. Unhealthy coping can include turning to substance abuse or other unhealthy options. I’ve been asked what can be done to help. Perhaps the biggest help is to keep praying. Also, keep checking on and reaching out to friends, family, neighbors. These things are more helpful than I can express here! Reminder: the Wellness for Farm and Ranch Families webinar will be held on April 23rd from Noon-1 p.m. at: http://go.unl.edu/farmstresswebinar.

In-Season Nitrogen: I know several were glad to get some nitrogen on last week! For those in NRDs which require nitrogen rates based on UNL recs, it’s important to note that the UNL nitrogen equation uses a weighted average soil nitrate test for the ppm Nitrate. A minimum of 2’ is required. Thus, if you only have a 0-8” soil sample, you have to account for a weighted average or the equation will overestimate the amount of soil nitrate and result in a lower requirement than what may be needed. The Extension circular “Fertilizer Recommendations for Corn” (http://extensionpublications.unl.edu/assets/pdf/ec117.pdf) explains this in detail with an example. There is also an excel spreadsheet that does this for you when you input the depth of soil samples taken. If you’d prefer to use the excel spreadsheet, you can find it at the following website by scrolling to “Corn Nitrogen Recommendations Calculator” https://cropwatch.unl.edu/soils.

With a full soil moisture profile, some have wondered at the impact of using a nitrification inhibitor with their anhydrous this spring. We have a couple farmers testing this and if you’re interested, here’s an on-farm research protocol: https://go.unl.edu/j9dg.

We’ve had some on-farm research studies recently look at sidedress applications using either the UNL equation/Maize N model or industry models such as Climate Field View. In all these studies, the recommended rate was compared to rates that were at least 30 pounds over and under the recommended rate. Some of the studies went as high as +/- 50 lbs/acre compared to recommended rate. I’ve compiled these results in a table at http://jenreesources.com. Take homes: In none of the studies did the addition of 30-50 lbs N/ac above the recommended rate increase the yield statistically. A few of these studies also compared side-dress applications vs. pre-plant alone. One situation resulted in a statistically lower yield with pre-plant alone while the other two resulted in no yield differences. In-season nitrogen studies is our featured on-farm research study this year. You can find protocols at: https://cropwatch.unl.edu/farmresearch/extensionprotocols.

For chemigating fertilizer, often we tend to apply 30 pounds of nitrogen with each quarter inch of water. However, Randy Pryor shared: “did you know that a high capacity injector pump on a pivot can supply 50-60 pounds of nitrogen with a quarter inch of water safely on corn with one application? A soil at field capacity will still intake a quarter inch of irrigation water. Split applications of nitrogen reduces risks with corn injury when the time window is shortened between pre-plant anhydrous applications and corn planting.”

Soil Temperatures: Soil temperatures are available at https://cropwatch.unl.edu/cropwatchsoiltemperature. Your local field and lawn conditions may vary, so you can check with a meat thermometer at 4″ depth. It’s too early for crabgrass preventer. More on that and planting considerations next week.

#NebraskaStrong also means being strong enough to ask for help. Nebraska Family Helpline: 888-866-8660. Nebraska Farm Hotline: 800-464-0258.

*Note: End of column for newspapers.*


 

Nebraska On-Farm Research Corn Yield Results (2015-2018) where Growers Tested a Base Pre-Plant + Varying In-Season Nitrogen Rates

Year County / Irrigation Pre-Plant In-Season Rate/

Yield

In-Season Rate/

Yield

In-Season Rate/

Yield

In-Season Rate/

Yield

Other
2015 Dodge

 

(Maize N Model)

12 lbs N/ac MAP (fall)

80 lbs N/ac 32% UAN at planting

70 lbs N/ac

222 bu/ac

100 lbs N/ac

220 bu/ac

2015 Dodge

 

(Maize N Model)

12 lbs N/ac MAP (fall)

80 lbs N/ac 32% UAN at planting

70 lbs N/ac

221 bu/ac

100 lbs N/ac

221 bu/ac

2016 Dodge

Rainfed

(Climate Field View Model)

78 lbs N as 32% UAN in April 30 lbs N/ac as 32% + 10% ATS (SD)

224 bu/ac

60 lbs N/ac as 32% + 10% ATS (SD)

226 bu/ac

90 lbs N/ac as 32% + 10% ATS (SD)

239 bu/ac

2016 Dodge

Non-Irrigated

(Climate Field View)

78 lbs N as 32% UAN in April 35 lbs N/ac  as 32% +10% ATS (SD)
196 bu/ac
65 lbs N/ac as 32% + 10% ATS (SD)

201 bu/ac

95 lbs N/ac as 32% + 10% ATS (SD)

201 bu/ac

2016 Dodge

Pivot Irrigated

 

70 lbs N/ac as NH3 110 lbs N/ac

247 bu/ac

140 lbs N/ac

250 bu/ac

170 lbs N/ac

249 bu/ac

2017 Dodge/

Pivot Irrigated 4”

70 lbs N/ac as 32% UAN Spring

 

110 lbs N/ac 32% (SD)

 

239 bu/ac

140 lbs N/ac 32% (SD)

 

243 bu/ac

170 lbs N/ac 32% (SD)

 

251 bu/ac

210 lbs N/ac 32% Spring Pre-Plant

216 bu/ac*

2017 Saunders

Non-Irrigated

100 lbs N/ac as 32% UAN Spring 40 lbs N/ac 32% (SD)

195 bu/ac

40 lbs N/ac 32% + Humic Acid (SD)

199 bu/ac

75 lbs N/ac 32% (SD)


200 bu/ac

140 lbs N/ac 32% Spring Pre-Plant

193 bu/ac

2017 Saunders

Non-Irrigated

100 lbs N as 32% UAN Spring

 

40 lbs N/ac 32% (SD)

183 bu/ac

40 lbs N/ac 32% + Humic Acid (SD)

183 bu/ac

75 lbs N/ac 32% (SD)

185 bu/ac

140 lbs N/ac 32% Spring Pre-Plant/

185 bu/ac

2018 Gage

Non-Irrigated

150 lbs N as 32% UAN in April. Rye cover crop. 0 lbs N/ac as AMS  (SD)

137 bu/ac*

50 lbs N/ac as AMS (SD)

161 bu/ac

100 lbs N/ac as AMS (SD)
151 bu/ac
2018 Franklin

Pivot Irrigated 4”

 

None. Cover crop mix. 0 lbs N/ac as Urea broadcast

210 bu/ac *

100 lbs N/ac  as Urea broadcast

254 bu/ac

175 lbs N/ac as Urea broadcast

272 bu/ac

250 lbs N/ac as Urea broadcast

275 bu/ac

*Denotes that treatment was statistically different from others for a given year and location at the 90% confidence level. All other treatments without this denotation are not statistically different although they may be numerically different due to variability.

(SD) = Sidedress application

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