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ABOUT ME

osunpk

osunpk

Since 2008 I have served as the Precision Nutrient Management Extension Specialist for Oklahoma State University. I work in Wheat, Corn, Sorghum, Cotton, Soybean, Canola, Sweet Sorghum, Sesame, Pasture/Hay. My work focuses on providing information and tools to producers that will lead to improved nutrient management practices and increased profitability of Oklahoma production agriculture

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Nitrogen Management Report Card

During January and February I spent a lot of time on the road giving precision ag and wheat yield / protein talks. One thing about giving the same talk multiple times and spending countless hours on the road, about 70, is the time you have to think about the little things in your talk. This time around it was the slide below. The graph is from the 502 Long Term Fertility study located in Lahoma OK. When I first put the slide together in 2016 the purpose was to show how the yield and optimum fertilizer rate is extremely varied. I went in to the 55 plus years of yield data and pulled out the past ten years and identified the nitrogen treatment, only those with full P and K fertility, that economically maximized yield each year. With the graph I was able to show how the nitrogen rate required to maximize yield changes dramatically each year and where the amount of N was not directly correlated with yield. But after showing this graph a few times I thought that added lbs of N per bushel would help me highlight the point about changing N demand. That’s the blue numbers below each year. And of course out of curiosity I averaged the numbers. The ten year average was 1.5 lbs of N, which would suggest over a ten year period you would need to apply 120% of the N removed to optimize profit.

Yield and Nitrogen Rate

Selected data from the long term winter wheat study locate in Lahoma, Oklahoma. Study consist of a range of nitrogen, phosphorus, and potassium rates and combinations. The orange bar the grain yield of the plot with the economic optimum yield and the black bar is the N rate associated with the yield. The blue values on the bottom is the lbs of N required per bushel.

 

The 1.5 lbs per bushel over time was an important number. Not long before I had reached out to half of dozen producers that I have spent at least 5 years with working on their N management. My question to them, what was your average yield and average N rate over all your fields and years. Turns out that most of these producers who were using N-Rich strips and making 2 or 3 trips over the field were averaging 1.5-1.6 lbs N per bushel of wheat produced across a farm. Of course when they told me this I was excited, that’s such an improvement over 2.0 lbs of N per bushel.

The real thought came with me combining these two independent tid bits. Can we provide a Nitrogen Management Report Card  if we look at several years of yield history? Let me preface what is presented below is not a scientifically tested or proved concept, yet. The more I think about it the more I am beginning to think that YES we can do a beneficial postmortem analysis. This is not a 1 year analysis, in fact based on the long term data I have been looking at there needs to be 5 years of data per field evaluated.  I also strongly contend that this is a by field process. This will provide the opportunity to look at management over a broad spectrum of soil types and weather.

The calculation for lbs of N per bushel is not tough. In a continuous grain only winter wheat system you would add up the amount of nitrogen applied per acre over the period you are evaluating. Sum up the annual average grain yield and multiple that value by 1.3.  Divide the total N applied by the total N removed per acre.  This will be a decimal value, to compare with the tables below multiple by 100 to get a percent.  Based on the long-term trials there needs to be at minimum five years of data.  But the more the better.

Pounds of nitrogen removed per one unit of yield harvested. These values are generalized averages and can change based on environment, management, and cultivar.

 

I would like to reiterate the grades provided below were not developed from any given data set. The report comments are of my own opinion. I do hope in the near future to utilize the Oklahoma State University long-term fertility studies to refine these tables.

Wheat only 2

The Nitrogen Management Report Card for a continuous winter wheat grain only system. The first column is lbs of N per bushel, the second column is the percent of nitrogen applied per pound removed. The last column is the report on your nitrogen management strategy.

For a field with a crop rotation the way to calculate is the same you will just need to go into each harvest and multiple yield by the N in the crop, then sum up those values.

Crop Rotation, no-legume 2

The Nitrogen Management Report Card for a Crop Rotation that does not include a legume. The first column is the percent of nitrogen applied per pound removed. The last column is the report on your nitrogen management strategy.

For a field with a crop rotation with legume (or cover crop), I have adjusted the grade scale with the assumption less total N will be needed due to the addition of N fixed by the legumes.

Rotation with Legume 2

The Nitrogen Management Report Card for a Crop Rotation including a Legume.  Legume nitrogen removal is not accounted for however grades are changed assuming some level of nitrogen fixation. The first column is the percent of nitrogen applied per pound removed. The last column is the report on your nitrogen management strategy.

Hopefully with concept will give you a different way to evaluate your N management strategies.  This will not and cannot tell you what you need to apply next year. I mean just look at the data from Lahoma, from 2011 to 2015 optimum N rate ranged from 0 to 100 lbs N pre acre and N per bushel grown ranged from 0 to 2.2. Also as you look at the charts, understand that if you follow the old rule of thumbs 2.0 lbs N per bushel winter wheat and 1.2 lbs N per bushel for corn and sorghum, you are likely in the RED. These values are not that wrong for yield goal, 100% preplant application nitrogen management strategy. It is just with today technology, equipment, and agronomic practices we can do a lot better.

My final recommendations/comments would be:

1) If you are in the greens and yellows you are overall doing well. However there is always room for improvement. Are you currently accounting for the temporal variability in N demand, how about the spatial variability?

2) If you are in the orange and reds on the low side, are you there because you are underestimating yield or you are applying less because of grain prices?
There is likely money to be made by increasing yields with a little more nitrogen in these fields.

3) If you are in the orange and reds on the high side, are you there because you are consistently overestimating yield? Perhaps your yield estimation is not off but your lbs of N per bushel value is too high? Are you applying all of your N pre-plant. This practice is the most inefficient way, in terms of N use efficiency, to fertilize.

Questions or comments?

Please feel free to reach out to me via email or phone.
b.arnall@okstate.edu 405-744-1722

Re-Post: Sensing the N-Rich Strip and Using the SBNRC

This the recent rains across the dry wheat belt the N-Rich Strips are going to start showing up. Because I am re-posting ans older blog that walks users through the sensing process and inputting data in to SBNRC. But since post we have also release a iOS version of the Online Calculator. iOS N-Rate Calc

Original Post:
With the significant swing in temperature over the last few weeks many are chomping at the bit to get outside.  The wheat is starting to respond to the good weather and N-Rich Strips are showing up around the state.  Over the past week I have had several calls concerning the impact of the cold weather on the N-Rich Strips.  Many of the fields either are still small due to limited days of warm weather and growth or may have a good deal of damage to the foliage.  If the field of concern has only a little or no damage and the strip is visible, the time to go is NOW, but if you cannot see the strip and your field has tissue damage or is small, similar to the first two images, then you will need to wait a week or two for sensor based recommendations.  Another situation fits with the third image, the field has freeze damage but the N-Rich Strip is also visible.   In this case the predicted yield level would be reduced do to the dead tissue making the N rate recommendation a little off.  I still however recommend using the sensor and online SBNRC (http://www.soiltesting.okstate.edu/SBNRC/SBNRC.php) to make or base top-dress N rate.  Even if the recommendation is a little off it will still be much more accurate than just guessing. However you must look at the SBNRC and ensure that it makes agronomic sense, if it does not consult your county educator or myself.   This is discussed in more detail in my earlier blog about freeze damage.  Keep in mind no matter what, if you can see the N-Rich Strip, everything outside of the strip is suffering from nitrogen deficiency.  Decisions and fertilizer applications need to be made soon, to maximize yield.

Winter Wheat and Nitrogen Rich Strips.

Winter Wheat and Nitrogen Rich Strips.

Regardless of whether or not the strip is visible you should be planning to sense with the GreenSeeker Handheld very soon. Remember the sensor has the ability to detect differences before your eyes can.   To sense the N-Rich Strip and Farmer Practice the user should carry the sensor approximately 30 to 40 inches above the crop canopy while holding the sensor level over the crop.  While you are walking the two area the trigger should be held the entire time.  I recommend walking at minimum 100 paces for each.    The average NDVI value seen on the screen will only stay on the screen for a few seconds.  Therefore it is critical you have a method of recording the number for later use. The sensor has limited memory so it will time out is the trigger is held for an extended period of time.  If you wish to collect more NDVI readings just do it in multiple trigger pulls recording each.  Once you have the average NDVI for the N-Rich Strip and Farmer Practice you can go to the SBNRC site mentioned above to retrieve the N rate recommendation.   Once in the calculator, for those in Oklahoma, choose the “within Oklahoma” option in the bottom left hand corner of the screen.  This will allow the calculator to access the Oklahoma Mesonet to determine growing degree days.  After the location is picked from the options you will need to enter Planting Date and Date Prior to Sensing.  Additional information requested is the expected grain and fertilizer prices.  While these inputs will provide some economic evaluations they will not impact recommended N rate.

GreenSeeker HandHeld NDVI Sensor

GreenSeeker HandHeld NDVI Sensor

Below is a YouTube video in which I describe how to use the GreenSeeker to collect NDVI readings, describe the data needed to complete the online calculator, and how to interrupt the calculators output.

Poly versus Ortho another year of data from Iowa

Guest Author, Dr. Jake Vossenkemper; OkState Grad and Agronomy Lead, Liquid Grow Fertilizer

Updated Research Comparing Ortho/Poly-Phosphate Ratios for In-Furrow Seed Safe Starter Fertilizers. Last years post Link

Article Summary

  • Ortho-phosphates are 100% plant available, but a high percentage of poly-phosphates in starter fertilizers convert to ortho-phosphate within just two days of application.
  • This quick conversion from poly- to ortho-phosphate suggests expensive “high” ortho starter fertilizers are not likely to result in increased corn yields compared to seed-safe fluid starters containing a higher percentage of poly-phosphate.
  • On-farm field studies conducted near Traer, IA in the 2016 and 2017 growing season found no statistical difference (Pr > 0.05) in corn yield between conventional and high ortho-phosphate starters in either year.
  • High ortho starters cost more per acer than 50/50 ortho:poly starters, but do not increase corn grain yields.

Polyphosphates Rapidly Convert to Plant available Orthophosphates

Given polyphosphates are not immediately plant available and orthophosphates are immediately plant available, this gives the promoters of “high” orthophosphate starters ample opportunity to muddy the waters. Nevertheless, the facts are, polyphosphates are rather rapidly hydrolyzed (converted to) into orthophosphates once applied to soils, and this hydrolysis process generally takes just 48 hours or so to complete.

In September of 2015, we posted a blog discussing some of the more technical reasons why the ratio of ortho to polyphosphates in starter fertilizers should have no impact on corn yields. For those that are interested in the more technical details, we encourage you to follow this link to the September 2015 blog post.

While we was relatively certain that the ratio of ortho to polyphosphates in liquid starters should have no effect on corn yields, we decided to “test” this idea with on-farm field trials located near Traer, IA in the 2016 and 2017 growing seasons.

How the Field Trial Was Conducted

In these field trials, we used two starters applied in-furrow at 6 gal/ac. Each starter had an NPK nutrient analysis of 6-24-6. The only difference between these two starters was the ratio of ortho to polyphosphates. One of these starters contained 80% orthophosphate and the other contained just 50% orthophosphate. With the remainder of the phosphorus source in each of these two starters being polyphosphate. Each plot was planted with a 24-row planter (Picture 1) and was nearly 2400 ft long. In both the 2016 and 2017 growing seasons the experimental design used was a randomized complete block with 4 or 5 replications.

Field Trial Results

Averaged over the side-by-side replications there was less than 1 bu/ac difference in corn grain yield between the high ortho and low ortho polyphosphate starters in both the 2016 and 2017 growing seasons. In addition to finding no differences in grain yield between these two starters, the high ortho starters generally cost about $1 more per/gal (so the $6/ac difference in price at a 6 gal/ac rate) than the low ortho starters. So the more expensive high ortho starter clearly did not “pay” its way in our multi-year field trials.

More Trials Planned for 2018

While our findings agree with other research-comparing ortho and polyphosphate starter fertilizers (Frazen and Gerwing. 1997), we want to be absolutely certain that our fertilizer offerings are the most economically viable products on the market. Therefore, we have decided to run this same field trial at one location in northern, IL in 2018, and at one location in central, IA in 2018. Stay tuned for those research results next fall.

References
Franzen D. and J. Gerwing. 2007. Effectiveness of using low rates of plant nutrients. North Central regional research publication No. 341. http://www.extension.umn.edu/agriculture/nutrient-management/fertilizer-management/docs/Feb-97-1.pdf (accessed 8 of Sept 2015).

A big Thank You to Dr. Vossenkemper for sharing this article with us.
The original article and his contact can be found at Link

Its Dry and its Time to Top-dress.

Normally the alarm for beginning wheat topdressing gets sounded right away in early January. However, it might be understatement to say this year has been dry so far – “drier than a popcorn fart” may be a better description. At the time of writing this blog, a significant portion of the Oklahoma wheat belt has now gone 90+ days with less than 0.25” of rain. The great folks at Mesonet reminded us on January 18 that the long term forecast is not providing us much hope either.

Mesonet Dry Twitter

The Oklahoma Mesonet tweet from Jan 18th the current lack of rain status and the impending lack of more rain. 1.18.2018

Because it has been dry and no significant rain is in the current forecast, the question is what do we do now about topdressing? This is a tough question to answer as there is not a really “good” option at the moment to be honest. Here are some thoughts to consider:

 

  • In the parts of the state where it is dry and dry deeper than the majority of the rooting zone (> 6”), we should not worry about filling up the nitrogen tank as long as the water tank is empty. As it stands currently, the best option is to hold off for now and wait to apply topdress N right in front of a real chance of rain. The good news is we still have some time yet to get N applied and not limit yield potential if we do get that rain. Ideally, we need the N down in the rooting zone just prior to jointing. Several things, including the number of potential grain sites, are determined just prior to jointing, and it is imperative that the plant has the fuel it needs to complete these tasks. Jointing occurs around the end of February in southern OK and around the second week of March in northern OK. Jointing also marks the beginning of rapid nitrogen uptake by the plant which is used to build new leaves, stem, and the developing grain head. The nitrogen stored in these plant parts will be used to fill the grain later in the season, and the plant is dependent on this stored nitrogen to complete grain fill. And while it does seem like it right now, we still have the potential to make a decent crop if we can get rain before we break winter dormancy. If we do not get the rain though soon as it is appearing, we will not have spent as much money on this crop by holding off on topdress N, and the likelihood of getting the return on our N investment goes down as our yield potential goes down.
  • What we can and should do right now is apply N-rich strips. An N-rich strip can help put your mind more at ease by taking the guesswork out of knowing if nitrogen needs to be applied and how much should be applied. The N-rich strip can be as simple as using a small lawn fertilizer spreader with a bag of urea. You local county extension educator can also provide more information on N-rich strips and even has access to lending small fertilizer spreaders!

 

For those producers who have too much ground and cannot cover all of it just prior to a rain or for those who want to apply now as they are worried about nitrogen being limited after it does start raining, here are few more considerations:

  • For conventional-tilled fields that have limited to no residue, applying UAN through streamer nozzles is an okay option. Why? With UAN, there is a very high percentage of soil-fertilizer contact. This immediately improves the efficiency compared to urea. In fields with crop residue, flat fan nozzles are not recommended right now as the likelihood up of N tie-up is too high.
  • For no-till fields, the two big concerns are ammonia (NH3) volatilization with dry urea and tie-up on the residue with liquid UAN. Picking the best option in this scenario is a much tougher decision with not a real good conclusion. So, here it goes. If there is tall standing stubble with dry soil below, the dry urea gets the edge. Why? If the stubble is not in a mat, the urea prill can work its way down towards the soil surface. If it can get there, it is out of the high winds, and it will remain there until we get a rain, heavy dew, or increase in humidity. Is there still a chance for loss due to volatilization? Absolutely. Again, it goes back to whether there is any chance that you can wait to apply?
  • There have been some questions about using urease inhibitors with broadcasting urea. That is a good question, but it is hard to make an argument for their use until we get a good chance of rain in the 10-day forecast. Typically, these products do not have the life span to hold off urease (i.e., the enzyme that breaks urea into NH3) for more than 10-12 days.

The latter points also apply to those who use the local co-op or ag retailer for application.  Some of these groups require 30 days or more to cover all of the acres they service.

Since it is dry and we still have some time yet to apply N, this may turn out to be the perfect year to topdress urea with a grain drill. For those interested in this method, you can find research results from last year on this topic, as well as a calibration guide, by clicking here . More information about nitrogen applications that are “thinking outside the box” can be found by clicking here.

 

Tye Urea

Using a 3pt Conventional double disk tye drill to apply urea in-season

For more information contact Brian Arnall or David Marburger.

 

 

 

Managing Protein in Hard Red Winter Wheat.

A result of the 2016-17 winter wheat crop was a significant amount of discussion focused on protein levels. For two years running now, the protein levels have been low across the board.  Low protein brings in a challenge to sell, could impact local basis, and even more concerning is that low protein is an indicator that nitrogen was limiting during grain fill. Therefore, the field maximum yield potential was not achieved. In this blog, we talk about what protein is, what can be done to maintain a good protein level, and what can be done to increase protein if desired.

First, the definition of protein is any of a class of nitrogenous organic compounds that consist of large molecules composed of one or more long chains of amino acids and are an essential part of all living organisms, especially as structural components of body tissues such as muscle, hair, collagen, etc., and as enzymes and antibodies. Protein is also one of the many attributes that determines end-use quality and marketability of winter wheat. Sunup TV met with Dr. Carver in the baking and milling lab to create a great video discussing wheat quality impact on baking and milling.

 

We determine protein by measuring the percent of nitrogen in the grain and multiplying by a factor of 5.7. So if the grain has N % of 2.5, the protein content is 14.25.  The amount of N in the grain is affected by many variables such as weather during grain fill, yield level, and N availability during grain fill.  If weather is conducive to good grain fill and test weight is high, we will often see protein values dip. On the other hand when grain fill conditions are hot and dry and we have light test weight, wheat protein will be higher. Research has shown (Figures 1 and 2) that generally as yields increase protein levels decrease. Of course if N is limited during grain fill, the N available for the grain is reduced, and the plant is forced to get all grain N from re-immobilizing N in the leaf tissue.

Fig 1, Yield and protein averages from all of the OkState Long Term fertility trials. Data courtesy Dr. Bill Raun.

Fig 2, Grain protein and yield of from intensively managed wheat. Data Courtesy Dr. Romulo Lollato KSU.

 

Maintaining Protein, and yield.

Managing nitrogen to maintaining protein and maximizing yield comes down to making sure that N is available at critical growth periods. With wheat, the critical uptake stage is typically the time frame between hollow stem and soft dough.  The two graphs below show nitrogen uptake in wheat and barley.  If the same graph was made for dual purpose wheat, the upward swing would start sooner but would follow the same general trend.

Fig 3, Nutrient Uptake of Wheat found in “Agricultural and Biological Sciences » “Crop Production”, ISBN 978-953-51-1174-0, Chapter 5 By Juan Hirzel and Pablo Undurraga DOI: 10.5772/56095″

Fig 4, Nitrogen uptake in Barley at two nitrogen rates. http://apps.cdfa.ca.gov/frep/docs/N_Barley.html

When it comes to making sure N is available during this time of peak need, the only way we can do that is apply just before it is needed.  This means split application.  While putting all the nitrogen out pre-plant as anhydrous ammonia is the cheapest method, it is also the method that provides the lowest nitrogen use efficiency and is most likely to show deficiencies late in the season. One of the challenges with 100% preplant N application is that years with good yield potential coincide with years with good/high high rainfall, which means more nitrogen loss.  Some interesting results from studies implemented in the 2016-17 cropping season showed the importance of nitrogen application timing. The study is determining how long nitrogen application can be delayed after the N-Rich strip becomes visible (https://osunpk.com/2013/09/19/nitrogen-rich-strips/). For the study, 90 lbs of N was applied on one of the treatments at planting When that plot became visibly greener or bigger than the rest, N application was triggered. After the 0 DAVD (Days after visual difference where the day had growing degree days >0), another treatment was applied every 7 growing days for 63 growing days.  Each plot, excluding the zero N check, received 90 lbs as NH4NO3 (we use this to take the variable of volatilization out of the data). In all cases, 90 lbs applied in late January to early February was better than 90 lbs pre-plant. Keep in mind there was 0 N applied at planting for each DAVD application timing; yet, we still hit 50-80 bushel wheat with nothing but in-season N. This is the result of supplying the N when the plant needs it. I should add this is just one year of data, and every year is different. The study is being replicated again this year and will be highlighted at the Lahoma field day.

 

Fig 5, Results from the 2016-2017 delayed nitrogen study led by Mr. Joao Bigato Souza. The trials consisted of a preplant plot, unfertilized check plot, and then a series treatments in which N application was based on days from a visual difference between the pre-plant and check. All fertilized plots received 90 lbs N as NH4NO3. DAVD is days after visual difference. (Error in bottom left graph, the last date should be March 27 not April 4)

For dual-purpose wheat, the total amount of N expected for the forage production needs to be applied pre-plant. Oklahoma State recommends 30 lbs N for every 1,000 lbs of forage expected For grain-only wheat, there needs to be only 20 to 40 lbs of N available to the crop when planted (this includes residual N). The remaining N should be applied at green up or early spring.  The only way to ensure that N is applied when the crop needs it is to utilize the N-Rich Strip method. Having a N-Rich strip in your field lets you know when the wheat needs more nitrogen and when it does not.

Fig 6. Nitrogen Rich Strip (N-Rich) showing up in a No-till wheat field.

Two years testing the N-Rich Strip and Sensor based nitrogen rate calculator (SBNRC) from the Texas boarder to the Kansas boarder showed that the SBNRC on average reduced N but maintained yield and protein when compared to standard farmer practice (Table 1).

Table 1. Results from testing the Nitrogen Rick Strip and Sensor Based Calculator Method across Oklahoma wheat fields.

Increasing Protein

Some producers may plan to market high protein for a premium if available.  Fortunately, there are opportunities to increase protein via management. While most of the strategies for increasing protein happen later in the growing season, some of the early decisions can be a significant contributing factor. Variety selection and keeping the plant healthy and free of competition (i.e., pest management) throughout the growing season are going to increase the opportunity to produce high protein wheat.  After that, the equation goes back to Figures 3 and 4 and making sure the crop has access to nitrogen during peak periods, including grain fill.  If you will note, the bottom two graphs of Figure 5 both show significant increases in protein on the later applications. For both locations, this was when N (90 lbs N ac-1) was applied after full flag leaf emergence.  There has been a significant amount of work at OSU looking at late application of N stretching back into the 1990s http://nue.okstate.edu/Index_Publications/Foliar_N_Curt.pdf. The focus has been looking at timing, source, and rate. The take home of decades of work can be summarized as such.  Yes, protein can be increased with late season application, but not always. Applying N at or after flowering has a significantly greater probability of increasing protein than a application at flag-leaf. Source of N has had little impact if managed properly (UAN, 28-0-0, has to be watered down so that it does not burn the plant). The rate of N does matter quite a bit. Most of the work suggests that for every pound of N applied, the percent grain protein could increase by .05%. So to increase protein from a 12.5% to 13.5%, it would require approximately 20 lbs of N per acre.  My work has shown the same trend that a 20 lbs application at post-flowering had more consistent increases in protein than lower rates at the same time or similar rates applied at flag leaf.

This wheat season we are looking to improve our knowledge of management on protein content through multiple studies by continuing the evaluation of varieties and management practices.

If you have any questions for comments please feel free to contact me.
Brian A.
B.arnall@okstate.edu

2017-18 Wheat, Nitrogen Outlook

Its that time of year and I wanted to share my thoughts on nitrogen (N) management in the up and coming winter wheat crop. This season is already shaping up to present certain challenges and opportunities. This blog will highlight many of the topics that were brought up in a recent Sunup TV shoot, video below.

This summer the price of Anhydrous Ammonia (NH3) dropped and producers made a run on NH3 for graze out and dual purpose ground. Currently the price of N is still lower than it has been than it has been in a while and producers are are taking advantage.  All things are lining up for this fall to be a good forage year, nitrogen prices are low and we are going into September with a decent soil moisture profile across the wheat belt.  If producers can get into the field in a timely manner and we keep getting timely rains it will make a great forage crop.  But here is my cautionary statement, if this is a good forage year we are shaping up to be short on N by spring. First the market place over the past two years has overall reduced the amount of inputs into the wheat crops and I would say across the  board a lot of the wheat ground is starting out this season with very little residual N.  Secondly and more importantly everything which makes for a good forage year makes for a good N loss year, for Oklahoma good rain usually makes good forage. While NH3 does immediately convert to the non mobile ammonium (NH4) form, when soils are warm and moist it does not take long to convert to the mobile and leachable nitrate (NO3) of N. In a recent study looking at N applied at planting in corn, the majority of the NH4 had converted to NO3 by V4, which is usually four to five weeks after planting. Which means NH3 applied in August is likely completely converted to NO3 by September and susceptible to leaching (Since starting this blog in August we have seen a dry down, note the soil moisture on 9.7.17, and abundance of army worms).  As the story line has been the low protein wheat of the 2016 and 2017 harvest attention needs to be paid to the crop going into spring.

The 1-day Average 16-inch Plant Available Water map from http://www.mesonet.org. Accessed 8.28.17

The 1-day Average 16-inch Plant Available Water map from http://www.mesonet.org. Accessed 9.07.17

At Minimum MASS BALANCE the system for dual purpose. 
The most simplistic approach to nitrogen management this year is the evaluate what has been made for beef gain and what will be needed for wheat grain yield come the spring. The general rule of thumb is that is takes 1000 lbs of forage to produce 100 lbs of beef gain and depending on the N concentration 1000 lbs of wheat forage will have about 20 lbs N tied up in it. As I talk about on a regular basis, nitrogen use efficiency is not 100% so OSUs rec is 30 lbs of N for each 100 lbs of gain/ 60 lbs of N per ton of forage.  On the grain side the standard rule of thumb is 2 lbs of N per bushel. So if the producer applied 100 lbs of NH3 (82 lbs of N) pre-plant and in the spring the average gain is 200 lbs per acre there is only 22 lbs left over for the grain.  At that point if we use the field historic average grain yield, lets assume 30 bushel, there needs to be about 38 lbs of N added.
22 lbs (left from pre) / 2 = 11 bushels. 30 – 11 = 19. 2 lbs N per bushel * 19 bushel = 38 lbs of N.

Grain Only Systems
More and more of the grain only producers I am working with are using a 3 pass fertility approach. The approach works this way, No pre-plant N is applied except for what goes down with the seed.  In all scenarios this is 40-80 lbs of 18-46-0 which delivers 7 to 14 lbs of N above what is already in the soil (residual N). The second pass comes in winter to early spring before green-up where they are typically applying about 60+ lbs of N.  The third pass happens prior to hollow stem.  At this point the producers are taking stock of their crop.  If the stand is good and soil moisture is good the final application tops them off for the rest of the season.  This system is really aided by the application of an N-Rich strip https://osunpk.com/2013/09/19/nitrogen-rich-strips/  . The strip allows the producers to observe the system and know exactly when nitrogen is limited and applications need to be made. Utilizing the Sensor Based Nitrogen Rate Calculator https://osunpk.com/2014/02/24/sensing-the-n-rich-strip-and-using-the-sbnrc/  provides an exact value to the nitrogen needed.
The approach of putting on nitrogen in-season will not only increase the efficiency of the N applied but will help in producing a wheat crop with a good final protein value.

For those wanting to go with the more traditional N application approach of 2 passes I prefer to have no more than 50% of the planned N down at pre-plant. This will allow for a spring green up based upon yield goal.  If using the N-Rich strip in a two pass approach I like to see about 30-40 lbs down at pre-plant and then use the N-Rich Strip and SBNRC to fine tune your top-dress which will take place in the spring. Using this technique the research from OSU shows the we can both maximize yield and nitrogen use efficiency.

For the Full Story watch the Sunup TV YouTube video below.

 

N-Rich Strip Applicator. Push Spreader that can be purchased at any local hardware store.

 

 

 

 

 

 

Using a Grain Drill Grain Box for Fertilizer, Results and a Calibration guide.

For the last few years I have been challenging people to “Think Out Side the Box” when applying fertilizer. One of these application methods is to use a grain drill to put Nitrogen fertilizer into the soil. Just the act of getting N into the soil will immediately decrease the opportunity for losses. While it seems crazy many picked up on the idea of using grain drills for N applicators. The first year of a two-year study looking at documenting the practice is in the books. With data coming in from three locations, utilizing two drill types (double disk conventional and single disk no-till), the results are quite promising.  The biggest take home from year one was a 2 parter: 1) if conditions are conducive to nitrogen loss from urea volatilization, applying urea with a grain drill in the spring improved efficiency. Conversely if loss potential was low, there was no difference. 2) in some soil conditions the double disk drill could not close the furrow and this reduced the positive impact of using the drill.  The two tables below show the impact application and environment on yield.  Each of the treatments had 60 lbs of nitrogen (as Urea) applied per acre. At Chickasha the first application was made while it was fairly dry and then it rained, but the second application was made during a period in which there was no rain but a fairly significant dew each morning. This can be seen as the small effect volatilization played on the yields of the first application timing. At Lahoma, it was the early applications that had a higher risk of loss with no difference seen later.

 

Partial year one results from the topdress N with a grain drill at Chickasha OK. Timing 1 was late January and timing 2 was late February.

 

Partial year one results from the topdress N with a grain drill at Lahoma Ok. Timing 1 was early January and timing 2 was mid February, and timing 3 was early March.

 

With the results from the first year of the top-dressed drilled nitrogen studies in the books, the interest has been increasing. One question keeps popping up: for grain drills without a fertilizer box, what  do we put our grain box on to apply fertilizer.  At one point the number of inquires hit a critical mass and I sent out my crew to find grain drills and create calibration curves for DAP (18-46-0) and Urea (46-0-0).  The crew did just that.

Now please consider what is presented below is a general calibration. Much like the chart on your grain drills, it will hopefully get you close but the best-case scenario is that each drill is calibrate prior to running. As request are made we will try to add more drills to this list.

To create the following charts the guys located several different makes of drills around the OSU experiment stations. They were instructed to choose setting based on the manufacture seed rate charts in the range of 60, 90, 120 etc.  For each setting they caught a couple of row units for both Urea (46-0-0) and DAP (18-46-0). They caught each setting multiple times to get a good average.

If you look at the tables you can see the Landol 5211, Great Plains 1006NT, and International 5100 are fairly similar, with the John Deere 1560 being a little lower and the John Deere 450 significantly lower at the lower rates.  To use the tables below, consider what kind of grain drill you have and choose to follow one of the drills listed or the average of all five. If you use the average value I would expect most to find they applied a bit more than planned.  To make it even simpler, but less accurate, you can use the % wheat value.  To do this for DAP take your target rate and divide by .88, this value is what you want to set your drill to.  For example for a target rate of 100 lbs DAP per acre use the following formula:  100/.88 = 114.  Choose the manufacturer recommended settings 114 lbs wheat seed per acre.   If you are wanting to apply Urea take your target rate of urea and divide by 0.71.

 

DAP 18-46-0

Table showing the manufacturer wheat rate setting and the resulting amount of DAP 18-46-0.

Graph documenting the manufacturer wheat rate setting and the resulting amount of DAP 18-46-0.

UREA 46-0-0

Table documenting the manufacturer wheat rate setting and the resulting amount of Urea 46-0-0.

Graph documenting the manufacturer wheat rate setting and the resulting amount of Urea 46-0-0.

 

Again, I cannot state this enough, this is a general guide, each drill even of the same manufacture and model will likely be different.  The only way to be certain of the rate applied is to calibrate each drill individually.

Questions or comments please email me at b.arnall@okstate.edu or call 405.744.1722