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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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Yellow Wheat the 2020 Edition.

I have been trying to write this blog addressing the yellow wheat for about two weeks now. But with finally finding a dry”ish” day or two and a lot of calls and emails about yellow wheat, I am just now getting to it.
So the short story is there is a lot of wheat out there in the state that is show signs of chlorosis, or yellowing. I wish I could say I have all the answers for you in this article, but I will have to lay heavily upon the agronomist best answer, “Well it Depends.”.

Cow pox showing up in a wheat field in Kay County.

First we will start with the things I know least about and then move on to things that are more in my wheelhouse. In the last two weeks I have been on multiple email strings trying to chase down the cause of chlorosis in fields all over the state.  One of these included Dr. Bob Hunger and the Plant Disease & Insect Diag Lab (PDIDL) and in one field his final thought was “So, my best guess is cold and wet soils along with fungi colonizing the older leaves that are starting to senesce.” At the same time I am finding regular occurrence of Tan Spot and Leaf Rust increase. All these pathogen cause some level of chlorosis and if you do not get down and pull some samples you will never know the cause.

Originally thought to be leaf rust, but corrected by Dr. Hunger who suggested it is early stages of striped rust, found in Stillwater Oklahoma 3.27.2020.

 

A new for me this year is what I am calling the herbicide ding. I was able to get over a lot of my wheat that first week of March with a shot of herbicide, everything was almost to hollowstem. The wheat really got dinged. Very visual yellowing and stunting of the plants. Talking with Dr Manucheri, she had seen the same thing in her plots in Tipton. I have also visited several farmer fields with the same symptoms. Dr. Manucheri shared with me the Finesse label. Directly from the label “Temporary discolorations and/or crop injury may occur if herbicide is applied when the crop is stressed by severe weather conditions (such as heavy rainfall, prolonged cold weather, or wide fluctuations in day/night temps), disease or insect damage, low fertility, applications to course soils, or when applied in combination with surfactant and high rates of liquid fertilizer solutions.” This can be found on page 5, http://www.cdms.net/ldat/ldFSL002.pdf . You can just about mark off every weather and application condition mentions, on the same field.

Image collected 3.25.20. The right side was treated with Powerflex on 3.5.20. The left side was not treated so that sorghum could be planted in April.

Now to the yellow wheat I can comfortably talk about. There is nitrogen deficiencies out there. That should not come as a shock with the amount of rain we have received over the last couple months. I also believe that a fair amount of the wheat crop out there is a bit lacking on roots department.

 

The overarching wet cools soils that we have more than likely have led to reduced root exploration in some areas. And if you combine short roots with a nitrate leaching then the probability of N being out of the reach of the crop is high. Then the question is “Is there still time to do anything?”. The trip I look over the weekend (3/28, 3/29) that encompassed a great deal of the North Central Ok wheat belt showed me that the majority of the wheat had really progressed physiologically in the last two weeks. At this point, a positive return on N investment hinges on the stage the wheat is at.

Our delayed N work over the past several years show that we have maintained the yield on our trials even when fertilizer was delayed into the first week of April. https://osunpk.com/2019/08/14/how-long-can-wheat-wait-for-nitrogen-one-more-year-of-data/

Each graph is from a location where the delayed N study was preformed. The objective of our study was to determine the impact of prolonged nitrogen deficiency on winter wheat grain yield and protein. Eight studies were conducted with 11 N application timings in no-till dryland conditions. A pre-plant treatment of 90 lbs ac-1 of N was broadcast applied as ammonium nitrate (AN). We used AN as our source because we wanted to measure the crops ability to recover and eliminate the impact of source efficiencies. When visual symptom differentiation (VSD) was documented between the pre-plant and the non-fertilized check, i.e the N-Rich Strip showed up, top-dress applications were performed every seven growth days (GDD> 0) (https://www.mesonet.org/index.php) until 63 growth days after VSD at all sites. The only N the treatments received where applied according to treatment structure. No pre-plant N was applied on the trials other than the Pre-plant treatment.

This table shows the application dates of the 10 site years of the delayed nitrogen study. The first column is the location, to the right of the location is two rows the top is grain yield and the bottom is grain protein. Each of the following columns corresponds to an application date. Applications began at each study when the The colors are related to whether that application was statistically (Alpha=0.05) worse than, equal too, or better than applying nitrogen at the first sign of deficiency (0DAVD). For this comparison it is important to know that at no location did preplant have significantly greater yield than 0DAVD.In the majority of those years that first week of April corresponded with the growth stage  Feekes 8, last leaf just visible. As the crop moves beyond that point, catching up did not happen. Currently there is wheat out there in the state that has not hit hollow stem (Feekes 6) and there is wheat at Flag leaf (Feekes 9).

 

The Feekes Scale focused in on the stem extension growth phase. The period extends from hollow-stem (Feekes 6) to boot (Feekes 10).

The high rainfall totals we have could have also led to another deficiency sulfur. In the past S deficiency is fairly hard to find in Oklahoma. Our long history of low S using winter wheat and high sub-soil S levels have kept the response to Sulfur low, but not uncommon. Sulfur is a mobile nutrient and will also be lost via leaching especially in sandy soils in the northern part of the state. Sulfur deficient is different from N in that it shows in the newer growth as a general yellowing of crop. Kansas State has a lot of great resources on sulfur management in wheat.  https://webapp.agron.ksu.edu/agr_social/m_eu_article.throck?article_id=2132

https://bookstore.ksre.ksu.edu/pubs/MF2264.pdf

Sulfur deficiency in wheat. Photos by Dorivar Ruiz Diaz, K-State Research and Extension

If your wheat is yellow and before you call the fertilizer applicator, first confirm it is nitrogen and or sulfur and not something else. A key point to nitrogen deficiency is that the cholorsis will be worst on the oldest leafs while new growth is green. If N deficiency is confirmed then figure out how far along your wheat is. If the crop is around hollow stem to Feekes 8,  if you can get the N on soon there is a good chance to get your money back plus. Keep in mind with air temps above 60 degrees UAN will burn the tissue so it is best to use streamer nozzles, which will still burn but the tissue damage is lessened. If you do not have access to streamers you can dilute the UAN with water and use flat fan nozzles. Cutting the UAN with water reduce the impact of leaf burn, I typically recommend at least 2 part UAN to 1 part water, but a 1 to 1 is the safest.

Image of wheat with forage burn from UAN applied with streamer nozzles. Application was made two days prior with air temps where above 80 degrees.

If you have any questions or concerns please feel free to email any questions you may have.

Brian Arnall
b.arnall@okstate.edu

 

Results from 1st year of Soybean Starter Work

In the spring of 2014 we initiated what was to be the first year of a three year project evaluating starter fertilizers for soybean production in the southern Great Plains.  The first and second year was and is being funded by the Oklahoma Soybean Board.

Year one was a bit experimental in that with so many products on the market we needed some initial work to help focus the direction for years two and three.  I also added a treatment which I knew would have significant negative impact, for extension reasons.  Keep in mind two locations in a single year does not make an experiment nor provide enough information to draw a definite conclusion.   It is however enough to learn some lessons from and for us to plan for our 2015 trials.

The 2014 trial consisted of 12 treatments, Figure 1 and Figure 2.  In these treatments I wanted to see the impact of a standard practice, see if a specific nutrient may be more so beneficial, and evaluate a few popular products.  The spring of 2014 started out dry so at one of our two locations we pre-watered.  This was done by hauling water to the Lake Carl Blackwell (LCB) 1000 gallons at a time and pumping through sprinklers.  The other site, Perkins, we delayed planting until we had moisture.

Treatment Structure and rates for the 1st year of the Soybean Starter Study.

Treatment Structure and rates for the 1st year of the Soybean Starter Study.

List of fertilizers and products used.

List of fertilizers and products used.

Image taken while planting the Soybean Starter study at Perkins.  A CO2 system was used to deliver starter fertilizers with seed.

Image taken while planting the Soybean Starter study at Perkins. A CO2 system was used to deliver starter fertilizers with seed.

The two locations were also selected due to differences in soil fertility.  The LCB site is has good soil fertility, with exception of phosphorus (P), and the Perkins site pH was an issue.  I would have expected a benefit from adding P at both of these locations.  Figure 4 shows the soil test results.

Soil Test results from LCB and Perkins.

Soil Test results from LCB and Perkins.

At LCB as expected some of the treatments (Thio-Sul) reduced stand, some unexpectedly reduced stand (Fe) and others had less impact on stand (APP 5.0) than expected.  The growth at LCB was tremendous, the 30 in rows covered over very quickly and the majority of the treatments hit me waist high by early August (I am 6’0”).  Many of the treatments showed greater growth than check.  But when it comes down to it, grain pays and green does not.  Statistically there were no treatments that out preformed the un-treated check, however the K-Leaf and 9-18-9 did make 3 and 2 bpa more than the check respectively.  What I am hypothesizing at this site is that the added nutrients, especially those with high P levels, significantly increased vegetative grown and these big plants were delayed into going reproductive and they started setting pods later in much hotter weather.  While riding in the combine I could see that the plots with compact plants with clearly defined rows out yielded those were the vines had crossed over and we harvested through more of a solid mat of mature plants.  A hot August is not uncommon and I am curious on whether this trend repeats itself.  If it does this may direct us into research evaluating ways to force/promote the reproductive stage to start in these big plants.  Even if we can force flowering to start earlier, it’s unknown whether yields will increase or not.

Yield and Stand counts from the 2014 LCB Soybean Starter Study.

Yield and Stand counts from the 2014 LCB Soybean Starter Study.

The Check plot at LCB were plants noticeably a bit smaller and more yellow than the neighbors with phosphorus.

The Check plot at LCB were plants noticeably a bit smaller and more yellow than the neighbors with phosphorus.

Soybeans at LCB on August 4th.

Soybeans at LCB on August 4th.

The same trends in treatments reducing stand can be seen at Perkins, however the impact was less extreme.  Perkins being planted later due to waiting on moisture forced a later flowering date and I believe reduced overall yields.  But the addition of P at this low pH site definitely made a difference.  While again no treatments were statistically greater than the un-treated check the 2.5 gpa APP, DAP broadcast, APP/H2O, and Pro-Germ/H20 treatments increased yield by 5.6, 4.2, 3.8 and 1.7 bpa respectively.

Yield and Stand Counts from the Perkins 2014 Soybean Starter Study.

Yield and Stand Counts from the Perkins 2014 Soybean Starter Study.

Take home from year one was that at LCB the addition of a starter fertilizer had little benefit and if done wrong could cost you yield while at the low pH site of Perkins an addition 2.5 gallons of APP did get a 5 bpa bump, but do to variability in the trial the increase was not statistically significant.  This year we will drop some of the treatments and incorporate a few new treatments.   Based on the current weather we look to potentially being able to start with better soil moisture at planting.  Again do not take this work and significantly adjust any plans you have for your 2015 soybean crop. This is however some interesting findings that I wanted to share and make everyone aware of.  Finally thank you to the Oklahoma Soybean Board for providing funding for this work. www.oksoy.org/ 

 

 

Nitrogen Rich Strips

The Nitrogen Rich Strip, or N-Rich Strip, is a technique/tool/process that I spend a great deal of time working with and talking about.  It is one of the most simplistic forms of precision agriculture a producer can adopt.  The concept of the N-Rich strip is to have an area in the field that has more nitrogen (N) than the rest.  Due to our fertilizer applicators this is typically a strip.  The approach maybe somewhat new but at one point most producers have had N-Rich Strips in their fields, albeit accidentally.  Before the days of auto-steer it was not uncommon, and honestly still is not, to see a area in the field that the fertilizer applicator either doubled up on or skipped.  In our pastures and dual purpose/graze out wheat every spring we can see the tell-tale signs of livestock deposits.  When over laps or “Cow Pox” become visible we can assume the rest of the field is behind in nitrogen.  I like to tell producers that the goal of the N-Rich strip is to make a really big cow pie.

Cow Pox, Image courtesy Kaitlyn Nelson
Cow Pox, Image courtesy Kaitlyn Nelson

What I like most about the N-Rich Strip approach is its Simplicity.  The N-Rich Strip is applied and; Scenario 1. The N-Rich Strip becomes visible (Greener) you APPLY NITROGEN, Scenario 2.  The strip is not visible you Option A. DON’T APPLY NITROGEN Option B. Apply Nitrogen Anyways.  The conclusion to apply N or not is based on the reasoning that the only difference between the N-Rich Strip and the area 10 ft from it is nitrogen, so if the strip is greener the rest of the field needs nitrogen.  If there is no difference N is not limiting and our research shows N does not have to be applied.  However producers who decide to be risk adverse (in terms of yield) can apply N but it would be advised to do so at a reduce the rate.  Now is a good time to note that the N-Rich Strip alone provides a Yes or No, not rate recommendation.  At OSU we use the GreenSeeker optical sensor and Sensor Based Nitrogen Rate Calculator (SBNRC) to determine the rate, but that discussion will come later.  I equate the change from using yield goal N rate recs to the N-Rich Strip as to going from foam markers to light bars on a sprayer.   Not 100% accurate but a great improvement.

N-Rich Strip in no-till wheat near Hobart OK.

N-Rich Strip in no-till wheat near Hobart OK.

Now that we have covered the WHY, lets get down to the nuts and bolts HOW, WHEN, WHERE.

How the strip is applied has more to do with convenience and availability than anything else but there are a few criteria I suggest be met. The strip should be at least 10 ft wide and 300 ft long.  The rate should be no less than 50 lbs N (above the rest of the field) for grain only wheat and canola, 80 lbs N for dual purpose wheat.  The normal recommendation is that when applying pre-plant either have a second, higher rate programmed into the applicator or make a second pass over an area already fertilized. Many will choose to rent a pull type spreader with urea for a day, hitting each field.
Becoming more popular are applicators made or adapted for use.  ATV sprayers are the most common as they can be multi-purpose.   In most cases a 20-25 gallon tank with a 1 gpm pump is placed on the ATV with an 8-10ft breakover boom.  The third applicator is a ride away sprayer with a boom running along the rear of the trailer.  In all cases when liquid is the source I recommend some form of streamer nozzle.  In most cases there is not a great deal of thought put into what source.  I recommend whichever source is the easiest, cheapest, and most convenient to apply.

Vincent N-Rich Strip Applicator, Ponca City OK

Vincent N-Rich Strip Applicator, Ponca City OK

Ok State N-Rich Applicator

Oklahoma State Univ. N-Rich Strip Applicator

Gard N-Rich Strip Applicator, Fairview Ok

Gard N-Rich Strip Applicator, Fairview Ok

When the strip is applied in winter crops proper timing is regionally dependent. For the Central Great Plains, ideally the fertilizer should be applied pre-plant or soon after.  However,  in most cases as long as the fertilizer is down by the first of November everything works.  This does not say a strip applied after this time doesn’t work but it leaves more room for error.  There is a chance the crop could already be stressed or the nitrogen tied up and not release in time.  However when the N-Rich Strip approach is used on the Eastern Shore in Virginia and Maryland the strips have to be applied at green up.  The soils in that region are very deep sands and nitrogen applied in the fall may not make it to the spring.  Also most wheat producers in the area make three or more applications of nitrogen unlike the two (pre and top) of the Great Plains.  It is always important to make the tools fit your specific regional needs and practices and not the other way around.

Where is actually the biggest unknown.  The basic answer is to place the N-Rich Strip in the area that best represents the field.  Many people question this as it doesn’t account for spacial variability in the field, and they are correct.  But my response is that in this case spatial variability is not the goal, temporal variability is.  Keeping in mind the goal is to take a field which has been receiving a flat yield goal recommendation for the last 30+ years and make a better flat rate recommendation.  My typically request is that on a field with significant variability either apply a strip long enough to cross the zones or apply smaller strips in each significant area.  This allows for in-season decisions.  I have seen some make the choice to ignore the variability in the field, made evident by the strip, and apply one rate and others choose the address the variability by applying two or more rates.  One key to the placement of N-Rich Strips is record keeping.  Either via notes or GPS, record the location of every strip.  This allows for the strips to be easily located at non-response sites.  It is also recommended to move the strip each year to avoid overloading the area with N.  

I hear a great deal of talk about how it would take to much time to put out the N-Rich Strip.  However the majority of producers that do it once on one field, end up doing it every year on every field. There is very likely someone in your area who is using the N-Rich Strips.   As top-dress grows closer keep an eye out for a blog “Using the GreenSeeker Sensor and Sensor Based Nitrogen Rate Calculator”.

For more information on N-Rich Strips check out the YouTube video below, visit http://www.npk.okstate.edu or contact me directly at b.arnall@okstate.edu.  I have lots of material I am happy to share and distribute.

See the YouTube Video  http://www.youtube.com/watch?v=kJ3DSwWYgE8

Agriculture Apps for the IPad and IPhone

So I am going to approach a subject in this blog that is Not in my wheelhouse.  At the first of the year I was asked by a friend to speak on Ag Apps at the 2013 InfoAg meetings. His thought was, hey this guy teaches Precision Ag and uses a IPad, he must know apps. Well,  not so much.  From January to the day before the talk in July I spent a great deal of time scouring the App store and working, my wife described it as playing, on my IPad.  At info Ag I gave two talks, at the time of first talk on Tuesday I had 53 Free apps (1 paid), by the next morning and my second talk I had 60.
Since the meeting I have had numerous request for the slides and etc, so I thought this would be a good opportunity for a blog.  Since InfoAg (7.17.2013) I have picked up even more apps, the total is now 76.  However many of the new apps require registration.

On my IPad I have organized the apps into 8 basic folders:
ID Tools, Calculators, Seed, Sprayer/Chemical, Fertilizer, New/Weather/Markets, Scouting, Ag Apps  (apps I don’t know what to do with).

While I have 76 Apps I of course don’t use them all. What follows is basically my Editors Choice from each group. Please note I have not had the time to work with all 76 Apps. And I am by no means an expert in Apps or the use of them.
I do have a basic require of any App I use.  If I can not figure it out in 2 minutes its GONE.  An app should be intuitive, easy to use and have a purpose.  They only exception to the 2 minute rule is the Scouting Apps. Because of their complexity I allow them 5 minutes, then I am done.

ID Tools:
Image

This Category holds the One and Only App I paid for, Plant Images, a library of Nutrient Deficiency photos.  I mean I am a Soil Fertility guy.
I regularly use Plant Images, ID Weeds, and the Pestbook as references.  ID weeds is a true ID tool as you can use attributes to ID your weed, while the other two are visual reference tools.

Calculators:
Image

I personally use the two Nutrient Removal Apps the most, but after the latest update AG-PhDs Fert. Removal has become my favorite as it allows you to entire any yield level.
Harvest loss is also a handy App that lets you put $ to combine inefficiencies.

Seed:
Image
I do not use these often as I only do plot work, but I can see there usefulness in a operation.

Sprayer/Chemical:
Image

This group contains two of my first Ag Apps and most frequently used.
Being a fertilizer guy herbicides are not my forte however I use the often.
TankMixCalc and SpraySelect has been in my App arsenal from the beginning.
The nice item about many of the Sprayer Apps is the ability to save/store mixes or provide record keeping.

Fertilizer:
Image

Now the Fertilizer Apps are right up my alley.  But the only ones I use are the Cost Calcs.  As far as fertilizer recommendations go you must remember they are quite regionally specific so the Wisconsin Corn N rate Calculator does me little to no good.

New/Weather/Markets:
Image
This is the category that I have the most apps.  My first was Agriculture (DTN/PF), so I fall back to it often but I also like AgIndex and AgWeb. With the news/marketing ext apps the biggest key is find one that a) reports on topics of interest to you, they do differ and b) has a layout and design that is easy to use and enjoy.

Scouting
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The Scouting tools are a bit different, most but not all require registration of some kind.  I like most that I have tried but each has their own high and low points.  The use of a scouting tool will be highly dependent upon uses, goals, and what companies you currently work with.  For example Field Notes 360 has some nice points, you can make notes on photos, but you have to be a Pioneer employee or customer to get full use, I like Scout (Connected Farm) note taking capability and the fact you can input GreenSeeker NDVI values.  I have the beta version of Sirrus but I can all ready tell you it is shaking out to be my favorite. Two wins for Sirrus, its method of creating and editing boundaries is top notch but what I like the most is its ability to set up a direct grid sampling.

Ag Apps:

Image
This folder holds my Scientific Pub app the Web Soil Survey app, ArcGis app and the loan Ag game that snuck its way in with a official sounding name FarmGenius.

I don’t expect any app to change my life or yours, but it may make it easier.
The ID Tools, Calculators, Sprayer/Chem and Fertilizer apps are nice when I am in the field with a producer and just break out the IPad for easy demo/explanation.
There is a multitude of apps available and more being produced every day.  Just as everything else find what suites you regardless of others opinions.  When searching with an IPad remember to switch the search to include IPhone apps, there are some good ones out there that are IPhone only.
If you want to see my presentation from InfoAg, checkout their website www.infoag.org/program3 or go to the http://www.NPK.osktate.edu website and download the PDF of the slides under the Presentation tab.

Response to NPKS strips across Oklahoma

From the fall of 2011 to about a week ago one of my grad students, Lance Shepherd, has spent A LOT of time burning up the highways and back roads of Oklahoma.  Lance’s project was titled “NPKS Strips in Oklahoma winter wheat”, basically an extension of the N-Rich Strip concept.  We wanted to see if we could or would find a response to added nitrogen (N), phosphorus (P), potassium (K), or sulfur (S) fertilizer on top of the farmer’s fertilizer applications.  Over the two crop years lance applied NPKS strip on more than 80 fields from the Kansas border to the Red River.  Of those 80+ Lance was able to collect, by hand, grain samples from 59 sites.  Over the next few weeks I will be sharing some of the juicy tidbits we are gleaming from this fantastic data set.

NPKS applicator.  Gandy boxes hold each fertilizer and a pto driven fan blew the fertilizer down the boom.

NPKS applicator. Gandy boxes hold each fertilizer and a pto driven fan blew the fertilizer down the boom.

For the project at every site Lance collected soil samples to 18”, documented soil type and collected producer fertilizer, variety, and field history information.  Over the 59 locations there were essentially 236 trials.  The yield of each strip (N,P,K, and S) was compared back to a sample collected from the field, referred to as Farmer Practice. Of the 236 comparisons there were a total of 17 positive responses.  Of these 17 responses seven were to N, seven to P, three to K, with no responses to S.

N-Rich strip very evident in field west of Alva.  N-Rich 70 bu/ac Farmer Practice 38 bu/ac.

N-Rich strip very evident in field west of Alva. N-Rich 70 bu/ac Farmer Practice 38 bu/ac.

We are learning a great deal from these 17 locations.  The biggest take home was that in most instances soil test results identified the yield limiting factors.  For example of the seven responsive P locations six had either a low soil pH or low soil P index, some both.  At only one site was there a response not predicted by soil test.  Of all 59 harvested fields more than just six had low P or pH levels however most producers had applied enough fertilizer to reach maximum yield. For nitrogen two items proved to be the most likely reason for loss of yield, under estimated yield goal or environment conducive to N loss.  As for the K responses we look at both K and chloride (Cl) as KCl, 0-0-62 potash, was applied in the K strip.  Just looking at the soils data K was not low at any of the three sites.  However, two sites are in sandy loam soils, which is conducive to Cl deficiencies.  The lack of response to S was not surprising as soil tests indicated S was sufficient at all 80 locations were strips were applied.  So again what did we learn from these plots, soil testing is key in maximizing yield and profitability and in most of the N responsive sites the N-Rich strip indicated a need for added fertilizer in February.

Placing Fertilizer with Canola at planting has positives and negatives.

With all things holding constant the last canola trials of our project should be picked up by the plot combine Thursday 6-20-13.  Before the first yield results comes to my desk I can tell you that we are learning a great deal from the trials this year.  In particular the DAP (18-46-0) placed with seed trail that was supported by the Oklahoma Oilseed Commission.  This past year at the no-till site in Perkins, which has a low soil pH, the check plots that did not receive any fertilizer, preplant or banded, did not survive the winter.   Additionally at both of our locations, Lahoma (low soil test P) and Perkins, we have documented that oil content was reduced when phosphorus was left out of the treatment.

Additionally out of the four site years, that is two locations over two years, the addition of DAP with the seed in-row reduced stand.  The graph below shows just how much stand was reduced on a relative basis. Relative stand is a way to compare the DAP treated to the Check (no DAP) which we assume is 100%.  So if we look at the graph below the plots were at 75% relative stand (i.e. 25% loss) at approx 5 lbs N per ac.  By about 15 lbs N the stand was down to 50%.

There are a few things to keep in mind first, in the case of these trials stand loss did not always mean yield loss.  Canola is a great compensatory crop, if there is open space it will grow into it.  I will have to run the final yield data to get more answers.  These trials were planted on 15″ rows putting down 5 lbs seed per ac, or at least that was the target rate.  Many have shown that the seeding rate does not have to be that high if sown properly.  I believe in a few cases we may have actually benefited from thinning the stand.  However if you were planting 2.5 lbs seed per acre a small loss of stand may be a bigger yield loss.  This is one of the question we will have to answer in the future.

And finally it should be noted that canola is planted on a wide range of spaces 6″,7.5″, 12″, 15″, 30″ are some of the most common.  As the row width changes the amount of N placed with the seed changes.  In other words if the goal is 50 lbs DAP per acre  you will put twice as much in a 15″ row than you do a 7.5″ row.  The Table at the bottom provide a guide for equivalent rate based on 15″ rows.  For example if your target a excepted stand loss of 25% (5 lbs N according to the Figure) but you are planting on 6″ row spacing the recommendation would be apply no more than 13 lbs N per ac in the row or 72 lbs DAP/ac (13/.18)

Impact of DAP (18-46-0) placed in-row on canola stand in terms of lbs N ac-1.

Impact of DAP (18-46-0) placed in-row on canola stand in terms of lbs N ac-1.

Equivalent amount of N based on 15" row spacing.

Equivalent amount of N based on 15″ row spacing.