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Using the GreenSeeker after Freeze Damage
After discussions with producers in southern Kansas I felt the need to bring back this past blog. It seems that much of (not all) the early planted wheat lost a significant amount of biomass during the winter and the N-Rich Strip GreenSeeker approach is producing what looks to be low yield potentials and N-Rate recommendations. This should be treated much like we do grazed wheat and the planting date should be adjusted, see below. It is also important to note that in the past year a new wheat calculator was added to the NUE Site. http://nue.okstate.edu/SBNRC/mesonet.php. Number 1 is the original OSU SBNRC but the #2 is calculator produced by a KSU/OSU cooperative project. This is the SBNRC I recommend for use in Kansas and much of the norther tier of counties in OK.
Original Blog on Freeze Damage and the GreenSeeker.
Dr. Jeff Edwards “OSUWheat” wrote about winter wheat freeze injury in a receive blog on World of Wheat, http://osuwheat.com/2013/12/19/freeze-injury/. As Dr. Edwards notes injury at this stage rarely impact yield, therefore the fertility requirements of the crop has not significantly changed. What will be impacted is how the N-Rich Strip and GreenSeeker™ sensor will be used. This not suggesting abandoning the technology in fact time has shown it can be just as accurate after tissue damage. It should be noted GreenSeeker™ NDVI readings should not be collected on a field that has recently been damaged.
A producer using the N-Rich Strip, GreenSeeker™, Sensor Based N-Rate Calculator approach on a field with freeze damage will need to consider a few points. First there need to be a recovery period after significant tissue damage; this may be one to two weeks of good growth. Sense areas that have had the same degree of damage as elevation and landscape position often impacts the level of damage. It would be misleading to sense a area in the N-Rich strip that was not significantly damaged but an area in the Farmer Practice that took a great deal of tissue loss.
Finally we must consider how the SBNRC, available online at http://nue.okstate.edu/SBNRC/mesonet.php, works. The calculator uses NDVI to estimate wheat biomass, which is directly related to grain yield. This predicted grain yield is then used to calculate nitrogen (N) rate. So if biomass is reduced, yield potential is reduced and N rate reduced. The same issue is seen in dual purpose whet production. So the approach that I recommend for the dual purpose guys is the same that I will recommend for those who experienced significant freeze damage. This should not be used for wheat with just minimal tip burn.
To account for the loss of biomass, but not yield, planting date needs to be adjusted to “trick” the calculator into thinking the crop is younger and has greater potential. Planting date should be move forward 7 or 14 days dependent For example the first screen shot shows what the SBNRC would recommend using the real planting date. In this case the potential yield is significantly underestimated.
The second and third screen shots show the impact of moving the planting date forward by 7 and 14 days respectively. Note the increase in yield potential, which is the agronomically correct potential for field considering soil and plant condition, and increase in recommended N-rate recommendation. Adjust the planting date, within the 7 to 14 day window, so that the yield potential YPN is at a level suitable to the field the yield condition and environment. The number of days adjusted is related to the size and amount of loss. The larger the wheat and or greater the biomass loss the further forward the planting date should be moved. In the example below YPN goes from 37 bu ac on the true planting date to 45 bu ac with a 14 day correction. The N-rate changes from 31 lbs to 38 lbs, this change may not be as much as you might expect. That is because YP0, yield without additional N, also increases from 26 to 32 bushel.
Image 1. Planting date 9/1/2013. YPN 37 bu ac-1 and N-Rec 31 lbs ac-1.
Image 2. Planting date 9/8/2013. YPN 40 bu ac-1 and N-Rec 34 lbs ac-1.
Image 3. Planting date 9/15/2013. YPN 45 bu ac-1 and N-Rec 38 lbs ac-1.
This adjustment is only to be made when tissue has been lost or removed, not when you disagree with the yield potential. If you have any questions about N-Rich Strips, the GreenSeeker™, or the online SBNRC please feel free to contact me at b.arnall@okstate.edu or 405.744.1722.
The Sufficiency versus Replacement tipping point.
Being educated in the realm of Soil Fertility at Oklahoma State University by the likes of Dr Gordon Johnson and Dr. Bill Raun, Brays Nutrient Mobility Concept and Mitscherlich’s Percent Sufficiency Concept are ingrained in my psyche. In class the concept of Build and Maintain for phosphorus fertilizer management was just briefly visited and not discussed as a viable option. For anyone in the corn belt, and some Okies, reading this that may seem unusual. But when I was in school on average in Oklahoma there was about 100-200 K acres of 100 120 bpa (bushel per acre) corn, 300-400 K acres of 40-50 bpa sorghum, and over 5 million acres of 20-30 bpa wheat. In a state with those average yields, replacing P removed by the crop was not a major concern.
But times are changing. There is more corn and soybean planted and the achievable yields of all crop are increasing. While the average winter wheat producer should not be worried about replacement rates of P there is a growing group of producers that should. This blog will discuss the scenarios in which sufficiency rates are best and those in which replacement should be considered. The OSU factsheet PSS-2266 goes in-depth on each of these methods.
Applying P based on sufficiency will increase soil test P levels in a low yielding environment. For example on a 20 bpa wheat field that starts out with a soil test P level of 0. Using the sufficiency recommendation each year the soil test value will reach 20 ppm (40 STP) in 20 years. A 30 bpa field would take 30 years. Yes that is a long time but the soil test value is increasing a little each year. The point of 20 ppm is important because at that level the crop is 95% sufficient, meaning if no P is added the crop will only reach 95% of the fields yield potential.
Using a mass balance approach we can determine at what point does the crop remove more than we can supply with in or near furrow starter fertilizer. Table 1 shows the values I am using for the discussion. The first column is just the average amount of P removed per bushel of grain, most of our grains fall in the .4 to .5 lbs P per bushel range. The second column is the soil test value at which P level is said to be at 90% sufficient. The reason this column is included is that the P2O5 reccomendation for this P level fits into the starter rate for all crops. The low high starter rates are the typical range of P2O5 that is delivered within the safe range (N based) and what I see as the common rates. These values may be above or below what you use.
Table 1. Values used to create Table 2. Phosphorus per bushel of grain. Mehlich 3 soil test value (ppm) at which crop is determined to be 90% sufficient, typical range of P2O5 applied with starter fertilizers, recommended P2O5 rate when soil test P is at 90% sufficiency.
Table 2 is pretty simple but it is the center point of this article. The one caveat I need to add is this assumes strip till or 2*2 / 3*2 is not being used. Table 2 is using the starter range and removal value to determine the yield level the starter can support. The first take on this table may provide some hint on why in a state with 5 million acres of wheat averaging 36 BPA the state soil fertility specialist didn’t focus on replacement rates. In fact for most for most the the wheat ground P application is higher than removal and P levels are slowly increasing. The big take home from this table should be is my yield level outside this window? If so do not immediately go out in crease your P rates but do take a close look at your system as a whole. Take a close look at your cropping system, not just one seasons but look at a three or four year cycle. Add up P applied and P removed, are you positive or negative net balance? If you are negative take a long hard look at your soil test over time. Some soils can supply a large amount of P even if you are removing more than you apply. Other soils will be rapidly drawn down. Regualr soil testing allows for producers to keep an eye on these values.
Table 2. Yield level (bushels per acre) at which P removal is equal to P added in starter fertilizer application.
In the end even if the production warrants the use of replacement rates, the current market may not. For more on that read https://osunpk.com/2016/08/27/now-may-not-be-the-time-for-replacement/.
Speaking of market currently both soybeans and cotton are getting a lot of attention due to how the economics is penciling out. Soybean is a “heavy” P crop pulls .8 lbs per bpa while cotton removes 13 lbs per bales. Both of these crops are salt sensitive and the rate of inforrow is typically quite low providing only about 6 lbs when on 30″ rows. If you are growing beans or cotton make sure you account for their removal when you talley up your system.
Below is a table that I wanted to add, well because I like it. This table illustrates that buildup, and drawdown, rate is heavily impacted by existing soil test value. In short it takes a lot more fertilizer P to raise soil test p levels in a very low P testing field than it does when soil test P is closer to optimum, 19 lbs per 1 lb at STP of 10 and 5 lbs per lb when STP is 65. The exact rate changes by soil type and the same holds true to drawn down via crop removal.
Amount of P2O5 above crop removal needed to increase soil test phosphorous based upon initial soil test results.
Adapted From http://www.spectrumanalytic.com/support/library/ff/Soil_test_P_and_K_buildup_and_drawdown.htm “Drawdown of Soil Test Phosphorus and Potassium Levels by Alfalfa, K.L. Wells & J.E. Dollarhide, Univ. of Kentucky, Soil Science News & Views, Vol. 21, No. 3, 2000”
Any questions or comments? Feel free to contact me at b.arnall@okstate.edu
Planting Wheat After Anhydrous
Every year in August and early September I get the question “How soon after applying NH3 can I sow wheat?”. Typically my answer has been a conservative one which takes into account rate, depth, spacing and soil moisture to end up with a range of 3 days to a week. The concern with anhydrous application is that when NH3 is placed in the soil it immediately turns into NH4 by striping H from H2O. This action releases OH into the soil in increases pH, depending on rate pH can reach 10.0 this hike in soil pH is a short term as the system disperrses and NH4 immediately begins the conversion to NO3 release H and driving down pH. The high pH in itself is not the problem but if the pH is still high and soil dries the OH will strip H from NH4 and NH3 is formed. The ammonia gas (NH3) is what can easily damage the sensitive seedling.
After fielding several calls in one day I wanted to dig a bit deeper and see what the science and specialist say. I was hoping for a nice consensus, haven’t found that yet. Here are some snip-its.
From Kansas State University
Dr. Dave Mengel
As a general rule, wait about 7 to 10 days between the anhydrous ammonia application and wheat planting. The higher the nitrogen rates and the wider the spacing (creating a higher concentration of ammonia in the band), the longer period of time you should wait. Also, in dry soils you may need to wait longer.
Canada Grains Council’s Complete Guide to Wheat Management Link
In the past, it was recommended that seeding be delayed for two days after banding anhydrous ammonia (NH3). However, in many soils as long as the NH3 is placed 5- 7.5 cm ( 2-3 inches) away from the seed, NH3 can be applied at the time of seeding. Seed damage from NH3 is most likely to occur under dry conditions on sandy soils when there is insufficient separation from the seed. Placement of fertilizer nitrogen should be deeper in sandy soils than in loams or heavy textured soils. Narrow band spacing 25 to 30 cm (10-12 in) is better than wider band spacing particularly under low moisture conditions.
From University on Minnesota
Peer reviewed publication
VARVEL: EFFECTS OF ANHYDROUS AMMONIA ON WHEAT AND BARLEY AGRONOMY JOURNAL, VOL. 74. NOVEMBER-DECEMBER 1982
Field experiments were conducted 1979-1981 on a Wheatville loam soil. The treatments consisted of three rates of N as anhydrous ammonia (45, 90, and 135 kg/ha) in 1979 and four rates of N (0, 45, 90, and 135 kg/ ha) in 1980-1981 at three depths (8,16, and 24 cm) in all combinations. Spring wheat and barley were then seeded at three different times. Seedling stand counts, grain yield, and protein were used to determine the effect of the treatments. Seedling stands were reduced in some cases, but no reduction in grain yield or protein was obtained due to the reduction in stand. The most important factor in spring anhydrous application was the depth of application, which caused greater moisture loss and seedbed disruption at the 24-cm application depth.
Spring wheat and barley response to N rates was similar at all depths of application (no significant interaction between N rate and application depth). The results indicate that anhydrous ammonia can be applied safely at planting time on spring wheat and barley, if applied at the 8 to 16 cm depth and at N rates currently used in the northern Great Plains.
From University on Minnesota (referring to corn) link
The only risk of planting soon after AA application is if seeds fall within the ammonia retention zone. To avoid seedling injury separation in time or space can be important. Under ideal soil moisture conditions and proper application depth of a typical agronomic rate normally there is little risk of seedling injury even if planted on top of the application zone right after AA application. That said, this can be risky and I would not recommend planting on top of the AA row. If you have RTK guidance it is very easy to apply AA between the future corn rows. If RTK guidance is not an option, I would recommend applying AA on an angle to the direction of planting to minimize the potential for planting on top of the AA band. If application conditions are less than ideal and you have no RTK guidance to ensure a safe distance from the AA band, then waiting 3 to 5 days before planting is typically enough time to reduce the risk of seedling injury.
From University on Wisconsin (referring to corn) Link
The depth of NH3 placement was the greatest factor in determined potential seedling damage. The time after application had little impact.
Iowa State University (referring to corn)
by Regis Voss, extension agronomist, Department of Agronomy
The wet fall and spring will cause anhydrous ammonia application and corn planting date to be close. This will lead to the oft asked question, “How long do I have to wait to plant corn after ammonia application?” If there is a soil separation between the ammonia zone and the seed, planting can be done the same day the ammonia is applied. If the seed is to be placed in the ammonia zone, the longer the waiting period the less potential for root injury. There is no magic number of days to wait.
WAKO NH3 applicator used for in-season application.
My take home from several hours of reading research articles and factsheets was my favorite answer IT DEPENDS. I believe Regis Voss with ISU had it right, there is no magic number. The important aspects for determining time will be 1) Soil Moisture 2) N rate 3) Depth and 4) shank spacing. From the reading I think there may be some general rules of thumb.
On the conservative side with good soil moisture, NH3 placed at 6″ deep, rate below 80 lbs and spacing of about 15″ the next day should be ok. As any one of these factors change (drier soil, higher rates, shallower application, wider rows) the more time should be added to reduce risk. One thing to consider is field variability. While the field on average may have great moisture there could be dry spots, while on average you are 6″ deep with the NH3 there are areas the rig is bound to rise up and go shallow. So there is always a chance for hot spots. All of that said I could not find any research on this topic for winter wheat in the southern Great Plains much less Oklahoma. I will always tend to the safe side and suggest if possible to delay sowing a few days after applying anhydrous. However if time is critical proceed with caution.
Looks like I can add one more project to my list and I need to find some open ground and do some “Experimenting”.
Happy Sowing All!
Now may not be the time for Replacement
For phosphorus (P) and potassium (K) fertilizer management there are three primary schools of thought when it comes to rate recommendations. The three approaches are Build-up, Maintenance/Replacement, and Sufficiency. There is a time and place for each one of the methods however the current markets are making the decision for the 2016-16 winter wheat crop a very easy one. The OSU factsheet PSS-2266 goes in-depth on each of these methods. For the rest of the blog I will use P in the conversation but in many scenarios K should/could be treated the same.
Build-up is when soil test is below a significant amount of fertilizer, about 7.5 lbs P2O5 per 1 ppm increase, is added so that soil test values increase. This method is only suggested when grain price is high and fertilizer is relatively cheap. Given the market, this is a no go. The two most commonly used methods of recommendation are Replacement and Sufficiency. In the replacement approach if the soil is at or below optimum P2O5 rate it based upon replacing what the crop will remove. The sufficiency approach uses response curves to determine the rate of P that will maximize yield. These two values are typically quite different. A good way you boil the two down is that replacement feeds the soil and sufficiency feeds the plant.
Oklahoma State Universities Soil, Water, and Forage Analytical Lab (SWFAL) provides recommendations utilizing sufficiency only while many private labs and consultants use replacement or a blended approach. Some of this is due to region. Throughout the corn belt many lease agreement contain clauses that the soil test values should not decrease otherwise the renter pays for replacement after the lease is over. For the corn belt both corn and soybean can be expected to remove 80 to 100 pounds of P per year. Conversely the Oklahoma state average wheat crop removes 17 lbs P a year. In areas where wheat yields are below 40 bushel per acre (bpa) using the sufficiency approach for P recs can increase soil test P over time.
This conceptual soil test response curve is divided into categories that correspond with below opti-mum, optimum and above optimum soil test values. The critical level is the soil test level, below which a crop response to a nutrient application may be expected, and above which no crop response is expected. At very high soil test levels crop yield may decrease.
*Rutgers Cooperative Extension Service FS719
Back to subject of this blog, consultants, agronomist, and producers need to take a good look at the way P recs are being made this year. Profitability and staying in the black is the number 1, 2, and 3 topic being discussed right now. The simple fact is there is no economic benefit to apply rate above crop need, regardless of yield level. The figures above demonstrate both the yield response to fertilizer based upon soil test. At the point of Critical level crop response / increase in yield is zero. What should also be understood is that in the replacement approach P fertilizer is still added even when soil test is in Optimum level. This also referred to as maintenance, or maintaining the current level of fertility by replacing removal. If your program is a replacement program this is not a recommendation to drop it completely. Over a period of time of high removal soil test P levels can and will be drawn down. But one year or even two years of fertilizing 100 bpa wheat based on sufficiency will not drop soil test levels. On average soils contain between 400 and 6000 pounds of total phosphorus which in the soil in three over arching forms plant available, labile, and fixed. Plant available is well plant available and fixed is non plant available. The labile form is intermediate form of P. When P is labile it can be easily converted to plant available or fixed. When a plant takes up P the system will convert labile P into available P. When we apply P fertilizer the greatest majority of was is applied makes it to the labile and fixed forms in a relatively short period of time. For more in-depth information on P in the soil you can visit the SOIL 4234 Soil Fertility course and watch recorded lectures Fall 2015 10 26-30 Link .
How to tell if your P recs have a replacement factor, not including calling your agronomist. First replacement recs are based on yield goal, so if you change your yield goal your rate will change. The other and easier way is to compare your rates to the table below. Most of the regional Land Grant Universities have very similar sufficiency recs for wheat. Another aspect of the sufficiency approach is the percent sufficiency value itself. The sufficiency can provide one more layer in the decision making process for those who are near the critical or 100% level. Response and likelihood of response to P is not equal. At the lowest levels the likelihood of response is very high and the yield increase per unit of fertilizer is the greatest. As soil test values near critical (32.5 ppm or 65 STP) the likelihood of response and amount of yield increase due to fertilizer P decreases significantly. At a STP of 10 the crop will only produce 70% of its environmental potential if P is not added while at a STP of 40 the crop will make 90% of its potential. The combination of % sufficiency and yield goal can be used to determine economic value of added P.
*From Oklahoma State University Soil Test Interpretations. Fact Sheet PSS-2225
*Based on Mehlich 3
*PPM (parts per million) is used by most labs
*STP (soil test P) is a conversion used by some Universities. Equivalent to pounds per acre.
* for a 0-6” in soil sample PPM * 2 = STP.
This data is available from OSU in multiple forms from the Factsheet PSS-2225, the SWFAL website, Pete Sheets quick cards, and the Field Guide App.
This year with margins tight soil testing is more important than ever before. Knowing the likelihood of response and appropriate amount of fertilizer to apply will be critical maximizing the return on fertilizer invest while maximizing the quality and amount of grain we can produce. Visit with your consultant or agronomist to discuss what the best approach is for your operation. Lets ride this market out, get the most out of every input and come out of this down cycle strong.
Feel free to contact me with any questions you may have.
Brian
b.arnall@okstate.edu
2015-16 Wheat Crop Nitrogen Review
From trials to phone calls (and text messages, and tweets, and ect. ect) I have gathered a fairly good picture of this years winter wheat nitrogen story. And as normal, nothing was normal. Overall I seen/heard three distinct trends 1) Did not take much to make a lot 2) took a ton to make a lot 3) saw a response (N-rich strip or cow-pow) but fertilizer never kicked in. Covers most of the options, doesn’t it.
The N-rich strips really came out over all very good this year. N-Rich Strip Blog. On average many of those using the N-Rich Strip and SBNRC (SBNRC Blog) producers have been getting in the neighborhood of 1.0-1.3 lbs of N applied per bushel produced. This year the numbers ran from 0.66 to 2.3 lbs of N per bushel. In both extremes I believe it can be explained via the field history and the N-Cycle.
Nitrogen Cycle Pete’s Sheet
In at least two fields, documented with calibrated yield monitors, the N-Rich Strip and SBNRC lead to massive yields on limited N. One quarter of IBA bumped 86 bpa average on 47 lbs of N while a second quarter, also IBA, managed 94 bpa average on about 52 units of N. We are currently running grain samples from these fields to look protein levels.
The other side of the boat were those with N-Rich strip calling for +2.0 lbs N per bushel. I had received notes from producers without N-rich strips saying that they could predict yield based on the amount of N applied and it was a 2 to 1 ratio. Not always but many of these high N demand fields where wheat following a summer or double crop or corn or sorghum. While many of the low N demand fields were wheat after wheat or wheat after canola. In a rotational study that had been first implemented in the 2014-15 crop year I saw big differences due to previous crop. The picture below was taken in early March. The straw residue in wheat after wheat had just sucked up the nitrogen. While it was evident the residue from the canola broke down at a much more rapid pace releasing any and all residual nutrients early.
The yield differences were striking. The canola rotation benefited the un-fertilized plots by 22 bpa and even with 90 lbs of N applied having canola in the rotation increased yields by 12 bpa. We are looking and grain quality and residual soil sample now. I am sure there will be a more indepth blog to follow.
Canola Wheat Rotation study year two yield average. yields average across previous years N-rates.
Another BIG story from the 2015-16 wheat crop was the lack of benefit from any N applied pre-plant. It really took top-dress N this year to make a crop. Due to our wet early fall and prolong cold winter N applied pre was either lost or tied up late. Work by Dr. Ruans Soil Fertility Program really documented the lack luster pre-plant N effect. The figure below shows 4 location of a rate by timing student. The number at the bottom of each graph is a rate by time (30/0 means 30 lbs Pre-0 lbs Top, 60/30 means 60 lbs Pre-30 lbs Top). At every single location 0/60 beat 60/0. Top-dress N was better than Pre-plant N.
Figure 1. Work from Ethan Driver and Dr. Bill Raun. Study looked at rate and timing of N fertilization in wheat. Treatments are ordered by total N applied.
The last observation was lack of response from applied N even though the crop was deficient. Seen this in both the NE and NW corners. I would hazard with most of the circumstance it was due to a tie up of applied N by the previous crops residue. The length at which the winter stretched into spring residue break down was also delayed.
Take Home
Here it is folks APPLY NITROGEN RICH STRIPS. Just do it, 18 years of research preformed in Oklahoma on winter wheat says it works. Hold off on heavy pre-plant N even if anhydrous is cheap. It does matter how cheap it is if it doesn’t make it to the crop. Will we see another year like 2015-16, do not know and not willing to place money on either side. What we do know is in Oklahoma split applying nitrogen allows you to take weather into account and the N-Rich strip pays dividends.
There are several fact sheets available on top-dressing N and the application of N-Rich strips. Contact your local Oklahoma Cooperative Extension Service county educator to get a copy and see if they have a GreenSeeker sensor on hand.
DAP vs MAP, Source may matter!
Historically the two primary sources of phosphorus have had different homes in Oklahoma. In general terms MAP (11-52-0) sales was focused in Panhandle and south west, while DAP (18-46-0) dominated the central plains. Now I see the availability of MAP is increasing in central Oklahoma. For many this is great, with MAP more P can be applied with less material. which can over all reduce the cost per acre. There is a significant amount of good research that documents that source of phosphorus seldom matters. However this said, there is a fairly large subset of the area that needs to watch what they buy and where they apply it.
If you are operating under optimum soil conditions the research shows time and time again source does not matter especially for a starter. In a recent study just completed by OSU multiple sources (dry, liquid, ortho, poly ect ect) of P were evaluated. Regardless of source there was no significant difference in yield. With the exception of the low pH site. The reason DAP was so predominate in central Ok, soil acidity. See an older blog on Banding P in acidic soils.
Figure 1. The cover of an extension brochure distributed in Oklahoma during the 1980s.
When DAP is applied, the soil solution pH surrounding the granule will be alkaline with a pH of 7.8-8.2. This is a two fold win on soil acidity aka aluminum (Al) toxicity. The increase in pH around the prill reduces Al content and extends the life of P, and as the pH comes back down the P ties up Al and allows the plant to keep going. However, the initial pH around the MAP granule ranges from an acid pH of 3.5-4.2. There is short term pH change in the opposite direction of DAP, however the the Al right around the prill becomes more available and in theory ties up P even faster.
Below is a table showing the yield, relative to untreated check, of in-furrow DAP and MAP treatments in winter wheat. The N401 location had a ph 6.1 while Perk (green) has a pH of 4.8. At Perkins in the low pH, both forms of P significantly increased yeild, almost 20 bushel on the average. DAP however was 5 bushel per acre better than MAP. At the N40 site the yield difference between the two sources was 1 bushel.
Relative yield winter wheat grain yield MAP and DAP both applied at equal rates of P (32 lbs P2O5 ac) when compared to a untreated check.
In general it can be said that in acid soils DAP will out preform MAP while in calcareous high pH soils MAP can out preform DAP. So regarding the earlier statement about the traditional sales area of MAP or DAP if you look at the soil pH of samples went into the Oklahoma State University Soil, Water, and Forage Analytical lab the distribution makes since.
Average soil pH of samples sent into OSU soil water forage analytical lab by county.
In the end game price point and accessibility drives the system. In soils with adequate soil pH levels, from about 5.7 to around 7.0, get the source which is cheapest per lbs of nutrient delivered and easiest to work with. But if you are banding phosphorus in row with your wheat crop because you have soil acidity, DAP should be your primary source.
Wheat Disease Update – 14 May 2016
Wheat Disease Update – 14 May 2016
Bob Hunger, Extension Wheat Pathologist
Department of Entomology & Plant Pathology – 127 Noble Research Center – Oklahoma State University – Stillwater, OK
405-744-9958 (work) – bob.hunger@okstate.edu
This past week in addition to being around Stillwater, I attended field days in Canadian County (just west of Oklahoma City), Kay County (north of Ponca City), Kingfisher County (northwest of Oklahoma City) and Major County (west of Enid). Wheat I examined ranged from milk to medium dough. Some active stripe rust (producing spores) was still present in Major County, but only at low levels. Leaf rust is prevalent around Stillwater, with low levels of leaf rust found in Kay and Major Counties.
Symptoms of barley yellow dwarf (BYD) also were observed at all locations. As previously indicated, I observed only discolored (yellow to reddish-purple) flag leaves and no stunting indicating infection of BYDV by aphids occurred in the spring. One observation of note is that often with BYD the flag leaf will be discolored but leaves below the flag remain green as in the photo below. This is indeed BYD.
Wheat tiller showing flag leaf with BYD symptoms but lower leaf green
The Diagnostic lab also has continued to receive samples testing positive for Wheat streak mosaic virus and/or High plains virus. These samples have been from northern, northwestern and the panhandle regions of Oklahoma. For more information, see Fact Sheet EPP-7328 (Wheat Streak Mosaic, High Plains Disease, and Triticum Mosaic: Three Virus Diseases of Wheat in Oklahoma) at http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-8987/EPP-7328.pdf
Finally, another disease that is making an appearance in Oklahoma this year is take-all. I have not observed take-all in Oklahoma now for many years; in fact, the last time we received a number of samples of take-all was back in the early 2000s. Take-all is favored by moist conditions and a neutral to alkaline soil pH. Abundant moisture starting a year ago and in areas of Oklahoma again this year have likely provided conditions favorable for this disease in a few areas. Take-all will first show as white plants in low-lying, wet areas after a period of hot days. I don’t think this will be a significant disease in Oklahoma this year, but wanted to bring it to your attention.
Darkened crown and roots due to take-all
Reports/excerpts of reports from other states:
Colorado: Dr. Kirk Broders (Plant Pathologist); Colorado State University; Fort Collins, CO; May 11, 2016: “There has been good precipitation around the state this spring which has led to a good wheat crop, but also provides the potential for more foliar diseases than we usually see. Most of the wheat in the southeast has already headed out and there are low levels of stripe rust present, but likely will not impact yield especially where the wheat is further along. Wheat in the rest of the state ranges from booting to heading (Feekes 10 – 10.1). It is at this point that the flag leaf will also become fully emerged, and it will be important to ensure the flag leaf is protected in order to protect yield. I have received reports of stripe rust from multiple locations in eastern Colorado from Prowers County in the southeast and further north in Cheyenne, Kit Carson, Yuma, Washington and Arapahoe counties. Scott Haley mentioned he saw bacterial streak in the northeast part of Colorado and I have also received a couple reports and confirmed one report of Stagonosopora blotch on wheat in Washington County. Both reports were from wheat planted after a previous wheat crop. There were several reports of Stagonospora blotch in the state last year likely due to the significant amount of precipitation. This fungus is capable of surviving on wheat stubble and then infecting the successive crop given ample rainfall. Both Stagonospora blotch and stripe rust remain sporadically distributed and at low levels in most regions in the state, but with more predicted rain in the forecast growers may want to consider applying a fungicide once the flag leaf is fully emerged in order to ensure it is protected and the head is able to yield to potential. Certainly, they should take into consideration whether there is any foliar disease currently in the field or in their region, the potential yield of the crop and the cost of the fungicide to be applied, as well as the probability of cool, rainy weather in the forecast.”
Wisconsin: Dr. Damon Smith (Ast Prof – Field Crops Pathology); University of Wisconsin-Madison; May 11, 2016: “It was only a matter of time…. Today we confirmed the first observations of stripe rust in Wisconsin for 2016. Brian Mueller, Graduate Research Assistant in the Field Crops Pathology Lab at the University of Wisconsin-Madison found active stripe rust pustules in winter wheat in both southern and south central Wisconsin. In southern Wisconsin stripe rust was found in the Wisconsin Winter Wheat variety trial located in Sharon, Wisconsin. Stripe rust was at low incidence and severity on emerging flag leaves with some lesions manifesting as chlorotic flecks and not yet active. We speculate that the epidemic initiated recently. With the humid and rainy weather over the past several days, conditions have been ripe for symptom development. The second stripe rust confirmation was at the Arlington Agricultural Research Station in an integrated management trial for stripe rust. Again, incidence and severity were low on emerging leaves, therefore, we speculate that the epidemic has recently initiated. We have been actively looking for stripe rust as there have been numerous reports of epidemics in winter wheat in states to our south and west. Given the recent weather patterns we will likely see more stripe rust show up in the state. I suspect we will start to see fungicide sprayers active in wheat fields in the state given the fact that the epidemic onset is coinciding with the emergence of flag leaves. We will continue to monitor the situation carefully.”
Planting considerations after hayed or failed wheat crop
This article is written by Dr. Josh Lofton
Oklahoma State University Cropping Systems Extension Specialist
Determining wheat yield loss:
The question on to how to manage wheat production that has suffered high potential yield loss can be quite challenging. High disease pressure and periods of dry conditions have been the main focus of this season’s wheat crop, but the recent storms have added to these issues with fields having >50% lodged wheat. While this may be a great concern when viewing this crop initially, a lodged or damaged wheat crop may still have decent yield potential. It is important to remember that, 50% lodging does not necessarily represent 50% yield loss. Many times the wheat crop will stand back up days or weeks after a lodging event. Overall, for a questionable stand of wheat, the best course of action might be to keep the stand and get the most yield possible from the crop. If you are considering planting a crop after failed or abandoned wheat, there are some important considerations before making the jump.
Insurance potential for a replacement crop
This will be the biggest catch for terminating a current wheat crop for a replacement summer crop. In many scenarios, once the wheat crop has begun to head this will be considered a double crop situation. In this instance many companies will not allow insurance to cover the following crop. Even if insurance is available for this double-crop scenario, at least three year yield potential numbers are frequently the minimum needed to receive this support. The best first steps for a grower to take when evaluating their fields planting of a replacement crop after a termination or hay is to check on their individual coverage and talk to their representatives before any action is taken.
Things to consider before moving into a summer crop:
Herbicide restrictions:
One of the most important considerations for determining if and what potential crop could be planted following a non-harvested wheat crop is the chemistries used during the year. Table 1 gives rotational restrictions on some commonly used winter wheat herbicides. While this provides a summary or shortened list of herbicides and their rotational restrictions, producers should check individual labels if other herbicides were used. It should also be mentioned that minor plant injury could occur past the stated months following application given differences in soil conditions such as pH, soil moisture, and soil temperature.
Wheat herbicides rotation restrictions
Heavy wheat residue:
One thing that needs to be decided is how the grower will manage the heavy wheat residue associated with the failed crop. Certain situations exist that may result in limited to no residue (i.e. haying or heavy disease pressure); however, most producers will be faced with high residue load which may potentially be heavily matted and may pose challenges for producers to plant through. In these situations, producers may need to resort to tillage. The amount and intensity of tillage will greatly depend on the amount of residue left in field. In high residue situations, producers may need to run one or several primary tillage practices followed by a secondary or finishing tillage event. However, in lower residue conditions or if the producer has access to no-till equipment, no tillage may be needed to achieve a successful stand.
Overall cropping system:
When deciding to terminate an existing wheat crop and/or to plant a successive crop, decisions need to be evaluated at a systems level. Growers need to ask themselves whether this makes sense within their system and if it fits into their long-term system goals. If the original intent for the system was to double-crop following wheat harvest, it needs to be determined if the remaining economic benefit without the yield from the wheat crop. This may be at least partially alleviated if any profit can be made from the wheat crop (i.e. hayed) but needs to be evaluated on a specific field basis. The next question will be what the successive crop would have originally been? If a summer crop is planted, some systems will need a winter fallow as to not overstress the system, harvest the summer crop prematurely, or plant the successive winter crop past the appropriate timeframe. In this case it needs to be determined if that is suitable for the long-term system goals. Many of these scenarios exist and each could be beneficial or not within individual systems; however, growers need to evaluate these individually and determine what works best for their current situation and their long-term production goals.
Overall, the decision to move to a replacement crop can be very challenging. It cannot be stressed enough that in most situations maintaining the existing crop is likely the best option for most producers.
Josh Lofton
Assistant Professor
Cropping Systems Extension Specialist
376 Agricultural Hall
405-744-3389
josh.lofton@okstate.edu
Herbicide and UAN tank mixed for top-dress
Spring is the time that many wheat producers apply herbicide and nitrogen (N) fertilizer. For many this can be accomplished in a single pass by tank mixing the herbicide and UAN. In most cases this is an effective practice which eliminates one pass over the field. There are some scenarios in which this practice is ill advised. One such scenario is high temperatures which would lead to excessive leaf burn and crop damage. The other scenario is no-till and that will be the focus of this article. Ruling out warm temperature tank mixing herbicides and nitrogen, assuming the herbicide can be tank mixed, is a good practice. No-till on the other hand can be a different issue.
Situations with a lot of residue and smaller wheat is common during top-dress.
The problem in no-till comes from the liquid application method needed to apply herbicides, flat flan. To get a good kill with the herbicide the spray pattern needs to have good coverage, i.e a lot of small droplets to ensure maximum surface area impacted. Unfortunately there are four primary fates of UAN when applied via flat fan nozzles. The UAN could be taken directly up into the wheat plant via absorption through the leaves, the UAN could reach the soil and go into the soil solution or absorbed onto the soil itself, the UAN can be taken up by weeds, or the UAN droplet may hit dead plant tissue and be adsorbed into the residue.
UAN applied with a flat fan will hit a growing plant, the soil, or residue.
The fourth fate of UAN presented is what can make the tank mix less efficient than a two pass system. In a no-till system any UAN that hits residue should be counted as lost, for the short term. The decision to go with a one pass or two pass system can be aided by evaluating the amount of canopy coverage. For example if the no-till field has 50% canopy coverage then one could estimate 50% of the UAN applied via a one pass system would be tied up in the residue. The cost of a second application could then be compared to the lost N. If 15 gallon of 28-0-0 was being applied then approximately 22.5 lbs of N would be tied up by the straw. At a price of $0.40 per lb on N, that is $9.00 worth of N. Conversely if the canopy coverage was 80% only 20% or 9 lbs of N would be tied up in the residue. Saving the $3.60 in nitrogen would not justify a second trip over the field. Luckily OSU recently released the Canopeo app which uses a cell phones camera to take pictures and quickly and accurately determine % canopy coverage. Canopeo is available for iOS and android http://canopeoapp.com/.
In fields with a high amount of residue or limited canopy coverage UAN should be applied with streamer nozzles. This will concentration the fertilizer into streams which will allow the UAN to have enough volume to move off the residue and into the soil.
So as the decision is being made to tank mix herbicide and UAN or make two passes take into consideration: % canopy coverage, rate of UAN (how much could be lost), cost of UAN per pound, and cost of a second trip over the field.
Below is an excerpt from the publication Best Management Practices for Nitrogen Fertilizer in Missouri; Peter C. Scharf and John A. Lory. http://plantsci.missouri.edu/nutrientmanagement/nitrogen/practices.htm
Broadcasting UAN solution (28 percent to 32 percent N) is not recommended when residue levels are high because of the potential for the N in the droplets to become tied up on the residue. Dribbling the solution in a surface band will reduce tie-up on residue, and knife or coulter injection will eliminate it. Limited research suggests that the same conclusions probably apply for grass hay or pasture. Broadcast UAN solution is also susceptible to volatile loss of N to the air in the same way as urea, but only half as much will be lost (half of the N in UAN solution is in the urea form).
Some thoughts on pre-plant nitrogen and a little outside the box thinking
It is that time of year, every Co-op I drove by the other day had a line of trucks pulling anhydrous tanks and the spinner spreaders were being loaded. For those of you who haven’t applied your nitrogen yet lets discuss the options traditional and nontraditional.
Anhydrous Ammonia, 82-0-0: by far the most widely used N source is the southern Great Plains. While it is not the most enjoyable to work with it is the cheapest per pound of N and that leads to its wide spread use without Oklahoma wheat production. Just a few simple rules with NH3, get it in the ground and close the row behind you. In conventional till this is usually easier unless the ground is too wet or too dry. In no-till this may be a little more challenging but usually easily accomplished. With the rise in low disturbance applicators I am seeing more and more acres of no-till receiving NH3. Last year I was in a field of stripper stubble and I had a hard time finding where the rig had run, minus wheel tracks.
Urea, 46-0-0: is second on the hit list in nitrogen sales in our state. It is a safe source that is easily handled and applied. In a conventional till system where the urea can be worked in shortly after application it is a very efficient and effective source. Unfortunately when it is applied to the soil surface and rain is the method of incorporation we can experience between 5-60% N losses. The losses come from how urea is converted to plant available ammonium (NH4). For urea (NH2)2CO2, to be converted to plant available NH4 it needs the enzyme urease. Urease is present everywhere but in the highest concentrations on plant residue. The figure below shows the reaction, urease converts urea into NH3 as soon as the prill dissolves. In the presence of moisture the NH3 (gas) is turned immediately to NH4 (solid) and is absorbed onto the soil particle.
Graphic of Urea’s conversion to plant available ammonium.
The problems come when there is no soil particle for the NH4 to bind with. It usually takes 0.50 inches of rain or irrigation to fully dissolve and incorporate urea into the soil. So if we only get a few tenths or hundredths, even heavy dews, some of the urea will dissolve, be converted to NH3 then NH4 and be left on the plant/residue. When the moisture dries, some or all of the NH4 goes back to NH3 and will gas off into the atmosphere. I have even seen this happen when urea is applied on a wet/damp soil, not incorporated and it doesn’t rain for significant period of time. If the temps are cooler the urease is slower so less of the urea is converted to NH4, but if the temps are warm 60+ degrees these little enzymes can act very quickly.
Urea placed on the surface of a wet soil under two temperature regimes. White text is the number of hours after application.
Urea placed on dry soil, Top row: dry soil no water added, Bottom left, moisture added from subsurface, Bottom right : simulated rain fall event of 1/2″. White text is the number of hours after application.
Below is a short video on using urea fertilizer.
While the recent rains are a blessing and will surely help germination, it is not aiding our N use efficiency especially in no-till. That is why in some parts of the state you may see some grain drills running right now. Some of those producers are not planting wheat they are actually applying there pre-plant urea. I have even been told in the SW part of the start some producers are using air-seeders to apply their urea. While this seems like a costly venture I have worked with the Ag Economist to create a calculator to figure up the break even for when it would pay to use an air-seeder over the traditional spinner spreader in no-till. We hope to put the finishing touches on it in the next few days. When it is completed it will be shared on this blog.
Liquid Urea Ammonium Nitrate, 32-0-0 or 28-0-0: while this is one of the more expensive forms of N many producers are utilizing this source because the can pre buy and store on site and as sprayer get larger they can cover a significant amount of ground quickly. For the most part UAN is used in no-till and is a great source. I always recommend that applicators use streamer nozzle or streamer bars to apply UAN. When UAN is applied via a flat fan nozzle it spreads the fertilizer across the residue allowing a significant portion to be tied up. The streamers concentrate the fertilizer into streams/bands reducing contact with residue and increasing the amount of UAN that reaches the soil surface.
Timing and Rates
The cost of anhydrous, about $0.1 to 0.12 less per pound N less than urea is driving its use this year. The lower price is also driving a significant about of producers to go with 100% of their N pre-plant. While this makes for sound economics now having all of your N upfront is like putting all of your eggs in one basket. If we do get that cold and wet winter as some are calling for this presents a great chance for the N to move down the soil profile and down the slope. I have always recommended split application. This allows a producer to judge the crop throughout fall, winter and even yearly spring and adjust his or her N plan accordingly. For those who plan to graze there is still a need to get enough N down to produce fall forage, this may be 50 to 80 lbs of N, but for grain only production planted later in the fall a typical crop may only need 20-30 lbs of N before going into winter. The old rules of thumb, 2 lbs N per bushel and 30 lbs N per 100 lbs of gain still work and are better than a guestimate but we have better ways. Right now is the time to plan to apply N-rich strip, a strip in the field with 40 to 50 lbs more than the rest of the field. These strips can be applied with a variety of applicators, but as long as the N goes down in at least an area 10 ft wide by 300 ft long it is good to go.
Just a few of the applicators used for putting out N-Rich Strips. ATV Sprayer, Receiver Hitch mounted Sprayer, Road sprayer with a rear boom, pull type spinner, large sprayer, push spreader. Not shown is NH3 applicator.
Below is a N-Rich Strip 101 video.
If you have got the N-Rich strips out you can set back and watch to see when and if they develop. If you can see the strip you know you need too fertilize.
While many are not ready to think about top-dressing yet, it is never too early. Don’t be afraid to think outside the box. Oklahoma’s springs tend to present the perfect conditions for N loss when urea is the primary N source. This year in a 4R Top-dress Nitrogen Application Demo, at Lahoma and Chickasha, we are going to apply just about every available commercial source in about every possible manor. Urea will be broadcast, coated with inhibitors, applied with a grain drill, NH3 will be knifed in, and UAN will be applied with flat fan nozzles, streamer nozzles and knifed in. As technologies improve and the cost of N remains relatively high the options for top-dress N application will continue to improve. The economics of wheat production don’t look great right now so don’t be afraid to think outside the box, even if it does raise the eyebrows of your neighbors. Fill free to contact myself or your local extension educator if you have any questions about N application.
John Deere double disk drill used to apply urea in-season.
WAKO NH3 applicator used for in-season application.
Down and Dirty with NPK 