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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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On Farm Nitrogen Rate Study Results 18-19.

Vaughn Reed, PhD. Student Precision Nutrient Management|
Brian Arnall Precision Nutrient Management Extension Specialist.

A focal point of the Precision Nutrient Management team is the evaluation of fertilizer timing.  Mr. Souza’s research shared in the blog post How Long Can You Wait has shown, with three years of data, that if fertilizer application is delayed until in-season, not only will optimum yield reached but the protein content will be increased.  The study below which has just had one year of data will provide additional insight.

While the Sousa work focused on a single rate of nitrogen applied over 12 different application dates at on a few OSU research farms this study evaluated a range of N rates applied both pre-plant and in-season on farmer fields across the state. The rationale for a wide distribution was to achieve the primary goal of the study, which was to add regional specificity to the current sensor based nitrogen rate calculator (SBNRC www.nue.okstate.edu). More on that as the research matures. In order to achieve the range needed to reach the goal small plots were set up in numerous locations throughout the central/western portion of the state and hand harvested at maturity.  In Figure 1 below, you can see the sites for the 2018-2019 growing season, as well as the prospective climate zones.

Figure 1. Location of the 2018-19 on farm winter wheat nitrogen response studies. Color shades represent climatic zones.

The trials were set up with four rates (25%, 50%, 75%, 100% of yield potential rate), two timings (pre-plant and in-season application), and a zero N check.  Applications were applied using ammonia nitrate as the source, in order to minimize losses due to volatilization. Eight trials were harvested in six counties, and three different climatological zones.

The data from the first year of this trial confirmed the results seen in the Sousa study. In-season application of nitrogen was more efficient in terms of yield and quality than equivalent rates applied pre-plant. Out of the eight locations harvest, only two had a significant grain yield respond to the addition of N fertilizer.  However, all eight locations the addition of N had significant positive impact on protein content. When looking at pre-plant versus in-season application, grain yield was not statistically significantly different from each other at any location.  Protein content of in-season N was however significantly better than pre-plant application at 5 of the 8 locations.

Figure 2.  below is the results from the Byron and Perkins location.  At both sites all fertilizer application for this location responded above the check plot (0 N).  At Byron we can see an increase in yield up till about 60 bu/ac in both the preplant and topdress application.  The proteins increased with the rate of fertilizer applied.  In both of the responsive locations while in-season N was never statistically greater than pre-plant N in all cases the in-season application had numerically higher yields and protein.

Figure 2. Winter wheat grain yield and protein content results from on farm nitrogen rate studies performed in 2018-19 at Byron Ok, and Perkins Ok.

The next table below is from the Capron location.  This location did not yield a significant increase in yield from the application of N across the board, including timings.  But even though there was no impact on yield protein increased. In both of these locations the increase due to in-season N was statisically greater then the pre-plant. This response is replicated in three other locations in this trial that did not have yield respond.

Figure 3, Winter wheat grain yield and protein content results from on farm nitrogen rate studies performed in 2018-19 at Capron Ok, and Lahoma Ok.

This is one years data, across eight locations. The trials will be continued this fall (2019) for another growing season, and Mr. Souza is repeating his trial as well.  Everything that has done thus far has shown that not only is grain yield not lost by not fertilizing at pre-plant but by delaying all fertilizer applications till in-season , grain yield is maintained if not increases and protein levels are consistently higher.

Figure 4. Crew hand harvesting on farm N rate plots. Hand harvest is preferred because A) we are able to harvest at a higher moisture content ahead of the farmers combines B) we do not have to haul the plot combine across the state.

 

For question, comments, or request for on farm studies please contact.

Brian Arnall
B.arnall@okstate.edu
405-744-1722

Nitrogen rate and timing for a forage wheat crop. Year 1 Results.

Written by
Mr. Bronc Finch, PhD. Student, Precision Nutrient Management. 
Dr. Brian Arnall, Precision Nutrient Management Extension Specialist. 
In cooperation with Dr. James Rogers, Noble Research Institute. 

With the amount of wheat acreage in Oklahoma being utilized for grazing cattle, and much of that land grazed completely instead of harvested for grain, many questions have arose regarding the management of grazed cropland. A major question in the management of a graze-out wheat crop pertains to fertilizer management strategies. A study developed in co-operation with the Noble Research Institute is attempting to answer these questions among others. In 2019 the trial was established at three locations: near Lake Carl Blackwell in Stillwater, OSU South Central Research Station in Chickasha, and Noble Research Dupy farm in Gene Aurty, Oklahoma. Each of these three sites were setup with three nitrogen (N) treatments in Gallagher winter wheat, with 2 pre-plant applications of 60 and 120 pounds per acre, and a 60 pound pre-plant and 60 pound top-dress application. Grazing simulation harvests were taken at two times with the top-dress N being applied after regrowth was noticed following the winter season. The Dupy location was planted late and therefore only had a single harvest at the end of the season. Rising plate meter measurement were collected at feekes 7.5 and represented in the graphs below as Mid-season. The Chickasha location revealed unexpectedly high residual soil N levels, which resulted in no differences in dry matter biomass for the first harvest, which was delayed until early march due to excessive rains. The second harvest at Chickasha did show treatment differences with a 0.4 ton difference between the 60 and 120 lbs preplant N rates and increase of 0.8 ton increase over the 120 lb pre-plant when the additional 60 lbs of N was delayed. LCB had a timely first harvest in December resulting in the 120 lb N application outperforming the 60lb N applications by ≥0.33 tons. The second harvest further showed how the split application of N proves beneficial for biomass production. As the split application increased yields by 1.7 and 2.6 tons over the 120 lb and 60 lb preplant applications, respectively. The Dupy location revealed no significant difference in dry matter biomass yield between N treatments at the time of the rising plate meter measurements or for the final cutting.

Figure 1. Dry matter harvest results for each of the harvest dates from the graze out wheat trials from the Chickasha, Lake Carl Blackwell, and Dupy locations for three fertilizer treatments. 60: 60 lbs of nitrogen applied preplant, 120: 120 lbs of nitrogen applied preplant, 60/60: Split application 60 lbs of nitrogen preplant and 60 lbs applied top-dress. Dupy only had one harvest date, the Mid-season yield is estimated via rise-plate measurements taken at Feekes 7.5.

 

The Chickasha and Lake Carl Blackwell (LCB) locations produced an increase in total yield with both the increase of applied N and the split application of N. The 60 lb increase in applied N at preplant, 60 lbs vs 120 lbs, produced a 0.7 and 1.2 ton increase in total dry matter harvested at Chickasha and LCB, respectively. As expected an increase in N increased the yield of wheat biomass for grazing production. The top-dress application, which was made as a late season post Feekes 6 (hollow stem), produced more biomass for graze-out wheat production. The split application of 60 lbs of N preplant and 60 lbs of N top-dress increased dry matter by .8 and 1.3 tons over 120 lbs applied preplant at Chickasha and LCB, respectively. Chickasha yielded higher biomass production than the LCB location due to increased residual N.

Figure 2. Total dry matter harvest results for the graze out wheat trials from the Chickasha, Lake Carl Blackwell (LCB), and Dupy locations for three fertilizer treatments. 60: 60 lbs of nitrogen applied preplant, 120: 120 lbs of nitrogen applied preplant, 60/60: Split application 60 lbs of nitrogen preplant and 60 lbs applied top-dress.

For the following discussion remember that protein is determined by N concentration, so that a increase in N uptake is the same as an increase in protein. Evaluation of the N uptake (% N in the biomass x amount of biomass harvested) over the season revealed treatment effects at all locations, which was not seen from biomass yield. Chickasha and LCB revealed a 20% or greater increase in N uptake with the 120 lb application over the 60 lb application of N at pre-plant. The late season top-dress application yielded a 3, 27, and 27 percent increase in uptake for Chickasha, LCB, and Dupy locations, respectively, over the 120 lb pre-plant application. Although, these results are expected from these results, there are a few things we did not expect. The 120 lb N application did not increase the N uptake above that of the 60 lb application. However, the split application of N resulted in an additional >40 lbs uptake, aka increased protein.

Figure 3. Total nitrogen uptake results for the graze out wheat trials from the Chickasha, Lake Carl Blackwell, and Dupy locations for three fertilizer treatments. 60: 60 lbs of nitrogen applied preplant, 120: 120 lbs of nitrogen applied preplant, 60/60: Split application 60 lbs of nitrogen preplant and 60 lbs applied top-dress.

This study also includes summer forages with and without additional fertilizer. The study will be continued for multiple years on the same locations to evaluate the impact of management on production and soil characteristics.  But one surprising note has already been made, in all three locations a greatly delay top-dress still increased N-uptake. In two location it significantly increase yield and protein. This data is falling in line with the grain only data (How late can you wait) showing that an application of N at Feekes 6 (Hollow stem) and even shortly after can provide positive return on investments.

 

For any questions for comments please contact
Brian Arnall
b.arnall@okstate.edu
405-744-1722

 

Watch Forage Nitrate Closely on Certain Crops

Nitrate is one of the major nitrogen (N) forms utilized by plants. Excessive nitrate accumulation can occur when the uptake of nitrate exceeds its utilization in plants for protein synthesis due to factors such as over N fertilization and stressful weather conditions. It can be toxic to livestock when too much nitrate is accumulated in the forage crops. Sorghum and millet have been noted as having a high potential for accumulating nitrate. Producers should watch their forage nitrate closely to avoid cattle fatality and to better manage their hay crop since we have seen many high nitrate forage samples every year. Normally, drought stress, cloudy weather and other climatic conditions will enhance nitrate accumulation in the plant. In addition, forage planted in failed wheat fields with high soil residual nitrogen unused by wheat can result in high forage nitrate problem too.

Figure 1. Summary of our laboratory nitrate test results in the past on two major warm season forage crops.

It is considered potentially toxic for all cattle when nitrate in the forage is greater than 10,000 ppm. Producers should avoid grazing or feeding with high nitrate hays. More detailed interpretation can be found from OSU Extension Fact PSS-2903 Nitrate Toxicity in Livestock. The most reliable way to find out nitrate in the hay is to collect a representative sample and have it tested by a laboratory. OSU Extension Fact PSS-2589 Collecting Forage Samples for Analysis highlights the proper techniques to collect forage samples. Samples can be submitted for nitrate and other forage quality analyses to the Soil, Water and Forage Analytical Laboratory in Stillwater through the local county extension office. We normally have the results ready within 24 hours form the time when sample is received by the lab. However, many samples we receive at the lab were not sampled properly. More attention should be paid on sampling standing forage, such as a haygrazer by following the right procedures:

Clip at least 20 representative plants at grazing or harvesting height from the suspected area. Cut the whole plants (include leaves and heads) into 2-3” long pieces, combine and mix well in a bucket.

Fill the cut sample into a forage bag. Use quartering to reduce the amount if there is too much sample to send to a lab.

Put the forage bag into a plastic bag will give you more accurate moisture content, but never put plastic bags inside our forage bags.

There is also a quick screening test using diphenylamine at your county extension office. This video shows how to properly use the test kit: https://www.youtube.com/watch?v=vArUP6KFQFI&feature=youtu.be

 

Hailin Zhang

Department of Plant and Soil Sciences

Hailin.zhang@okstate.edu

DAP in short supply? Revisiting, DAP vs MAP, Source may matter!

From mid August through October, fertilizer applicators and grain drills are running across the southern great plains wheat ground. Di-ammonium Phosphate (DAP 18-46-0) is maybe the most popular form of phosphorous (P) utilized in wheat production today. DAP delivers a high content of nitrogen (N) while efficiently binding the toxic aluminum (Al) ions low pH soils. However due to the flooding that occurred throughout the spring the Ports have been closed and DAP could be in short supply. I have heard that many companies and Co-ops have already sourced Mono-ammonium phosphate (MAP 11-52-0) to supplement the lack of DAP for our early planted wheat crop. With this happening, I wanted to share some points about the two sources. In a broadcast incorporated scenario I do not have much preference for one over the other. It is when producers are applying the fertilizer in-furrow or applying to alleviate Al toxicity that source can matter. As described in the post below, in a soil with a neutral pH DAP and MAP perform equally well. So in this scenario I give MAP a slight edge over DAP if the price is the same. I say this as you can run less material per acre with MAP and refill a little less often. Many worry about the drop in N delivered with MAP versus DAP but in my work I see that is the P in the starter that gives us a good response and not the N, which can be delivered with pre-plant or top-dress. However, DAP wins out in soils with a pH below 5.5. The original blog below shows the results when DAP and MAP are banded in acidic soils using the same rate of P per acre.  The reason we see this happen is that when MAP dissolves it forms a slightly acidic solution (approx 4.0) while DAP will dissolve to form a slightly basic solution (approx 7.5). In our work BOTH DAP and MAP increased yield above the check in acidic soils, which goes to show MAP is an affect tool for short term remediation of aluminium toxicity (Band P for Al toxicity Blog). However it might require more MAP per acre to reach the equivalent results. Because of what we saw when comparing the two sources at equivalent rates of P, I would recommend increasing the rate of P2O5 from 30 lbs per acre to 35 or 40. This would be going from 65 lbs of DAP to 67-77 lbs of MAP per acre.

So the take home would be as this wheat season takes off and you find that DAP is hard to locate and you A) Have overall neutral (5.5+) pH levels do not hesitate using MAP. Run the normal amount of material getting a few extra lbs of P or apply less material to get the same amount of phosphate. B) Have a acidic situation and are banding to alleviate aluminum toxicity use the same amount of material or a little bit more.  Keep in mind in acidic soils with a low soil test P level you have to apply enough phosphate to take care of the Al and enough to take care of the P deficiency. Note the results of the NPKS wheat response strip (NPKS BLOG)

Original Post Published July 18, 2016
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.

Picture1

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 yield, 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.

MAPvDAP2

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.

State pH

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.

How long can wheat wait for Nitrogen? One more year of data.

Update to the delayed nitrogen study.

Joao Bigatao Souza, PhD. Student Precision Nutrient Management|
Brian Arnall Precision Nutrient Management Extension Specialist.

Due to the surprising results seen from the delayed N study that was first reported below we repeated the the study for a third year at two locations, the Lake Carl Blackwell Research farm near Perry OK and the Ballagh Research Farm near Newkirk OK. Due to the excessive rain fall the wheat was planted and trials established later than normal and a cool winter and spring and winter the crop green up (end of dormancy) was delayed compared with the two first cropping seasons. For this season we started applications before visual symptom difference between the N-rich Strip (pre-plant) and the rest of the field actually occurred. This can be seen with the pre-plant dates of late Oct-Early Nov and the notation of visual difference above the yield bars. Just as the other two previously crop years, the timing of the application did impact wheat yield and protein. In this season at LCB we see a increase in yield with application of N during the first part of March compared to the preplant with yields dropping off below the preplant when N was applied in mid April. At the Ballagh farm there is no yield benefit from delaying N after preplant but there was steady increase in protein, again at this location yield is lost when N was delayed past mid April. In both of these locations mid April was after the growth stage of Feekes 7. After three cropping seasons with some extremely different weather patterns we saw that in this work, pre-plant N was never better than in-season N applied prior to mid April, Feekes 7. In most cases N applied in-season yields and protein values were greater than that of the pre-plant treatment. My take home message from this project is multi fold; First, pre-plant may be cheaper and easier but it often falls short of in-season applications, Second that there should be no reason to rush putting top-dress nitrogen on. The application window is much wider than most ever expected and the closer we get to peak demand the better the yield and quality will likely be. And third, and final make the application of nitrogen when the conditions are the most conducive to getting the N in the ground and limiting losses.

Note: This trial used ammonium nitrate as its N source to evaluate the plants response and remove potential fertilizer efficiency problems. However while these trials were being conducted mirror studies using Urea as the N source were also being conducted. Those results are currently being compiled right now and we hope to share the results soon.

Grain yield and protein results from the delayed nitrogen study preformed at the Lake Carl Blackwell near Perry in 2018-2019. 11/7/2018 was the pre-plant application date.

 

Grain yield and protein results from the delayed nitrogen study preformed at the Ballagh research farm near Newkirk in 2018-2019. 10/24/2018 was the pre-plant application date.

Questions for comments feel free to contact me via email at b.arnall@okstate.edu

Original Post made Oct 1, 2018

How long can wheat wait for Nitrogen?

Joao Bigatao Souza, PhD. Student Precision Nutrient Management|
Brian Arnall Precision Nutrient Management Extension Specialist.

The N-rich strip method allows wheat producers a greater window of decision making regarding the application of nitrogen (N) fertilizers. Besides having greater accuracy in N rates than standard methods (based on the SBNRC – OSU) also helps to reduce costs in the production system and to preserve the environment avoiding over N applications.

With the experiments performed in the last two crop seasons (2016/18 and 2017/18), we can now be even more accurate with regard to the best application time to increase the N use efficiency by the crop. 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 preplant N was applied other than trt 1, and all locations had residual N under 15 lbs 0-6” sample.

The first visual response to fertilizer N ranged from November 11 to February 5 (Table 1). The soil can have residual N from the previous season which can supply the subsequent crop in the beginning of the development what makes the wheat not demonstrate any sign of stress in the early season. For example LCB2017 a and b which were located 100 yards apart but under a different point in the crop rotation (LCBa was wheat after wheat and LCBb wheat after canola) had a 30 day difference in date of first N response. This range in first and last dates allowed us to evaluate N application over a wide range of dates and determine whether the first sign of stress is actually the best indicator of top dress application timing.

Table 1 shows the planting date, date of first visual difference (0DAVD) and each of the application dates for all locations. Different colors represent individual months. Hollow stem occurred approximately Feb 20 in the 2017 crop and March 10th in the 18 crop.

 

Image of the 2016-17 Perkins location. Image collected March 21 2017.

As shown in the Tables 2 and 3 below only three of the 78 comparisons made back to the pre-plant application were significantly less in terms of grain yield. All three of these comparisons where from when N application was delayed until late March or April. When the delayed applications were compared to 0DAVD yields only two of the 68 comparisons showed a significant decrease on yield. One was the pre-plant application for LCB2017a while the other were the 63DAVD application for LCB2017b. In most locations applications made in March yields were at the highest point, however when delayed till April yield trends on the downward trend. The 2017 crop reached hollow stem (Feekes 6) around Feb 20th while the 2018 crop reached hollow stem around March 10th.

Grain protein concentration was decreased only once when compared to both the pre-plant and 0DAVD treatments. This one timing, LCB2018b 64DAVD, was the only application made in May. During this time the crop was in the early stages of grain-fill. In all locations delaying N application until February/March increased grain protein content above the check, and in most cases above the 0DAVD trt.

Tables 2-3 shows the winter wheat grain yield and protein concentration, respectively, of all treatments. The colors of the cells represent statistical difference from the Pre-plant treatment. Treatments with cells shaded yellow are equal to the pre-plant, Green is statistically greater than while red is statistically less than the pre-plant treatment.

 

2016-2017 Delayed nitrogen winter wheat grain yield and protein results. For the locations of Perkins and N40 the Dec-1 application has a higher yield due to a 2x application of N to equal 180 lbs.

 

2017-2018 Delayed nitrogen winter wheat grain yield and protein results. The Perkins location in 18 was the only location in the study which did not have a statistically significant response to added N.

All the data was combined and plotted by cumulative GDD’s>0 from planting (GDDFP) across all locations to determine a general “best” timing. Using the pre-plant application yield as a base there was no yield loss if the applications was made prior to the 143 GDDFP. When the results were normalized by 0DAVD N there was no yield loss if the applications were made prior to 130 GDDFP. The quadratic model created provides the opportunity to identify the point of highest grain yield, which was approximately 94 GDDFP. In terms of the relationship between the application of N based on GDDFP and % of protein content on the grain, a linear response of N delay application observed for grain protein concentration. Our results suggest that the later the application, the higher the protein % in the grains.

Growing degree days > 0 from planting and equivalent calendar days for all experimental sites (Lake Carl Blackwell, Perkins, Lahoma, Stillwater) utilized in the study evaluating the impact nitrogen fertilizer timing on winter wheat, conducted in north central Oklahoma over the 2016-2017 and 2017-2018 winter wheat growing seasons.

We have concurrent work looking at similar approaches with other sources of N such as Urea and UAN. While all of  these studies are being continued the past two years of work have presented some easy take homes.

First: Timing of N application does matter, but yellow wheat does not necessarily mean yield loss.
Second: Two years in a row ALL Nitrogen could be delayed until hollow stem without yield Loss, in fact yields of trts with N applied at this time typically better than that of the pre-plant.
Third: Protein content increased as N applications was delayed.
Fourth: The conclusions of this and other studies support that N-Rich Strip concept does not increase risk of lost yield.
Fifth: Applying the majority of the N at or just after hollow stem maximized grain yield and protein with a single shot.
Sixth and Final: Be more concerned about applying N in an environment conducive to increased utilization and less about applying at the first sign of N stress. Take a look at the wheat N uptake curve by K-State.The crop really doesnt get going in terms of N-uptake until jointing i.e. hollow Stem.

Wheat N-uptake. Figure adapted from Lollato et al.

Questions for comments feel free to contact me via email at b.arnall@okstate.edu

Double Crop Response to Additional N, P, K and S.

Vaughn Reed, PhD. Student Precision Nutrient Management
Brain Arnall Precision Nutrient Management Extension Specialist.

Data presented below are the results of Mr. Reeds Masters research project.

On farm research trials are important, because they give us the ability to see responses over a larger geographic area, and even more importantly, evaluate our recommendations on fields that are managed by producers, not researchers.  They also allow us to look at current production practices and see if there are any missed opportunities. Several years ago, we looked at whether producers were leaving yield on the table by not applying enough nitrogen (N), phosphorus (P), potassium(K), and sulfur (S) to winter wheat. We did this by applying strips of N, P, K, and S fertilizer on farmers’ fields with the instructions to not change their fertilizer management strategies. If one or more of the strips resulted in higher yields then it could be assumed that either the nutrient was under-applied by the producer, or in the case of N, lost.  That study concluded that at 75% of the locations, yield was maximized by the producer with [their respective] NPKS management system, however the greatest responses came from the addition of P and that Oklahoma State University’s soil testing and analysis was adequate for nutrient recommendations. That studies results were published in 2017 and is open access, so available for anyone to read. https://dl.sciencesocieties.org/publications/cftm/abstracts/3/1/cftm2017.02.0014

Locations of double crop fertility response strips applied in the summers of 2016 and 2017.

There are many producers around the state that follow winter wheat with double crops (DC). Often, this practice is done with limited inputs to reduce economic risk.  Oklahoma State does not make different recommendations for DC or full season crops, with the exception that yield potentials can differ.  In 2016 and 2017 we duplicated the Wheat NPKS study across 3 double crops (soybean, grain sorghum, sunflower) following winter wheat and canola. With a recent climb in DC yields we wanted to investigate if producers were applying enough nutrients to maximize grain yield. Additionally it would allow us evaluate the accuracy of OSU’s soil test based fertilizer recommendations in a double crop. Over the two years, 61 on-farm sites ranging from central to NE Oklahoma had 200 lb/ac of product per nutrient applied in strips 6ft wide by 150 ft long.  Urea (46-0-0), triple super phosphate (0-46-0), muriate of potash (0-0-60), and gypsum (0-0-0-19) were used for sources N, P, K, and S, respectively (92 lbs N, 92 lbs P, 120 lbs K, 38 lbs S). In most cases the fertilizer was applied post planting and post-emergence to ensure strips were applied an areas with good stand.

NPKS Strip Applicator. This ground driven 3pt rig uses Gandy boxes to deliver fertilizer into tubes which is then blown, by a PTO driven fan, out into strips 6 feet wide, per box. This applicator was putting out 200 lbs of Urea, 0-46-0, potash, and gypsum out per acre.

Much like with the wheat-NPKS study 75% of the locations did not respond to additional fertilizer. Twenty treatment comparisons of the 244 made across all 61 locations (50 soybean, 7 grain sorghum, 4 sunflower) yielded a statistically significant change in yield due to the addition of N-P-K-or S. For this report, a comparison was the yield of each nutrient versus the non-treated check, therefore there were four comparisons made per location. Seventeen of the twenty positive responses were found in soybean, three with grain sorghum, and no responses were found in sunflower plots.  Lack of response from grain sorghum and sunflower locations is contributed to small amount of grain sorghum and sunflower fields in the study.

Double crop soybeans in Ottawa County with strips of nitrogen, phosphorus, potassium, and sulfur applied post plant.

Nitrogen rates, for non-legumous crops, are yield driven, meaning the higher yielding a crop, the higher amount of N required.  Both grain sorghum and sunflower crops, due to neither being legumes, were expected to see N response, especially to those locations that applied little to no N to begin with.  A yield response from the addition of N was found in one grain sorghum location, where the producer application was not enough to maximize yield, and the additional N pushed the yields.  As expected, there were no soybean locations that responded to the addition of N.

Phosphorus and potassium are both sufficiency based, not yield driven.  This means that if the soil is at 100% sufficiency, the crop will produce at its highest rate achievable, based on that nutrient.  100% sufficiency for P and K are approximately 65 STP and 250 STK, respectively.  Phosphorus and potassium strips yielded the most results, especially in soybean locations. Of 20 responses, five responses were due to P, ten due to K, and four due to S. Locations that responded to the addition to P were locations that either had low levels of STP (approx. 80% sufficiency or less), or had low pH, which leads to less availability of P (pH>5.0).

Potassium yielded the most positive results, with ten responsive locations, as well as the most interesting results, with only three sites falling below 100% sufficiency.  The other responses were attributed to having low Cl levels (Cl, as in Chloride, which while responses are rare, is a necessary nutrient, and sometimes can lead to losses in yield, especially in sandy environments), as well as drought stress conditions.  Potassium has been shown to have a vital role in nutrient uptake and water retention, as it is found to be critical for root growth, and these are displayed highest in crops found in drought like conditions. One hypothesis for the K response is related to root growth. The later planted DC will spend less resources in root development before going reproductive. Soybean is a heavy user of K, combine smaller roots, typically hot drier soils, and high K demand it is not surprising to find this occurrence.

Sulfur, while not wide-spread reported in Oklahoma, has recommendations by OSU built on a yield driven scale.  There were four responsive locations found in this project. While one location had low soil test S values there were located areas that received high rainfall events during the growing season, and therefore the response was attributed to leaching of S.

So, after all that, what is the bottom line?  Here is our observations:

  • Producers maximized yield 75% of the time, with 25% of locations responding to any additional nutrient.
  • The 20 responses to additional nutrients occurred across 15 locations, four locations had responses to more than one nutrient
  • By nutrient: Note for P and K, due to site variability it was not expected to observe statistic yield increase due to P or K unless soil test was below 70% sufficiency, of which no location had soil test P or K below 70%.
    • 38 locations were below 100% sufficiency of phosphorus, with five observed responses
    • Seven locations were below 100% sufficiency of potassium, two observed responses. An additional eight locations responded that were not predicted by soil test
    • Based on pre-plant soil test there were no sites expected to respond to the addition of Sulfur, 4 locations did respond.
  • Soil test results were adequate in correctly identifying locations that would not respond to the addition of nutrients (93.5% accurate), while not as accurate at predicting sites that would respond.
  • For K, soil testing was less accurate, as eight of the ten responsive locations had soil test values above 250 soil test K (125 ppm or 100% sufficiency). For this reason, we are currently doing work evaluating K recommendations for soybeans.

This work confirms that of the fields we evaluated, the majority was not yield limited by N, P, K or S. However, as with anything, we have more work to do in order to further refine our recommendations, and always looking to learn more about how to aid producers.

Recent Weather Causing Corn (and Sorghum) Injury From Pre-emerge Herbicides

With the brief window of dry ground last week my crew went at full speed planting and applying pre-emergence. Today I am sitting at home with campus closed due to the potential to severe weather with a forecast of 4-6 inches of rain for the areas I planted. Combine the recent planting activities and limited windows for pre-emergence applications, I will not be surprised if we don’t start seeing injury in some of the sorghum that was just planted before the rains. I would also add the over the years I often see bleaching in sorghum, that looks similar to zinc and/or iron deficiency, caused by atrazine injury.  This typically occurs when atrazine is applied prior to a heavy rain. The atrazine is washed down slope and into the rows, the injury is almost always seen in low lying areas.  The crop usually grows out of it.

Atrazine injury in sorghum. Heavy rains followed application. Pic via Rick Kochenower.

Atrazine injury in sorghum. Heavy rains followed application. Pic via Rick Kochenower.

Brian A.

This article is written by Mr. Cody Daft, Field Agronomist Western Business Unit, Pioneer Hi-Bred

Have you noticed any corn leafing out underground prior to emergence? Have you seen tightly rolled leaves or plants that can’t seem to unfurl leaves and look buggy whipped? Almost all of the fields I have looked at recently have shown these symptoms in at least a portion of the field, and some fields this has been very widespread. The common denominator in all the fields I have viewed has been the herbicides applied were a metolachlor (Dual/Cinch type products) and the weather (cooler than normal, wetter than normal). Similar issues can be noted in grain sorghum to some extent.

The recent wet weather and water-logged soils have increased the possibility of corn injury from many popular soil applied herbicides. Corn growing in wet soils is not able to metabolize (degrade) herbicides as rapidly as corn growing in drier conditions. Plant absorption of herbicides occurs by diffusion. What this means is that the herbicide diffuses from locations of high concentration (application site on the soil) to low concentration (plant roots). The diffusion process continues regardless of how rapidly the corn is growing. In corn that is not growing rapidly (cool, wet conditions) corn plants can take up doses of herbicide high enough to show damage and a few differences in symptomology.

The unfortunate aspect of wet soil conditions is that additional stress is put on the plant not only to metabolize herbicide residues, but also to ward off diseases and insects. These additional stresses can impact a corn plant’s ability to metabolize herbicide.

The most common type of herbicide injury observed under these conditions is associated with chloroacetamide herbicides. These herbicides are used for control of grass and small seeded broadleaf weeds, and are seedling root and shoot inhibitors.

These products include the soil-applied grass herbicides such as:

  • Dual/Cinch/Medal II
  • Degree/Harness
  • Microtech/Lasso
  • Frontier/Outlook
  • Define/Axiom
  • And other atrazine premixes like Lumax (a premix of mesotrione (Callisto), s-metolachlor (Dual II Magnum), atrazine and a safener benoxacor).

What About The Injury Symptoms?

Before corn emergence:

  • Stunting of shoots that result in abnormal seedlings that do not emerge from soil.
  • Corkscrewing symptoms similar to cold/chilling injury.
  • Corn plants and grassy weeds may leaf out underground and leaves may not properly unfurl.

After corn emergence:

  • Buggy whipping – leaves may not unfurl properly.
buggy-whipping syndrom

Figure . Buggy-whipping symptom from carryover of PPO herbicides to corn.via https://www.pioneer.com/home/site/us/agronomy/library/herbicide-carryover/

 

 

What About Safeners?
Products like DUAL II Magnum herbicide contain the safener benoxacor which has been shown to enhance S- Metolachlor metabolism in corn. This enhanced metabolism can reduce the potential of S- Metolachlor injury to corn seedlings when grown under unfavorable weather conditions such as cool temperature or water stress. However, a safener is not the silver bullet, and slow plant growth may still have trouble metabolizing the herbicide even with a safener…but it does help the severity of damage/symptoms.

Will The Plants Recover?
Plants that have leafed out underground or show corkscrewed mesocotyl symptoms are likely to not recover or even emerge from below the soil. Larger plants that are already emerged that show tightly rolled leaves and are buggy whipped will most likely recover once the field sees drier conditions and we have warm weather and sun light to assist in better plant growth.

More Information Discussing Corn Injury From Pre-emerge Herbicides Here:

http://ipm.missouri.edu/IPCM/2009/4/Cool-Wet-Soils-Can-result-in-More-Corn-Injury-from-Preemergence-Residual-Herbicides/

 

Cody Daft
Pioneer Hi-Bred
cody.daft@pioneer.com