In-Furrow Placement of Urea Products with Wheat Seed
Its that time of year I always get the question of “How much urea can I put in the furrow?”. My answer is always two fold first, I wouldn’t recommend it, its a risky venture. Even though I know some do it. Second, my research shows very little is any value from N in furrow. I like P but N just doesn’t show me any return. So for me the process is high risk, with little or no potential for return. But with blog I turn to our purple friend up north to share what their research has sown.
Brian
Guest Authors Kansas State University
Lucas Haag, Agronomist-in-Charge, Southwest Research-Extension Center, Tribune lhaag@ksu.edu
Alan Schlegel, retired
Dorivar Ruiz Diaz, Nutrient Management Specialist ruizdiaz@ksu.edu
To save time and cost, some wheat producers may be thinking about adding a little extra nitrogen (N) as urea or UAN to their phosphorus fertilizer through the drill with the seed. This would either be in addition to, or instead of, any preplant N applications.
While a minimum preplant N application of 20 to 40 lbs N per acre is often desirable, especially in no till production systems, there are risk involved when placing urea containing fertilizers in direct seed contact. Traditionally, we have suggested that no urea or UAN solution be placed in contact with the seed. With the continued adoption of air-seeders a common question we receive from producers is can urea, or enhanced urea products be placed in-furrow.
Methods of early-season nitrogen applications
If the starter fertilizer can’t be “spiked” with urea to add extra N, how can the necessary 20 to 40 pounds of N be applied? Subsurface banding (knifing) of N as either anhydrous ammonia, liquid UAN, or dry product will result in the greatest N use efficiency by the wheat crop. This is especially true for no-till wheat production.
If knifed N applications are not used, the next best application method would be surface banding (dribbling) of UAN solution in streams on 15- to 18-inch centers. Broadcasting urea, ammonium nitrate, or UAN applications are not generally as efficient as subsurface banding, but they are often the best choice due to equipment, logistics, or weed management considerations. Broadcast applications of N will have the most consistent performance if followed by light incorporation, precipitation, or irrigation.
Direct seed placement of nitrogen
When placing starter fertilizer in direct contact with wheat seed, producers should use the following guidelines:
The problem with placing urea-containing fertilizer with the seed is that urea is initially converted to ammonia and may be toxic to plant roots if the wheat seed is placed in direct contact with the fertilizer. Producers may hear of someone who has placed urea in direct seed contact and seemed to have no problems, but there are also many cases where urea-containing N fertilizers has injured the developing seedling and reduced or delayed emergence significantly. The risk of injury is greater in drier soils, at higher soil pH levels, and at higher N rates. High soil pH favors a higher concentration of ammonia as compared to ammonium as urea hydrolyzes. There is significant risk associated with placing urea-containing fertilizers in direct seed contact.
The chart below shows how soil texture affected the level of wheat germination when urea-N was applied with the seed in a K-State greenhouse study. The wheat was well watered in this study, but urea-N placed with the seed still reduced germination, especially in the sandy soil. The readings shown below were taken after 10 days. With the high rates of urea used in this study, it is possible that more damage to the seedlings would occur with time as the urea continues to hydrolyze into ammonia.
Field studies have also shown reduced wheat stands due to in-furrow placement of urea. Across 5 site years in western Kansas the placement of urea in-furrow has resulted in decreased stands at spring greenup compared to the control (Figure 2).
The stand reduction becomes especially noticeable at higher rate of N. One of the challenges of understanding the risk of seedling injury is that the magnitude of injury varies by field conditions an years. In some years very little reduction may be evident, even at higher rates of N, while in other years, stand reductions (and their associated impact on yield) is very evident. As an example at Tribune in 2017, reduction in stand caused by urea placement with seed, and their effect on yield were quite evident (Figures 3 and 4).
Stands were reduced 32 and 63% compared to the control when 30 and 60 lbs of N as urea were applied in-furrow (Figure 3). This resuled in yield reductions of 14 and 40%, respectively (Figure 4).
If you’d like to apply extra N directly in the seed furrow, one option is to use a controlled-release form of N, such as ESN. As shown in figure 4, at N application rates of 30 lbs/ac and less, where ESN-N was applied in-furrow, wheat yields were essentially the same as where the N was applied pre-plant, and higher compared to the same amount of N applied as urea. At the highest rate of application in the study, 60 lbs/ac, even ESN resulted in stand and grain yield reductions.
Also, air seeders that place the starter fertilizer and seed in a band an inch or two wide, or side band the fertilizer relative to the seed, provide some margin of safety because the concentration of the fertilizer and seed is lower in these diffuse bands. In this scenario, adding a little extra urea containing N fertilizers to the starter less likely to injure the seed – but it is still a risk.
Here is a great video by Dr. Haag.
How do you handle your soil sample….
It’s that time of year where wheat producers are in all stages of prep across the state, the graze out folks are wondering when the rains will hit to get the dusted in wheat up and the grain only folks are prepping grain drills or dealing with summer crop harvest. While this blog is focused on the wheat producers it should be acknowledged as a work of caution for anyone who pulls soil samples in environments where the temps during sampling can be above the mid 80’s.
Following some fantastic work by our Wild Cat Soil Fertility Counterparts (see blog) we dug into the same question of how does soil sample handling post collection impact the results. Dr. Ruiz-Diaz results on the impact of storage on nitrogen values was not surprising. But we wanted to go the next step and add in sample bag type.
Our Project
We collected a soil ground and homogenized. Placed in three types of bags Ziploc, Commercial (resin lined paper that is closed) and SWFAL bag (breathable material). Placed samples in a mini-van (Field) and brought a group onto campus (Office). With both sets of samples we had temperature loggers collecting hourly data. Every three days we collected four samples from each location determined moisture content and ran a full spectrum soil analysis including CO2 burst. The soil we used had a OM of 1.1% and soil pH of 6.1
Now let’s back up. Why was the KSU data not surprising. Well for those certified and honorary nitrogen ninjas we understand that the N-cycle processes of mineralization, immobilization, and nitrification are biological reactions which are significantly impacted by soil moisture and soil temperature. But the short and quick version is that the microbes that convert organic N to mineral N (NH4) and convert NH4 to NO3 like warm conditions with good soil moisture. So, when you pull soil samples, hopefully there is some moisture in the soil and then you place it in a bag and seal it. This creates an effective greenhouse environment where moisture cannot escape and is the perfect place for microbes to microbial things. Therefore, you expect the organic cycle and nitrogen cycle to move and move quickly through the processes of mineralization, ammonification, and nitrification.
Back to the data.
First, we have the average daily temperatures from the sitting vehicle and the lab. On days 2-5 the average temp of the van was over 100°, after that the temps dropped. One thing to remember is the temp of the van is an average of a wide-ranging highs and lows between morning and midday while the office temperature being stable throughout the entire day.
What is the most interesting and revealing data may be the soil moisture of the samples. Unfortunately, day 3 samples went straight to the oven, but you can see by day 6 the SFWAL bags (yellow line) had dried significantly while it wasn’t until day 27 did the Commercial bags in the van (Black line w/ triangle) show signs of drying. It’s also important to note that while there are two lines (Field and Office) for the Commercial bags and Ziploc bags, but only one for the SWFAL bags. That is because for all variables measured there was never a significant difference between the SWFAL Field value and the SWFAL Office value.
We are going to start off with the variable that changed the most, NO3-N. This is also the form of N that is measured in most soil test. With a starting point of 3.4 lbs. N ac-1 (based on a six inch soil sample depth) by day 6 the Field samples had jumped to 15.6 lbs. The office samples had much slower increase in NO3 with it taking 9 days to reach 10 lbs. You can also see that the error bars start showing up in the samples after about two weeks. The bars show the range in the sample results of a treatment. The interesting thing we saw was that the location within the van was significant. We set each replication of samples in a different spot in the van, the front seat, middle seat, and rear. The thermometers set with each replications showed that each area of the van had slightly differing temperature, which in turn affected the samples.
Ammonium (NH4-N), which is only reported by a few labs is also impacted by the storage location and bag type, however not to the sample level as NO3-N. Effectively the SWFAL bags and all samples taken to the office maintained consistent NH4 levels. The Com bag and Ziplocs left in the van however saw a significant increase in NH4 over time, basically a 2 lb per day increase.
Of the other measured parameters such as potassium, sulfur, and CO2 burst data were effected. These will be discussed more in depth in a peer reviewed publication and factsheet.
Take Home’s from the Work
While the majority of the nutrients were relatively un affected by the bag type or storage those that are more heavily influenced by organic matter and biological activity where, this includes many of the soil health parameters. The use of SWFAL soil bags resulted in data that was not impacted by storage or time. While most clients of the OSU lab use these bags, more than one samples been brought into the county via a sealed Ziploc baggie. However the majority of the soil samples collected are placed into the resin lined paper bags and sealed. This data set is also important to those who use laboratories that run the Haney test which includes measures of NO3, NH4, Organic N, CO2 respiration and H2O extracted Organic C. It is critical that when using these type of bags that the samples be brought into climate controlled facilities as soon as possible. Its good to remember when looking at the data that the soil we used had a OM of 1.1%, initial NO3 of 3.4 lbs. and NH4 of 14 lbs. A soil with a higher OM% could have even greater change. Another viable is if the soil sample depth is greater than 6”. If your sample depth is 8” then the value is 33% higher.
Questions or comments feel free to reach out via email or social media.
Brian Arnall, Precision Nutrient Management b.arnall@okstate.edu
Chinch bugs are active!
Both Josh Lofton and myself have been talking a lot about the magnitude of chinch bugs we’ve seen this year and the devastation they are having on the crops, both false and true chinch bugs. They have marched through sorghum and now are being found in corn fields. They seen especially bad in failed wheat fields. And in my fields anywhere I had a crabgrass. We are also hearing and seeing a significant increase in blister beetles and stink bugs in soybeans. As a soil scientist all I can recommend is to scout Often, and contact an entomologist or trusted advisor. Kansas State just put out and E-update yesterday with this article from Jeff Whitworth I wanted to share.
Chinch bugs are active in Kansas
Guest Author Jeff Whitworth, Extension Entomologist jwhitwor@ksu.edu
Chinch bugs have historically been a problem in Kansas–in lawns, golf courses, turf farms, etc. But in agriculture, they are mainly a problem in sorghum. However, they can also affect corn and occasionally wheat. Since they are true bugs, chinch bugs may attack any grass where they insert their mouthparts into the plants and suck out the juice. This often has little to no effect on the plant unless there are large numbers of bugs and/or the plants are growing under less-than-ideal conditions so that they are already stressed. Chinch bug feeding simply adds to this stress.
Sampling for chinch bugs the week of July 4 indicated that 95% of the chinch bug population in north central Kansas were adults (Figure 1). Adults don’t feed as much as nymphs but are more concerned with mating, oviposition, etc. This means the majority of feeding in crops (sorghum, corn, etc.) is still to come after the nymphs hatch (Figure 2).
Treating for chinch bugs needs to be accomplished using as much carrier (water) as practical to ensure the insecticide gets good coverage on the plants, including the base of the plants (sprays directed at the base of the plants will help). Nymphs produced now will most likely become adults in 3-4 weeks, then mate and start the process all over again for another generation, which will then move to fall-planted wheat, then on to overwintering sites. They overwinter in bunch grasses then move to wheat in the spring to deposit eggs and start all over again.
Original link https://eupdate.agronomy.ksu.edu/article_new/chinch-bugs-are-active-in-kansas-553-4
To Subscribe to KSU E-update. https://eupdate.agronomy.ksu.edu/index_new_prep.php
Grain Sorghum, 2023 edition
As I sit in my office writing this I am seeing the chances for Stillwater to get a good rain today slowly dwindle away. Last night we had a 75% chance of 0.56. Its now 3pm we have received 0.01 and have a 60% chance of getting an additional 0.10. And as this is how 2023 has gone, but we are still better off than so many west and north of us.
No some of the zeroed out wheat ground and winter fallow ground has seen its first moisture in 100+ days. Planters and drilling are rolling and or ready to roll. So I wanted to throw out a few thoughts and re-share an older blog.
In August of last year I was talking about how the extended drought was impacting organic matter and nitrogen cycling “Nitrogen cycle hiccups and a lot of drying“. Wish I could say things have changed since then but we all now otherwise. While we have moisture to plant and germ our H2O fuel tank is far from full. Its going to take significant rainfall to rebuild the soil profile, not to mention the ponds. And I can not forget how last year we had great rains in May and were going pineapple by the end of July. I had N response studies all over the state in sorghum, at every trial nitrogen was not a limiting factor.
By this point if you know me or have every read anything I have written in the past you should know what is coming. My recommendation for pre-plant N is 0.0 lbs. Go ahead and put a starter down where you have low P or pH that’s out of range, and Fe and/or Zn in the calcareous soils where needed, but that’s it. We are continually adding to the research data base that says sorghum responds exceptionally well to in-season nitrogen applications in some cases nearly all the way to boot stage. I believe we are close to determining/explaining why the crop does so well but not ready to share that work just yet.
I just do not have the trust in the what rains may come to spend money on a fertilization pass that has been proven to be less valuable. Get the seed in the ground and crop up, put out some N-Rich strips. Let the weather play out for a month or so and see 1) Do I have soil moisture to get me through harvest or am I living day by day on a hope and a prayer? 2) is my N-Rich strip showing?
For Question 1) if your living day to day is further investment in the crop warranted? If you have soil moisture and rain in the forecast, its time to rock and roll. For question 2) which I hope you take my advice on doing. If the N-Rich is showing up 30 days into the you can use some rough yield goal estimations and apply 1 lb N per bushel or go get access to a GreenSeeker sensor (available through OSU extension offices) and use OSU’s online calculator SBNRC. If the strips not showing up then you need to consider that a month into the crops growth the soil has supplied 100% of the crops N need. Depending on if you want to push yield or save N adjust your rec accordingly. I would say reducing planned N rate by 40-50 lbs would a legitimate option. There are more and more agronomist utilizing N strips in wheat and sorghum so you could check around.
Final thoughts.
The more I do research on N timing and N management the more I am finding that there are some great benefits to limiting early N availability to the crop. To the point were I am finding and increasing value of an early season N stress on crop performance and grain yield.
Now for rehashed research. Much like wheat, sorghum can and probably should wait for N.
Can Grain Sorghum Wait on Nitrogen? One more year of data.
Original Posting 4.7.2022
Michaela Smith, Ph.D. candidate under advisement of B. Arnall
Brian Arnall, Precision Nutrient Management Specialist
The impressive ability of sorghum to recover from significant N stress with late applied nitrogen was originally reported in the blog “Can grain sorghum wait on nitrogen”. This projected was replicated again in 2021 and these are the results. During the 2021 growing season, frequency of rainfall events and amounts were similar to the 2020 growing season. Figure 1. shows the application dates and rainfall events.
Statistically there was no significant difference in grain yield from the pre-plant (0) and any application up to the 56 day application. This data matches up quite well the yield results from 2020.
Looking and the current soil moisture conditions (Figure 3.) and fertilizer price I think this data supports the recommendation to get the seed in the ground and see how the situation plays out. If there are decent rains at and shortly after planting then there is time to apply nitrogen with little risk of yield loss. If fact the weather during late May and early June provide some of the best chances to getting the fertilizer rained in (Figure 4) . If the weather doesn’t cooperate and provide us the much needed rains, then by waiting to apply we are not left with a lot of Expensive nitrogen setting out in the field of a failed crop.
Final Thoughts Heading into the 2021 Sorghum Planting Season.
– Make sure you have a soil sample, knowing P and K will be critical.
– No need to front load N fertilizer, especially if soil moisture is short.
– Utilize in-furrow P if soil pH and or soil test P is low.
– If you skip pre-plant N APPLY N-RICH STRIPS!!!!
– If you apply pre-plant N consider applying 50% of the expected N or less.
– If you are applying any level of pre-plant N, Create Zero-N Strips.
For more information or questions contact
Brian Arnall b.arnall@okstate.edu 405.744.1722
Special thanks to EDC Ag Products Co LLC for suppling NH4NO3 used in the delayed N project.
Original Post March 22, 2022.
Data for this post available in thesis Impact of delayed nitrogen application in grain sorghum
Smith, Michaela Lynn (2021-05). Available at https://shareok.org/discover
Grain sorghum producers in Oklahoma are challenged greatly by their environment and sporadic rainfall patterns, which diminish as the season progresses. These uncontrollable variables influence timing of nitrogen (N) application and nitrogen use efficiency. Using rainfall events as an incorporation method forces producers to apply before the event regardless of its intensity or delay application until field conditions are acceptable while anxiously waiting for another rainfall event. When deciding to delay N application it’s important to know the effects on physiological development and grain yield.
Trial structure and breakdown
This study was conducted over the 2020 growing season consisting four locations, including one double cropping system following wheat. Ten in-season applications were made using ammonium nitrate (AN) as the N source at a rate of 90 lbs. ac. Using AN as the N source reduced the risk of nitrogen loss through the process of volatilization as the goal of the research was to test the plant not the fertilizer. A pre-plant treatment served as the standard check, while in-season applications were initiated at 21 Days After Planting (DAP) and applications made sequentially at 7-day intervals. A non-fertilized check was included to the study to confirm locations were responsive to N fertilized applications Hybrid, plant date, and seeding rate can be found in Table 1.
Physiological Response to Application Timing
Two of the four locations demonstrated an effect to physiological development and maturity with the delay of nitrogen application. A delay in heading by a one to two-week period was observed at Perkins and Lahoma for applications made after May 21st (Table 2.). This delay in heading contributed to similar delay in maturity and potential harvest date. At Perkins decreased plant height was observed in the pre-plant plot and was associated with the onset of late season nitrogen deficiency (Figure 2). While this response was unexpected, the impact of nitrogen deficiency experienced early in the crop growth on the root and shoot growth has been well documented in many species. As a plant experiences nitrogen limitations growth changes from above ground to the below ground parts (roots) in an attempt to alleviate nitrogen stress. This increase in root growth could contribute to a more efficient uptake of nitrogen and decrease loss. In contrast to Figure 2, pre-plant application is shorter than compared to later season applications, this could be a result of inadequate N uptake thus leading to N loss by leaching, whereas later applications had increased root growth for efficient N interception and uptake.
Yield Response to Application Timing
Response of N was observed at all locations (Figure 3), while the delay of nitrogen varied in its effects across all locations. Grain yield from each N application was compared back to the pre-plant application to evaluate the effects of timing. All four locations responded positively to N fertilizer. At both LCB and Lahoma grain yield was maintained with applications made as late as 42 to 63 DAP respectively before any negative trend in grain yield was observed. Perkins was the only locations to have a statistically significant increase in grain yield due to delayed N applications. At this site, which is a sandy loam, waiting until 42 DAP resulted in a 15 bushel increase over the pre-plant plot. Now Alva which was double crop showed that rainfall is key. At this site, none of the in-season treatments made it up the level of the pre-plant. The reason for this will be discussed further below.
Influence of Rainfall
The loss in grain yield at Perkins in the pre-plant application could likely be reflective of nitrogen loss due to leaching. Pre-plant applications have been well documented in the aspect loss as a result of crop requirement and early physiological development. Long term mesonet rainfall data depicts a decline in the probability of rainfall with the progression of the growing season across all locations. In early season the probability of 0.5 inches of rainfall ranges from 8 to 10% respectively for LCB, Lahoma, and Perkins, and dramatically decline to percentages at low as 5% in mid-July during grain filling period. For Alva rainfall probability is substantially lower as its season was initiated during the drier months, which depicted a probability of 6% for 0.5 inches of rainfall, and 4.5% for 1 inch for early season rainfall crucial for pre-plant incorporation and crop establishment. These probabilities drop considerably compared to regular season as the months progress onward, mid to late August probability for 0.5 inches ranges from 0.8 to 11.5%, while for a 1 inch is 0 to 6.9%. Past weather data provided by the mesonet illustrates how later in the season rainfall and its amount is variable, suggesting that in a double crop scenario delayed application is not recommended while it is in regular season crop due to the increased chance of rainfall probability.
Summary
The purpose of this study was to evaluate the impacts of delayed nitrogen application in grain sorghum. In order to develop an accurate conclusion additional site years are required, although current data could suggest delaying nitrogen application for full season grain sorghum is possible without a detrimental loss in grain yield. This means producers have time to evaluate the crop and market to determine if more inputs are needed and economical, while allowing implementation of technologies such as the N-Rich Strip and SBNRC.
If you have any questions for comments please reach out.
Brian Arnall
b.arnall@okstate.edu
405.744.1722
Acknowledgement of EDC Ag Products Co LLC for support of this project.
Mechanics of Soil Fertility: The how’s and why’s of the things.
Ag Lime
The primary purpose of Ag lime is to increase to soil pH so before we talk ag lime, we need to talk soil pH. pH, regardless of what is being measured pH is the – log H+ ions. So how many followed that! Basically liquids, we are measuring the soil solution, are made up of a ratio of hydrogen (H+) cations and hydroxide (OH-) anions. When the two are at a even balance pH = 7. When OH– out number H+ pH is greater than 7 (basic) and when H+ out numbers OH– , the pH is less than 7 (acidic). When you send a soil sample off to the lab the most basic test preformed is pH. There are a few methods to do this but at Oklahoma State we take 10 grams of your soil and add 10 mls of water, stir it and record the pH with a probe. This pH reading is measuring the amount of H+ that is present in the soil solution, basically the H+ not attached to the soil, this is called active acidity. However, the amount of H+ in the soil solution is 1/100th the amount adsorbed on cation exchange sites. And if we want to change the pH we have to account for the H+ in the solution and the H+ that is on the exchanges sites. These H+ on the exchange sites will quickly pop off the CEC when the concentration of H+ in the soil solution is decreased. That is why when the pH is below a critical point the lab will run a buffer analysis. Think of it in this way, the lab adds what is equivalent to one ton of pure lime per acre to the cup, mixes well and re-measures the pH. The lab is looking to see how much the pH changes. Say there are two soils which both started at a pH of 4.3 and after the buffer solution was added with the first soil the pH changed to 6.7 while the second changed to 5.1. This tells us the second soil had a significantly greater amount of H stored on the CEC and therefore will take a lot more lime to change the pH in the field. Just a side note more than likely soil 1 was sandy, low CEC soil while soil 2 and fair amount of clay and significantly higher CEC. Therefore, we use the buffer index not the soil pH to make a lime rate recommendation.
Now that you have had a crash course in the chemistry of pH lets jump off the deep end of chemistry and talk Ag Lime. Ag lime is the short name for ground limestone used to change the soil pH of a field, garden, or lawn. We work heavily with calcitic (CaCO3) and dolomitic (MgCO3) lime. Both limes are basically a cation, calcium or magnesium, and a carbonate. The combo of a cation and carbonate is the winning ticket for pH change. However, many tend to think the cation is doing the work. Which is not true, if it was, we would be using gypsum (CaSO4) as the primary source of Ag lime, because it is slightly more soluble than limestone. {Side note sulfate (SO4) has already been oxidized and has no effect on pH, decreasing or increasing.} The cation does play an important role as its purpose is to kick the H+ off the soil particle. But removing H+ is easier said than done. Below is the lyotropic series, this represents the strength that cations are held to the CEC. Note the Al3+ and H+ is at the top of the list, meaning if all cations are present in equal amounts the Al3+ and H+ will bind to the CEC before any other.
Al 3+ = H+ > Ca 2+ = Mg 2+ > K+ = NH4+ > Na+
The one way the lyotropic series can be beat is by overwhelming the soil system with a cation lower on the list. In other words, we can put large quantities of Ca2+ and Mg2+ into the soil and they kick the H+ off the CEC. This is critical because the pH can not be changed unless the H+ enters the soil solution. This is where the CO3 does the heavily lifting of raising the pH. The CO3 reacts with H+ in the soil to form H2O and CO2.
2H+ + CO2 -> H2O + CO2
So, the amount of lime that the soil test recommends you apply is based upon the amount of H+ in the soil solution and on the soil CEC that needs to be neutralized to increase the pH to the desired level. Typically, these recommendations are made assuming a 6” incorporation depth, so that means we need to apply enough CO3 to neutralize the H+ in and on the two million pounds of soil.
Below are two Sun-up videos where I discuss soil pH and lime.
If you have any questions or comments please feel free to reach out. b.arnall@okstate.edu
Jan 2023 edition of Wheat N management.
With the recent weather and lack of pre-plant N applied this fall I know a ton of rigs are running right now and I am handling a lot of questions about N rate, source, and time. So, while it might be a bit late I wanted to share a few thoughts.
First soil N: If you look back at the August 22 Blog, A Hiccup in the C cycle, well that cycle was put up on blocks for most of the wheat belt will late Oct. This had multiple ramifications, one; the summer crops suffered, two; mobile nutrients moved to the surface, and three; residue did not break down due to lack of moisture, the residue breakdown in turn ties up N into OM. These factors all resulted in above average soil test NO3 values. However, as I mentioned in that blog when the soils get moisture and warm temps that break down will ensue and short-term plant available N will drop until the OM mineralizes and releases NH4 sometime in the spring.
Second soil water: For most of the wheat belt the Mesonet is showing a concerning trend in soil moisture. The 16” soil moisture map looks pretty good with exception of the panhandle. However, if you look at the difference between the 16” and 36” you can see there is not a lot of moisture at depth. If we maintain these warmer temps the crops going to keep growing and burning through the moisture. Our ground is going to require a good dose of spring rains to maintain the yield potential.
If you have read much of my work you know my opinion, supported by years of research, on nitrogen timing in wheat. In my perfect scenario I go with a in-furrow application and then hold off on any additional N application until just ahead of hollow stem for wheat under the 75-bushel range. And for anything over that yield level I like a shot of 30-50 at green-up with the remaining at jointing. With both approach I am utilizing reference strips. This timing approach allows for adjustments, which I believe this season will be needed.
So for me the trick with this season to maximize profit will be the flexibility. Going all in early locks you down. For those who haven’t applied yet but are about to, you should consider adding a zero N check or two. The zero N will help you see if all that residual N is still there for if the organic matter cycle has tied it back up. Basically, if the zero N shows early, that means your crop is dependent upon you for its N needs. If you get to hollow-stem and that zero N is still not visible, Pull Back the Reins on fertilizer N, the system is providing a fair amount. In the Arnall Utopia, the N you don’t apply in the Zero can go elsewhere and now you have a N-RICH Strip. With both of these options we can figure out a N rate based on GreenSeeker readings. If you have interest in applying reference strips let me know, I am happy to help create the applicator files that are used in the fertilizer rig.
Of course if your fertilizer management plan is in a holding pattern, the now is a perfect time to apply your N-Rich Strip. I have several blogs and extension materials which help describe the process N-Rich Blog.
If you’re going to go without the reference strip, then I say hold the majority of the N until we do or do not get spring rains. If it rains, let her rip. If not your probably sitting better with the N not on the field. Take a few lessons from the last wheat crop, heavy N was often more of a problem than being short on N when we were so dry.
Questions or comments feel free to reach out via email or social media.
Brian Arnall, Precision Nutrient Management b.arnall@okstate.edu
Related Blogs
Did in-furrow starter products increase yields?
Bronc Finch, Precision Nutrient Management Post-Doctorial Scientist.
Brian Arnall, Precision Nutrient Management Specialist.
As winter wheat planting time approaches this question arises often when fertilizer decisions are being made. There are several products that have been marketed to wheat producers that contain combinations of nitrogen (N), phosphorus (P), and potassium (K) as well as some plant essential micro-nutrients. These products are designed to be placed with the seed as an in-furrow application at planting and provide nutrients earlier in the season than traditional dry spreading methods. While the state of Oklahoma macro-nutrient deficiencies are often corrected with traditional fertilizing methods and micro-nutrient deficiencies are not commonly witnessed in winter wheat; these products are often sold with the expectation yield increases can still occur. This has led to the question can these fertilizer products improve winter wheat yield production regardless of soil analysis results? To answer this Oklahoma State University developed a study evaluating eleven different starter fertilizer options available to producers (Table 1). Of these eleven fertilizer options three are commonly available fertilizers, and eight of them are products available through specific companies. The study was carried out at three locations a year for two years.
To compare the ability of these products to increase yield beyond the recommendation of soil test results, pre-plant soil samples were collected to a 6-inch depth at each of these research sites. Soil analysis of the five-site years used in this evaluation (Table 2) reported no deficiency at the Lake Carl Blackwell research farm. Deficient concentrations of P (< 32.5 ppm) was recorded at the North 40 research site and Perkins research station, along with a low pH (4.8) at the Perkins research station. Acidic soils are of concern for crop production having many detrimental impacts to root production, however there is also influence on nutrient availability. Aluminum concentrations are often higher in low pH soils which will result in root pruning and the binding of applied P, increasing the concerns when soil analysis P concentrations are already deficient.
Evaluation of these commercially available products at non-nutrient deficient sites show no influence of any in-furrow placed fertilizer product on winter wheat grain yield compared to an unfertilized check, yielding an average of 52 bu ac-1 in 2014-2015, and 93 bu ac-1 in 2015-2016 (Figure 1). Figure 1, along with the following figures, show the mean and variability of winter wheat grain yield of each of the commercially available starter fertilizer product treatments, as well as the check treatment which received no fertilizer application. The column for each treatment represents the grain yield in bu ac-1 which is the average of three replications the variability of grain yield at an individual treatment can be observed by the error bars which depict the range of grain yields within a specific treatment. The larger the error bar the less consistent the yield and the harder it is to separate out statistical differences in yield.
When the soil test P level was below 32.5 ppm, some P containing starter fertilizers where able to increase winter wheat grain yield in 2014-2015 growing season at North 40. Products containing 40 – 52% P; MAP, DAP + Awaken and MES-Z, improved grain yield by up to 14 bu ac-1 compared to the check. At the North 40 locations APP did not show the same increase in yields as DAP and MAP. The addition of micro-nutrients by Awaken combined with DAP yielded a 20 bu ac-1 increase over Awaken used alone, but no increase compared to DAP or MAP used alone. Similarly, the addition of Zinc by MES-Z yielded similar to the base product, MAP.
When P deficiency was compounded by a low pH such as observed at Perkins there was response to more in-furrow products. Compared to the check, increases up to 32 bu ac-1 in winter wheat grain yield was found by DAP, MES-10, MES-Z, Nachurs + CornGrow, and DAP + Awaken. Further investigation revealed the source of P fertilizer (DAP, MAP, and APP) reported no difference in yield averaging 55 bu ac-1. The addition of S and K by Nachurs was not different from APP, which is a similar liquid fertilizer, averaging 52 bu ac-1. Micro-nutrient additions by Awaken combined with DAP (56 bu ac-1), and by CornGrow combined with Nachurs (56 bu ac-1) did not increase winter wheat grain yield compared to each other or their respective base products of DAP (59 bu ac-1) and Nachurs (53 bu ac-1). Similarly, additions of S by MES-10 and S and Zn by MES-Z yielded similar to one another with 65 and 72 bu ac-1respectively but produced 14 bu ac-1 more yield on average than the base product MAP. At Perkins, which is a well-drained sandy loam soil, we often see a yield response to S when yield levels so seeing a response to the products that added 7 lbs of S, was not un-expected.
With these results in mind and the current cost of fertilizers, the addition of fertilizer products on non-limiting soils is not expected to result in an increase in winter wheat grain yield. Also, many of these products contain micro-nutrients that are rarely found to be at deficient levels for much of the winter wheat production region in Oklahoma. Therefore, the use of these products on non-nutrient limiting soils would unnecessarily increase the cost of production and decrease the return on investment. However, that is not to say these products should be avoided completely, in the event of a nutrient limiting soils some products show potential benefit for correct soil deficiencies. As observed some P containing products were able to provide adequate P concentrations for increasing yields and overcoming low pH conditions. This work along with previous work evaluating efficient fertilizer management suggest the correction of a nutrient deficient soil to be more important than the source of the nutrients and supports the need for soil testing and following recommendations.
This blog is a summation of Mr. Jonathon Williams thesis which was published in the Journal of Agricultural Sciences. Impact of in-furrow fertilizer on winter wheat grain yield and mineral concentration https://doi.org/10.1017/S0021859622000557
SIDEBAR
So we do small plot research to me in control of as many variables as possible. But all farmers and consultants know that fields are are variable and the results of small plots do not always translate well. I get that 100%, but for me as a scientist I need to understand the little things so that I can apply the knowledge on a large scale. Just last month I wrote a blog about cutting phosphorus rates BLOG. The third major take home of the blog was:
A composite soil sample is an AVERAGE of the field. If your average is right at the ok level (pH of 5.6ish and M3P of 30 ppm), then half of your field is below optimum and will benefit from P.“
That applies to what we learned from the above study. We found if soil test said nutrient was adequate we did not see a response of adding more. However if we combine the two blogs, if your composite soil test comes back just at the optimum level, there is a good chance at least 45% of field is below optimum and may respond.
So guess what my recommendation is. Soil SAMPLE, do it right (proper method and core numbers) and do it at the highest resolution you can afford, at least once.
Finally Do Not Skip on Nutrients when soil test says there is a need.
BA
Any questions or comments feel free to contact me. b.arnall@okstate.edu
Soil sample handling practices can affect soil nitrate test accuracy
From Guest Authors,
Bryan Rutter, PhD student and Soil Testing Lab Manager, Kansas State University
Dr. Dorivar Ruiz Diaz, Soil Fertility Specialist, Kansas State University
The accuracy of a soil test is limited, in part, by the quality of the tested sample. For this reason, strong emphasis is placed on ensuring representative samples are collected in the field. However, these samples must also be handled properly after they have been collected.
Soils are home to a diverse population of microorganisms, many of which help decompose crop residue and cycle nutrients in soils. This nutrient cycling is crucial for crop production, but can skew soil test results if it continues in soil samples after they have been collected.
Microorganisms drive the soil nitrogen cycle
The nitrogen (N) cycle in soils is particularly complex and is strongly influenced by microbial activity and, therefore, temperature and soil moisture conditions. Bacteria and fungi consume organic material and use carbon as an energy source. During this process, N contained in the organic matter undergoes several transformations, ultimately converting it to ammonia. This conversion from organic-N to inorganic-N (NH4+, ammonium) is called “mineralization.” Plants can then take up the ammonium (NH4+), or converted to nitrate (NO3–) by certain bacteria through a process known as “nitrification”.
The microbial activity requires moisture and heat, and the processes described above happen more quickly in warm, wet soils than in cold, dry soils. Microbial activity does not stop just because a sample has been collected and put in a bag. This activity continues as long as the environmental conditions are favorable. As a result, soil tests for plant-available N have the potential to change substantially if samples are not handled properly. This is an important consideration for growers because these soil test results are used to determine the profile-N credit and, ultimately, adjust N fertilizer recommendations.
Research study on soil sample storage
A recent study at the K-State Soil Testing Lab illustrates what can happen if sample submission is delayed. For this study, soil was collected from the Agronomy North Farm (Manhattan, KS) and thoroughly mixed/sieved to homogenize the material. This soil was then placed into sample bags, which were randomly assigned to different combinations of storage temperature and duration. One set of samples was kept in a refrigerator while the other set was kept in a cargo box in a truck bed. To monitor changes in soil test levels over time, three sample bags were removed from the refrigerator and truck box every two days (48 hours) and tested in the lab.
Figure 1. Change in soil test nitrogen parameters over a 14-day storage period. Samples stored in an unrefrigerated cargo box are indicated by purple points. Samples stored in a refrigerator (38F) are indicated by grey points. Graphs by Bryan Rutter, K-State Research and Extension.
Take home points from the K-State Soil Testing Lab study:
- Mineralization and nitrification led to more than a 3x increase in soil test nitrate in the undried and unrefrigerated “Truck Cargo Box” samples (purple points in Figure 1).
- Soil test nitrogen did not change substantially in refrigerated samples.
- Profile-N credits calculated from soil test N results were nearly 100 lbs of N/acre higher for the unrefrigerated samples (Figure 2).
- Improper handling and storage of soil samples can dramatically reduce soil test accuracy and may lead to under or overfertilizing crops.
K-State Soil Testing Lab Recommendations
- Submit soil samples to the lab as soon as possible, ideally on the same day they were collected.
- If same-day submission is not possible, samples should be air-dried or placed in a refrigerator set at 40 degrees F or less.
Please see the accompanying article “The challenge of collecting a representative soil sample” for guidance on field soil sampling practices.
For detailed instructions on submitting soil samples to the K-State Soil Testing Lab, please see the accompanying article “Fall soil sampling: Sample collection and submission to K-State Soil Testing Lab”.
For detailed information on how N credits are calculated please see the MF-2586 fact sheet: “Soil Test Interpretations and Fertilizers Recommendations”.
Bryan Rutter, PhD student and Soil Testing Lab Manager
rutter@ksu.edu
Dorivar Ruiz Diaz, Soil Fertility Specialist
ruizdiaz@ksu.edu
The original article can be found on the KSU Agronomy E-update site
https://eupdate.agronomy.ksu.edu/article_new/soil-sample-handling-practices-can-affect-soil-nitrate-test-accuracy-511-4
Phosphorus decisions, Is it worth cutting P?
With the current conditions and input cost many wheat producers are considering cutting back on inputs. I can’t disagree with the plan, but I would caution against what you cut. If you have read any of my past blogs, or seen me speak, you should know I’m all for cutting back on pre-plant nitrogen (N). Based on some recent trials I would not argue cutting the potassium (K) side, but phosphorus (P) that’s another story that we will walk through in this blog.
First and foremost, soil testing is the key to P management. If your soil test is below the critical threshold for the test you use, 32.5 for Mehlich 3 (M3P), then you need to add phos. We have enough work that shows current recommendations work for P in wheat. Reeds paper Evaluation of incorporated phosphorus fertilizer recommendations on no-till managed winter wheat Link to Paper goes over soil test recommendations in no-till and the recent double crop soybean project Double Crop P and K Blog highlights the importance of P fertility, regardless of yield level. Also if your soil test is below a 5.5 and you haven’t limed (Liming is the best solution, Band-aids not so cheap Blog ), then the next best option is adding additional P to alleviate the aluminum toxicity Band-aids for low pH Blog. In-short if the fields soil test P and or pH is below optimum you should not forgo P application.
But the primary reason I am writing this blog is for those looking at fields with composite soil test that is right around the critical thresholds, and they are trying to make the call on to apply P or not to apply P. Even on fields with soil test values in the good level, I am usually in favor of banding in-furrow fertilizer wheat, but not because of the same reasons I am for corn. With corn you are planting in cool soils and the availability of nutrients like P is lower in cool wet soils. For wheat cold soil isn’t the concern until we reach the end of the planting window. It will serve as a bit of a “pop-up” as the crop comes out of dormancy in the spring. I have also seen little to no value of N applied in furrow. I see same response to DAP (18-46-0), MAP (11-52-0), and TSP (0-46-0) when all applied at same rate of P. Meaning it was the P not N making the difference.
For me the reason I still recommend getting a little phosphate out even when the soil test comes back is that the great majority of fields have a large range of variability. Looking at a set of 650 grid sampled fields across Oklahoma and Kansas it showed on average soil pH 6.0 and M3P was 34 ppm. Both pH and P are at adequate/optimum levels. However, the average is usually somewhere between the low and high point and in this data set and the range of soil pH was 1.8 units and the range in M3P was 67 ppm. That meant on average of the 648 field with pH values the average difference between low pH and high pH was 1.8 units and the difference between low P and high P was 64 ppm.
The field below is from Kingfisher county and was sampled at a resolution of 10 acres per sample. This is a fairly course resolution for grid sampling but provides a great view of how variable our soils can be. The field average pH is 5.3, which is below optimum but our aluminum tolerant wheats would be able to handle fairly well. For the P the average is 22 ppm which needs about 18 lbs of P2O5 to max yields. If the farmer applied a flat rate of 20 lbs there would be significant forage loss on about 65% of the field, for grain only about 45% of the field due to underapplication of P. Note that low P and low pH are not correlated well, meaning the areas low in pH are not always low in P.
Banding P makes it more efficient because it slows the rate of tie. However, we have plenty data that says broadcast applied P is still a great option, even after planting. So what are my take homes from this blog?
First: If you are grazing wheat get down 40-50 lbs of N pre. But I have plenty of data the pre-plant N on grain only wheat is not needed. I have the same amount of data that shows the only value of in-furrow N for grain only is that it forces you to plant more seeds, because it just lowers stand.
Second: When it comes to wheat pay attention to Phosphorus and soil pH. Even our acid tolerant wheats preform better in neutral soil pHs, especially forage wise.
Third: A composite soil sample is an AVERAGE of the field. If your average is right at the ok level (pH of 5.6ish and M3P of 30 ppm), then half of your field is below optimum and will benefit from P.
Fourth: If you can band P great, but if you cant broadcast is still a viable option. Do Not Skip P when soil test says there is a need.
Questions or comments please feel free to reach out.
Brian Arnall b.arnall@okstate.edu
Impact of Nitrogen timing 2021-22 Version
Raedan Sharry, Ph.D. Student Precision Nutrient Management
As wheat planting rapidly approaches for some and gets underway for others, it is without a doubt worth considering the current moisture conditions, the near-term outlook, and how that might influence N management decisions. There is plenty of information located in this blog and many other resources that show the benefits of delayed N management in crops. This is particularly true when considering an extremely long growing season for winter wheat in the southern plains. Given our current soil moisture situation yield expectations given the current soil moisture may be limited until replenishing precipitation occurs. This has many questioning their N management plan.
Often when talking about the past N timing results How Late Can You Wait there are comments about the risk of waiting and the crop needing N to get going. Most of the work in the past looked at a single application of N applied at different times and didn’t address split application. But the data from a couple of trials located at Perkins and Perry Oklahoma in the 21-22 season is reinforcing what the past data suggest. These trials consisted of 2 varieties with a 0 N check and 9 combinations of N timings to at 90lbs rate and 3 timings at 140 lbs. of N. Ammonium nitrate (34-0-0) was the N source used in this study to limit the impact of urea volatilization. For both locations we have pre-plant soil test results for the 0-6 and 6-12 inch depths. Both locations at about 30 lbs of total N and OM of 2.0% in the top 6 inches.
The varietal component of this study doesn’t matter in this context so we will leave them unnamed as both cultivars responded very similar to nitrogen timing and rate within each location. The first thing to highlight is both trials were sown in mid-October. October 19th and October 21st to be exact. Both locations received timely rainfall to start the season with approximately 1.5 inches of precipitation falling in half-inch increments between October 25th and November 10th. Top-dress applications in January and March were made on 1/10/22 and 3/24/22 respectively. After the early rainfall events the season was largely dry up until the precipitation in mid-march. So pre-plant fertilizer was incorporated in a fairly timely manner however the January application was applied almost a month before meaningful precipitation occurred. The March application missed the only productive rainfall event until the end of April however this occurred solely due to the application trigger being based on reaching the jointing stage.
If we take what is stated above into consideration it would be hard to imagine that January applied N would provide a boost over pre-plant. The data says different. At both locations pre-plant N cost us bushels compared to treatments containing fertilizer only in January. Even splitting the application did not produce the same result as treatments that only apply N in-season. At the Perry location at the 90 lb. total rate there was no yield difference between any split applications and the 0-90-0 application making the January application more cost effective. While there were no split application treatments made at the 140 lb. rate the 0-140-0 treatment (140 lbs. applied in January) maximized yield. I also think it is important to note that if the March applications would have been applied prior to the rain event immediately preceding them the March application likely would have AT LEAST been competitive with the other treatments given previous research focusing on delayed N applications. Statistically the 90-0-0 and 0-0-90 were in the same grouping for both cultivars.
At the Perkins location the results were not much difference as far as impact of timing. In-fact except for Var 1 at Perkins 0-140-0 was statistically better than all other treatments. Also expect for Var 1 at Perry the 0-90-0 and 140-0-0 were statistically the same. In all cases 90-0-0 yielded less than 0-90-0 but it was not statistical for all comparisons.
The timing component is important as it shows that we are perfectly capable of applying N in-season and being successful. In-fact this work, and other work is starting to show that contrary to past beliefs, split application is not providing any benefit over a single well-timed application. The source of N of this project needs to be consider as the January top-dress application sat on the surface for almost a month before finally receiving just under two-tenths of an inch of precipitation. We will have another blog coming out soon looking at the impact of N sources urea versus UAN when applied in Fall, January, or March very soon.
With these results in mind and current moisture conditions it is only reasonable to consider delayed nitrogen application, not only to increase nitrogen use efficiency and possibly increase yields as well as a virtually guaranteed increase in grain protein, but also as a way to hedge your bet against fertilizer application cost. This work and all the past work support that grain only wheat does not benefit from the application of pre-plant N. By applying N fertilizer now there is a chance that it may become a sunk cost with a poor performing or even failed crop. And if it does start raining, well that pre-plant N will be right there ready to be leached. Being efficient is important in the tight years, and by delaying N application until you are sure the crop requires it may save you a pretty penny or more.
Questions or comments please feel free to reach out.
Brian Arnall b.arnall@okstate.edu
Acknowledgements: EDC Ag Products Co LLC for support of this project.
Oklahoma Wheat Commission and Oklahoma Fertilizer Checkoff for Funding.
Latest Posts
-
In-Furrow Placement of Urea Products with Wheat Seed
Its that time of year I always get the question of “How much urea can I put in the furrow?”. My answer is always two…
-
How do you handle your soil sample….
It’s that time of year where wheat producers are in all stages of prep across the state, the graze out folks are wondering when the…
-
Chinch bugs are active!
Both Josh Lofton and myself have been talking a lot about the magnitude of chinch bugs we’ve seen this year and the devastation they are…
-
Grain Sorghum, 2023 edition
As I sit in my office writing this I am seeing the chances for Stillwater to get a good rain today slowly dwindle away. Last…
Down and Dirty with NPK 