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OSUNPK Fertilizer Market Outlook: Nitrogen Decline Pauses 9.7.26
The most important fertilizer-market development of the past two weeks is not another sharp price move, but the pause that followed August’s nitrogen decline. Oklahoma’s September 4 report shows urea down only $4.40 per ton, UAN 32% down $5.72, and anhydrous ammonia down $5.00. UAN 28%, phosphate, potash, AMS, and ATS were unchanged. Looking back four weeks, however, the nitrogen correction remains substantial: urea is down 6.6%, UAN 28% is down 8.7%, UAN 32% is down 5.7%, and NH3 is down 5.8%.
Price-source note: The accompanying graphic’s Oklahoma average, minimum, and maximum come from the USDA Agricultural Marketing Service Oklahoma Production Cost Report. USDA does not identify contributing dealers. Named public dealer cash quotes, including Two Rivers Cooperative, are tracked separately and are not blended into USDA statistics.
USDA attributes the quiet local market to weak demand under persistent heat and drought. That distinction matters. Stable prices caused by limited field activity do not necessarily indicate that replacement costs or global supply risks have settled. As fall demand develops, local bids may respond differently depending on dealer inventory, transportation, and when replacement tons were purchased.
Nitrogen markets continue to balance large international buying programs against improved availability. In recent public commentary, StoneX fertilizer analyst Josh Linville pointed to India’s 1.7-million-ton urea purchase and identified Brazil as the next major demand cycle to watch. A completed Indian tender can absorb prompt supply, but the next direction depends on whether Brazilian demand arrives strongly enough to keep exporters engaged. Product type also matters because Brazil typically needs granular urea, while much of China’s available export supply has been prilled.
Phosphate remains a different story. Oklahoma DAP and MAP prices were unchanged, but the global market still carries support from restricted Chinese exports and elevated sulfur and ammonia costs. Linville also highlighted the arrival of Moroccan phosphate cargoes following the suspension of U.S. countervailing duties, including an MAP vessel that is more relevant to U.S. demand than the earlier TSP shipment. Additional import competition could improve availability, but one or two vessels do not by themselves reset the market.
Sulfur is part of that phosphate equation. It is required to manufacture phosphoric acid, so constrained sulfur trade can support DAP and MAP production costs. The same global pressure does not translate directly into identical local movement for AMS and ATS; both remained unchanged in Oklahoma this period. Those products should therefore be evaluated on actual sulfur need, formulation, and local cash price rather than assumed movement from phosphate headlines.
The next items to watch are Oklahoma rainfall and fall field activity, Brazilian urea purchasing, additional Indian tenders, Chinese export volumes, Moroccan phosphate arrivals, sulfur availability, and inland freight. These forces remain capable of moving in opposite directions, so the current pause should not be read as a firm price forecast.
For Oklahoma producers, this is a good time to compare products on both dollars per ton and cost per pound of the needed nutrient. Quotes should be placed on the same pickup or FOB basis, with application, blending, delivery, and tax separated before making comparisons.
Fertilizer markets, local prices, and availability can change quickly. Confirm current prices and terms with local dealers before purchasing.
Market Sources
- USDA Agricultural Marketing Service. Oklahoma Production Cost Report, September 4, 2026. https://www.ams.usda.gov/mnreports/ams_3621.pdf
- Josh Linville, StoneX. Public fertilizer-market commentary on India’s urea tender, Brazil’s demand cycle, and Moroccan phosphate arrivals. https://www.linkedin.com/posts/joshua-linville-9555a711_indias-urea-tender-just-gave-a-fading-rally-activity-7488273113961476098-Mepg
- CoBank. Why Higher Fertilizer Prices Are Here to Stay, August 13, 2026. https://www.cobank.com/knowledge-exchange/why-higher-fertilizer-prices-are-here-to-stay
- World Trade Organization. Fertilizer Trade Impacted by Strait of Hormuz Conflict, July 10, 2026. https://www.wto.org/english/blogs_e/data_blog_e/blog_dta_10jul26_451_e.htm
This report is produced via Chat GPT Plus Work, with review by Brian Arnall.
OSUNPK Fertilizer Market Outlook: Local Nitrogen Prices Break Lower 8.24.26
The most important movement of the past two weeks is the decline in Oklahoma nitrogen references. From August 7 to August 21, UAN 28% fell $39.70 per ton, urea fell $38.73, and anhydrous ammonia fell $46.00. USDA attributes the weakness to reduced demand as persistent heat and limited rainfall constrain field activity across the state.
Price-source note: The accompanying graphic’s Oklahoma average, minimum, and maximum come from the USDA Agricultural Marketing Service Oklahoma Production Cost Report. USDA does not identify its contributing dealers. Named public dealer cash quotes, including Two Rivers Cooperative, are monitored separately and are not blended into the USDA statistics.
The local decline does not mean that global nitrogen risk has disappeared. StoneX reported August 19 that India secured about 1.7 million metric tons in its latest urea tender with ample offers, including an expected contribution from China. That supply response eased immediate pressure, but attention now shifts toward Brazil’s September-through-December import window. Brazil needs granular urea, while much of China’s available export supply is prilled, so timing, product form, and destination still matter.
Josh Linville’s August 12 market commentary likewise described a well-supplied Indian tender and a weaker NOLA urea market, while cautioning that UAN and ammonia manufacturers held strong forward sales books. That distinction matters in Oklahoma: a softer urea benchmark can move faster than UAN or ammonia when producers have already covered substantial forward demand. Local weather can amplify the difference by weakening spot demand even while manufacturer positions remain supported.
Phosphate prices were nearly unchanged in the Oklahoma report, but their cost structure remains exposed to ammonia and sulfur. CoBank noted August 13 that Middle East disruptions and Russian supply constraints have affected ammonia production and sulfur availability, while China’s phosphate exports remain sharply restricted. Linville also highlighted sulfur as a bottleneck because a large share of globally traded sulfur normally moves through the Strait of Hormuz. Those pressures can raise the cost of producing DAP and MAP even when local posted values are temporarily steady. They also deserve attention for AMS and ATS, although Oklahoma’s reported averages changed little this period.
Potash remains the quietest major nutrient. Its production base is less directly tied to Middle East natural gas and sulfur, although ocean freight and broader logistics can still affect delivered replacement costs.
Over the next several weeks, watch Oklahoma rainfall and fall field demand, Brazil’s urea buying pace, the mix of Chinese exports, further Indian tenders, phosphate operating rates, sulfur availability, and freight. These forces point in different directions, so the current local nitrogen decline should be read as a market development rather than a definitive forecast.
For Oklahoma producers and dealers, the practical step is to compare current cash quotes on the same pickup or FOB basis and separate material price from delivery and application. Soil-test needs and product fit should remain central; price movement alone does not determine the best nutrient plan.
Fertilizer markets, local prices, and availability can change quickly. Confirm current prices and terms with local dealers before making purchasing decisions.
Market Sources
- USDA Agricultural Marketing Service. “Oklahoma Production Cost Report,” August 21, 2026. https://www.ams.usda.gov/mnreports/ams_3621.pdf
- StoneX. “Brazil’s Urea Import Window Now Decides Where Global Tonnes Land Next,” August 19, 2026. https://www.stonex.com/en/insights/brazil-s-urea-import-window-now-decides-where-global-tonnes-land-next/
- Hoosier Ag Today. “Josh Linville: Fertilizer Markets,” August 12, 2026. https://www.hoosieragtoday.com/2026/08/12/josh-linville-fertilizer-markets/
- CoBank Knowledge Exchange. “Why Higher Fertilizer Prices Are Here to Stay,” August 13, 2026. https://www.cobank.com/knowledge-exchange/why-higher-fertilizer-prices-are-here-to-stay
This report is produced via Chat GPT Plus Work, with review by Brian Arnall.
Sulfur Fertilizer in Wheat: Is It a Have-To?
Brian Arnall, Precision Nutrient Management Extension Specialist.
Sulfur has become a much bigger part of the fertility conversation over the last several years, and for good reason. We are producing higher-yielding crops, removing more nutrients from our fields, and receiving less sulfur from atmospheric deposition than we did several decades ago. But that does not mean sulfur fertilizer has become a “have-to” application for every wheat field.
Ms. Kelby Linn’s research provides a good example of why soil testing still matters. Across the environments in this study, sulfur fertilizer did not increase wheat grain yield. The soil was able to supply enough sulfur to meet the yield demand of the crop. When fertilizer margins are tight, that is important. Applying a nutrient that is already present in sufficient amounts is an expense without a yield return. At the same time, these results should not be interpreted to mean that sulfur fertilizer is unnecessary. Sulfur management is ultimately a mass-balance issue. Every bushel we harvest removes nutrients from the field. As yields increase, nutrient removal increases. If we continually remove more sulfur than the soil and other sources can supply, at some point we have to replace it.
That is why I am more concerned about sulfur in intensive, high-yield production systems, particularly on sandier soils and soils with lower organic matter. These soils generally have less capacity to supply sulfur, while a high-yielding crop is removing more of it. That combination increases the likelihood of sulfur becoming limiting. This is where soil testing becomes a valuable management tool. Rather than treating sulfur as something wheat either “always needs” or “never needs,” we should identify the fields where soil supply is unlikely to meet crop demand and put our fertilizer dollars there.
It is also important not to carry the wheat results presented here across every cropping system. Our ongoing work in corn has shown more response to sulfur fertilizer than we have observed in wheat. That fits the larger nutrient-removal discussion, particularly as we push corn yields higher. We will share two years of data after this year’s corn harvest.
Kelby’s research also raises another interesting question. If the soil already contains enough sulfur to maximize wheat grain yield, does additional sulfur do anything? His work suggests that it can. The response may not be additional bushels, but changes in how nitrogen is used and, ultimately, the quality and functionality of the grain.
Understanding Sulfur’s Role Beyond Grain Yield
Kelby Linn and Brian Arnall
Why Nitrogen and Sulfur Must Work Together
Nitrogen (N) has long been recognized as the most important nutrient for winter wheat production. It is a primary driver of vegetative growth, grain yield, and grain protein concentration, making N management the focus of most wheat fertility programs across Oklahoma. Sulfur (S) plays a different but complementary role. Nitrogen supplies the building blocks needed to produce proteins, while S is needed to form sulfur-containing amino acids such as cysteine and methionine. These amino acids contribute to the bonds that strengthen gluten proteins and influence dough strength, elasticity, and overall baking performance. When S becomes limiting, wheat may continue to take up N but may be less efficient at incorporating that N into functional storage proteins. Therefore, the relationship between N and S may become increasingly important as N rates and yield potential increase. The literature suggest that relationship can be wrong in both directions were N is in excess and S is deficient can cause yield loss but also where S is in excess and N is deficient we can experience loss.
Understanding the System
To better understand how S behaves under different N environments, field trials were conducted across north-central Oklahoma and south-central Kansas during the 2023–2025 growing seasons. The objective was to determine whether S responses differed when N was limiting compared with a high-N production environment.
Two N fertilizer rates were evaluated using ammonium sulfate (AMS) and urea:
- 60 lb N/ac, representing a sub-optimal or N-limited environment
- 140 lb N/ac, representing a high-N environment where S could have greater potential to become limiting
Each N rate was combined with five S rates supplied as AMS: 0, 5, 10, 20, and 30 lb S/ac.
Sulfur was applied before jointing, between Feekes 4 and 6, with the top-dresss N application, when wheat nutrient uptake is increasing and the crop is transitioning toward reproductive development. This allowed us to evaluate the influence of S on grain production, N utilization, and grain quality under both N-limited and high-N conditions.
Soil testing was an important part of interpreting the results. Across the locations, sulfate-S was present in the soil profile before fertilizer application. Soil test S varied among sites and depths, reinforcing that the amount of S already available to the crop can differ considerably among fields.
Table 1. Average composite soil sample results of pH, organic matter (OM), nitrate, and SO4 for all locations of the S interaction study.
First, What Happened to Yield?
Nitrogen remained the dominant factor controlling grain yield. Across environments, average wheat yield increased from 46 bu/ac with the lower N rate to 56 bu/ac with the higher N rate. Sulfur, however, did not significantly increase grain yield. Soil tests indicated that the sites generally contained measurable sulfate-S, which correctly predicted the lack of a yield response. If grain yield had been our only measurement, the story could have ended there. But the addition of S affected several characteristics related to how the grain performed during milling and dough development, particularly under the high-N treatment.
Why Wheat Quality Matters
Most Oklahoma wheat producers market wheat based primarily on grain yield and protein concentration. Once wheat moves farther through the grain chain, however, millers and commercial bakeries evaluate additional characteristics that determine how the flour performs. Hard red winter wheat is valued for its ability to produce strong bread flour. That ability depends not only on the amount of protein in the grain but also on the structure and functionality of those proteins. Nitrogen applications generally increases grain protein concentration, while S can influence the composition of those proteins. Adequate S promotes the formation of S-containing proteins involved in strong gluten networks. As a result, two wheat samples with similar protein concentrations can potentially behave differently during milling and baking.
Looking Beyond Grain Protein
Several measurements were used to evaluate wheat and flour quality. Grain protein represents the total protein concentration of the kernel and remains an important factor in wheat marketing. Flour protein measures the protein concentration after the bran and other components have been removed during milling. Other measurements tell us more about milling and baking performance. Milling yield describes how much usable flour can be produced from the grain, while flour ash is an indicator of the amount of mineral material remaining in the flour and can help evaluate milling efficiency. Falling number provides information about alpha-amylase activity and potential preharvest sprouting. Gluten index is particularly useful for evaluating gluten strength. A higher gluten index generally indicates stronger gluten that can better maintain dough structure during mixing and fermentation.
What Happened When We Made Dough?
One of the unique aspects of this study was evaluating flour with DoughLAB analysis. Rather than measuring only grain or flour composition, DoughLAB measures how flour behaves during mixing. Development time measures how long the dough must be mixed to reach optimum consistency. Dough stability measures how long the dough maintains that consistency before beginning to break down. Mixing tolerance index, or MTI, measures how rapidly the dough weakens after optimum development. Water absorption measures the amount of water required to produce dough at a standard consistency.
Of these measurements, dough stability provided one of the more interesting S responses. Under the high-N treatment, average dough stability increased from approximately 6 minutes without S to nearly 15 minutes at the highest S rate. Greater dough stability indicates that the gluten network was able to withstand mixing for a longer period before breaking down. For commercial baking, this can be important because stronger, more stable dough generally provides greater tolerance during mixing and more consistent performance during processing.
What Did We Learn?
Across these environments, N remained the primary factor controlling grain yield. Increasing N increased average yield, while adding S did not provide a significant yield response. However, the absence of a yield response did not mean S had no effect on the wheat. Under high-N conditions, S improved several measurements associated with grain and dough functionality, including gluten strength, dough development, and dough stability.
These results help separate two questions that are sometimes treated as the same question: Does the crop need S to produce more grain, and does S influence what happens inside the grain?
At the locations included in this study, the answer to the first question was no. The soils supplied enough S that additional fertilizer did not increase yield. The second question was more complicated. Sulfur influenced characteristics associated with protein functionality and end-use quality, particularly when N supply was high. That does not mean S should be applied routinely to improve wheat quality. For producers, the first fertilizer decision should still be based on whether the crop is likely to become S deficient. Soil testing, soil texture, organic matter, yield potential, and production history all provide information that can help make that decision. The larger lesson from this work is that S has a role in wheat beyond simply producing more bushels. Understanding that role helps us make better fertilizer decisions while continuing to put fertilizer where it is most likely to provide a return.
Data drawn from The Influence of Sulfur Under Nitrogen Extremes in Winter Wheat.
Linn, Kelby DeeAnn. Oklahoma State University ProQuest Dissertations & Theses, 2026. 32668685.
Cheap Nitrogen is not always the best Nitrogen, Timing matters
Brian Arnall: Precision Nutrient Management Extension Specialist, Oklahoma State University
In 2020, we published a summary of four OSU trial series comparing pre-plant nitrogen (N) to in-season N in grain-only winter wheat. https://osunpk.com/2020/09/10/value-of-in-season-application-for-grain-only-wheat-production/ Since then, three of those trial series have made it through peer review, and additional analyses have added considerably more data to the story. From both historic data from Dr. Raun’s program and new work. All together, these studies now represent more than 90 Oklahoma site-years across a wide range of environments, N rates, and application timings. So, after several more years of research, has the conclusion changed?
Does waiting to apply nitrogen cost wheat yield?
Across these studies, moving N from pre-plant to a properly timed in-season application generally maintained or increased grain yield. How often in-season N increased yield varied among datasets. Souza et al. found that winter wheat could recover from early N stress without sacrificing yield over a surprisingly wide application window. In other studies, in-season N was statistically similar to pre-plant N. The important point is that delaying N did not automatically mean giving up yield.
The Regional N study started by Dr. Raun 2in 2009, adds an important environmental piece to the story. Split N out yielded pre-plant N in approximately 29% of the 52 site-years, specifically those classified as highly responsive to N. These years tend to be wetter environments with greater yield potential. In the remaining 71%, split and pre-plant N produced statistically similar yields. Across all 52 site-years, splitting N never resulted in a significant yield loss compared with pre-plant N.
When a yield advantage with in-season N occurred, it could be meaningful. One study found a single in-season application produced approximately 8% greater yield than a full-rate pre-plant application. Sharry’s Gallagher/Green Hammer study found a single Feekes 4 (spring green up) application averaging approximately 11% greater yield than a single pre-plant application across two varieties and four site-years. The Regional N analysis found an approximately 5.4 bu/ac, or 14%, advantage for split N over pre-plant N in highly N-responsive environments, while there was no difference in the remaining environments. The message isn’t that in-season N always produces more wheat. It doesn’t. Properly timed in-season N generally maintained yield, and about 58% of the time increased it.
Protein Tells an Even More Consistent Story
Protein responded more consistently to N timing than yield. Later N increased grain protein across nearly every dataset. In the Regional N study, split N increased protein by 0.8 percentage points above the pre-plant compared with a 1.1-point increase from all N applied in-season. That advantage occurred across every environmental response category. In the end yield response to delayed N depends heavily on environment. The protein response is considerably more consistent.
If In-Season N Works, Is There a Reason to Split It?
Once the decision is made to move N away from a full pre-plant application, another question follows: should some N still go out pre-plant and the remainder in-season, or can the entire rate wait until the growing season? Two datasets tested that question directly, and neither found a consistent yield advantage to splitting N over a single, well-timed in-season application.
Sharry’s study found that a single green up application out-yielded both two-way and three-way splits by approximately 4.4 to 9.4 bu/ac at the site-years where treatments differed. At no site-year did a split application out-yield the single in-season timing. Abiola (2025) reached essentially the same conclusion. A single in-season application matched or exceeded a 50/50 pre-plant/in-season split across the timings evaluated. There was, however, an important exception. As the single in-season application was pushed into late March and April, having some N already applied reduced the potential downside.
Splitting N appears to be more about risk management than yield management.
Putting some N out early provides insurance against weather, field conditions, equipment problems, or other factors that prevent the planned in-season application from being made on time. If a single in-season application can be made at the proper time, however, these data provide little evidence that splitting N improves yield. So, in the end you reduce the “risk” but double application cost.
Timing Still Matters
None of this should be interpreted as saying N can be applied whenever it is convenient. The window for applying N to grain-only winter wheat is wider than many growers assume, but it isn’t unlimited. As application moves later, the opportunity for unfavorable weather to interfere with N availability becomes increasingly important.
The Regional N study provides a good example. For post top-dress applied N rainfall alone explained 27% of the site-to-site variation in how much the crop responded to N. The environments where split N increased yield over pre-plant N were generally the wetter, higher-yielding environments.
Waiting on N is a management strategy. Waiting too long is not.
Moving N in-season allows the rate decision to be made when considerably more is known about stand, growing conditions, and yield potential. But that flexibility only has value if the application is made while the crop can still effectively use the N. The data shows that the most risk adverse timing falls in the January to mid-March time frame.
What About Fertilizer Price?
Agronomy is only part of the decision. Anhydrous ammonia can provide a substantial cost-per-pound-of-N advantage over fertilizer sources typically used for in-season applications. When that price gap becomes large, the in-season strategy needs to create enough additional value through yield, protein, improved N-rate decisions, or reduced N loss to pay for the more expensive source.
The break-even calculation is straightforward: Additional N cost per acre ÷ wheat price = additional bushels needed to break even. At a 100 lb N/ac rate, every $0.10/lb difference in N price represents $10/ac in fertilizer cost.
For example, if the in-season N source costs $0.30/lb N more, that is a $30/ac disadvantage before the crop is planted. At $4.00 wheat, in-season N needs to produce 7.5 additional bu/ac to cover that difference. At $5.00 wheat, it needs 6 bu/ac, and at $6.00 wheat, it needs 5 bu/ac.
The range becomes fairly large as the difference in N price changes. At a 100 lb N/ac rate and wheat prices between $4 and $6/bu, a $0.20/lb N-price difference requires roughly 3 to 5 additional bu/ac, while a $0.50/lb difference requires roughly 8 to 13 additional bu/ac.
That doesn’t make either strategy automatically more profitable. In environments where yield is the same, the cheaper N source has the economic advantage. Where in-season N increases yield or protein, the economics can move in the other direction. There is also another economic benefit to waiting that is harder to put into a simple table: by waiting, the producer can adjust the N rate to the yield potential that is there rather than the yield potential hoped for before planting.
So fertilizer price adds another question to the N-timing decision: How much is the flexibility of waiting worth this year?
After more than 90 Oklahoma site-years, there is little evidence that grain-only winter wheat inherently benefits from having the entire N requirement available before planting. A properly timed in-season application generally maintains yield and can increase yield under responsive conditions. The opportunity to increase grain protein is even more consistent. Waiting also allows the final N decision to be made when the producer knows considerably more about the crop, weather, and realistic yield potential.
Splitting N does not appear to provide an additional yield benefit over a single, properly timed in-season application. Its primary value is insurance against missing that application window. But fertilizer price matters. When anhydrous or another pre-plant source provides N substantially cheaper than the available in-season source, those savings have real value and should be weighed against the potential benefits of waiting. There isn’t one N-timing strategy that wins every year. The goal isn’t simply to maximize yield or minimize fertilizer cost. It is to choose the N source, rate, and timing combination that provides the best economic return for the conditions in front of you.
These conclusions apply to grain-only winter wheat. Dual-purpose wheat requires sufficient fall growth for forage production and has a different early-season N requirement.
If you have any questions or comments, please feel free to reach out.
Brian Arnall
b.arnall@okstate.edu
Sources
Souza, J.L.B., Antonangelo, J.A., Silva, A.O., Reed, V., and Arnall, B. 2022. Recovery of Grain Yield and Protein with Fertilizer Application Post Nitrogen Stress in Winter Wheat (Triticum aestivum L.). Agronomy 12:2024.
Abiola, S.O., Souza, J.L.B., Sharry, R., Derrick, J.R., Maatougui, M., and Arnall, D.B. 2025. Split nitrogen applications provide no benefit over a single well timed application in rainfed winter wheat. Frontiers in Plant Science 16:1698494.
Ballagh, B., Ballagh, A., Bushong, J., and Arnall, D.B. The Effect of Nitrogen Fertilizer Placement and Timing on Winter Wheat Grain Yield and Protein Concentration.
Sharry, R. 2025. Response to nitrogen timing of varying winter wheat genotypes Dissertation, https://hdl.handle.net/20.500.14446/344867
Regional N study. 52 Oklahoma site-years, 2009–2023, Okstate Soil Fertility data unpublished.
OSUNPK Fertilizer Market Outlook — July 27, 2026
Produced by Chat GPT Work, reviewed by Brian Arnall, OSU Precision Nutrient Management.
Oklahoma fertilizer markets moved in two different directions during the latest reporting period. Nitrogen prices generally declined, while phosphate and potash remained nearly steady. That local stability does not mean the broader market is free of risk. International production costs, sulfur availability, trade flows and large import programs continue to influence the prices Oklahoma producers may encounter later in the season.
The USDA’s July 24 Oklahoma report placed urea at an average of $672.29 per ton, down $14.42 from the previous report. UAN 28 declined $16 to $472.60, UAN 32 fell $5 to $548.86, and anhydrous ammonia declined $29 to $947. One reported urea quote fell by approximately $300 per ton, while an NH₃ quote moved below $900 and a UAN 28 quote dropped below $400. Those individual movements contributed to unusually wide ranges and should not be treated as representative statewide prices without verification.
The USDA attributed part of the softer market to reduced fertilizer demand during triple-digit heat. Seasonal demand also appears less urgent following major spring and early-summer applications. However, the spread between low and high quotes remains substantial: $365 per ton for urea, $232 for UAN 28 and $225 for NH₃. Those differences make product basis, location and service charges particularly important when comparing offers. (USDA Oklahoma Production Cost Report)
International nitrogen conditions remain uncertain. Fertilizer-market analyst Josh Linville recently identified the resumption of vessel traffic through the Strait of Hormuz and the possibility of renewed Chinese urea exports as potentially bearish influences. Either development could improve global availability. However, fertilizer remains expensive relative to grain prices, and freight, energy or geopolitical disruptions could quickly change the cost calculation. (Josh Linville market commentary)
Oklahoma phosphate prices showed little immediate movement. DAP averaged $952.78, an increase of $2.22, while MAP held at $942.88. The local numbers appear quiet, but upstream phosphate conditions deserve attention. Linville has noted renewed strength in international phosphate values as limited sulfur availability and high production costs constrain output.
Sulfur matters because it is used to produce sulfuric acid, a critical input in manufacturing phosphoric acid and finished phosphate fertilizers such as DAP and MAP. Ammonia is another important production input. Consequently, higher sulfur or ammonia costs can support phosphate prices even when Oklahoma retail quotations have not yet responded. This is an upstream warning signal rather than a prediction that local prices must rise. (Josh Linville on phosphate and sulfur, World Bank fertilizer-market analysis)
Potash remained the quietest major nutrient in Oklahoma. The reported average increased only 75 cents to $491.55, with a range of $460 to $550. Global potash supply is geographically broader than the supply chain for several nitrogen and phosphate inputs. Expanded or recovering shipments from major producing regions may help moderate market pressure, although trade restrictions, transportation constraints and regional demand can still affect delivered costs.
International buying also remains important. India reported importing more than 3.2 million metric tons of urea and DAP during its first fiscal quarter and is pursuing longer-term overseas supply agreements. Large import programs can affect competition for available urea and phosphate cargoes, especially when export availability is already uncertain. (Times of India fertilizer-import report)
For Oklahoma producers, the current report offers a somewhat more favorable nitrogen signal, but not a uniform one. Wide quote ranges mean that comparison shopping may be as important as the regional average. Phosphate prices are locally stable, while sulfur availability and production costs remain meaningful external risks. Potash is comparatively steady.
Before acting on any quotation, confirm the nutrient analysis, cash-price basis, pickup or delivery terms, quote expiration and whether application or blending charges have been separated. UAN quotations should always be identified as either 28% or 32% before comparison.
Market Sources
How Much Nitrogen Does Double Crop Corn Need in Oklahoma?
Kelby Linn, MS Precision Nutrient Management
Emily Staton, MS Precision Nutrient Management
Josh Lofton, Cropping Systems Management
Brian Arnall, Precision Nutrient Management
Double crop (DC) corn is gaining attention in Oklahoma as producers look for opportunities to increase productivity following wheat harvest. While DC soybeans and sorghum remain common options, corn can serve as an alternative when planting windows are missed or when producers want to diversify their rotation. In Oklahoma systems, it is suggested DC corn is followed by a full season soybean crop the next year. This allows producers to maintain an intensive cropping system while maximizing land use. However, managing fertility in DC corn can be challenging because the crop is grown under a different environment than full season corn. One of the questions producers ask is how much nitrogen (N) is needed to maximize returns. Nitrogen is typically the largest fertilizer expense in corn production, but applying more N does not always result in higher yields. Recent Oklahoma research suggests DC corn may require less N than many would expect.
Understanding the System
To evaluate N requirements under Oklahoma DC conditions, field trials were conducted across 11 site years during the 2024 and 2025 growing seasons (Table 1). Corn was planted directly into wheat residue following harvest, creating a true DC production system. Nitrogen was applied as urea (46-0-0) at 13 rates ranging from 0 to 180 lbs N/acre in 15 lb N increments. The following data was collected: biomass production, grain yield, and grain quality responses across environments. The goal was to identify how much N is needed to maximize yield and profitability in Oklahoma DC corn.
Table 1. Field study locations for the 2024 and 2025 double crop corn trials in Oklahoma. Each location is listed with respective planting dates, corn varieties, planting populations and harvest date.
| Location | Planting | Variety | Population | Harvest |
| Perkins | 6/28/2024 | DK119-30 | 20k | 11/9/2024 |
| 7/11/2025 | DKC117-27RIB | 20k | 11/14/2025 | |
| Stillwater | 6/30/2024 | DK119-30 | 20k | 11/11/2024 |
| 7/12/2025 | DKC117-27RIB | 20k | 11/13/2025 | |
| Perry | 6/28/2024 | DK119-30 | 20k | 11/16/2024 |
| 7/7/2025 | DKC117-27RIB | 20k | 11/12/2025 | |
| Perry (Irrigated) | 7/7/2025 | DKC117-27RIB | 28K | 11/12/2025 |
| Lahoma | 7/9/2025 | DKC117-27RIB | 20k | 11/18/2025 |
| Fort Cobb (Irrigated) | 7/2/2025 | DKC117-27RIB | 28K | 11/15/2025 |
Yield Response: Nitrogen Helped, But Only to a Point
Across all harvested site years, N applications significantly influenced grain yield when environment was not the limiting factor. Average yields ranged from 40 to 94 bu/ac, demonstrating how variable DC corn performance can be from year to year and field to field (Staton, 2026) (Figure 1). While some locations responded positively to N fertilizer, others showed little response even when rates reached 180 lbs N/ac. The consistent finding was yield responses often plateaued around 60 lbs N/ac. Once this point was reached, additional fertilizer rarely produced enough additional grain to justify the added cost. Across two Oklahoma studies representing 11 site-years, unfertilized double-crop corn averaged approximately 52 bu/ac. That finding highlights just how much nitrogen can be supplied by the soil through residual nitrate and mineralization before fertilizer is applied. These results suggesting existing soil N and nutrient mineralization contributed significantly to crop demand (Staton, 2026).
Figure 1. Increase in yield of the highest yielding treatment as compared to the non-fertilized check yields of each location. Adapted from Staton (2026)
The Real Story: Return on Investment
While producers naturally focus on maximizing yield, these fertilizer decisions should be based on profitability. Average economic return peaked near 60 lb N/ac. Beyond that rate, additional fertilizer consistently reduced profit (Figure 2). Although individual economic returns varied among environments, the agronomic data suggest producers should approach DC corn fertility programs with realistic yield expectations. Unlike high yielding full season corn, DC systems often encounter environmental limitations that reduce the return on additional fertilizer investment.
Figure 2. Average profit response to nitrogen rate in US dollars (USD)/ac. Adapted from Staton (2026).
What This Means for Oklahoma Producers
The results from this study closely align with previous Oklahoma research evaluating N response in DC corn. Wyma (2022) reported approximately one additional bushel of grain for every 1.8 lbs N applied above the unfertilized control, similar to Staton (2026) who observed one additional bushel for every 1.7 lbs N in responsive environments. Together these studies suggest Oklahoma DC corn requires approximately 1.75 lbs N for every additional bushel of expected yield above 50 bu ac-1.
The goal of nitrogen management is not to apply the most fertilizer, it is to apply the right amount. Two independent Oklahoma studies now indicate that double-crop corn often requires substantially less N than full-season corn. Matching N rates to realistic yield potential can improve profitability while reducing unnecessary fertilizer costs.
Take Home
- Double crop corn is a economically viable option in Oklahoma.
- Use lower total N rates than full-season corn.
- Across two independent studies’, the unfertilized corn averaged about 50 bushels per acre.
- 1.75 lb N per expected additional bushel above the unfertilized expectation.
- Base final N rates on realistic yield potential and expected moisture.
- Consider residual soil nitrate following wheat before increasing fertilizer rates.
- Avoid applying N beyond expected crop demand.
References
Alcoz, Mercedes M., Frank M. Hons, and Vincent A. Haby. 1993. “Nitrogen Fertilization Timing Effect on Wheat Production, Nitrogen Uptake Efficiency, and Residual Soil Nitrogen.” Agronomy Journal 85(6):1198–1203. doi:10.2134/agronj1993.00021962008500060020x.
Chang, Jen-Hu. 1981. “Corn Yield in Relation to Photoperiod, Night Temperature, and Solar Radiation.” Agricultural Meteorology 24:253–62. doi:10.1016/0002-1571(81)90049-2.
Kravchenko, Anatoliy G., and Kurt D. Thelen. 2007. “Effect of Winter Wheat Crop Residue on No-Till Corn Growth and Development.” Agronomy Journal 99(2):549–55. doi:10.2134/agronj2006.0192.
Liu, Zheng, Jia Gao, Fei Gao, Shuting Dong, Peng Liu, Bin Zhao, and Jiwang Zhang. 2018. “Integrated Agronomic Practices Management Improve Yield and Nitrogen Balance in Double Cropping of Winter Wheat-Summer Maize.” Field Crops Research 221:196–206. doi:10.1016/j.fcr.2018.03.001.
Staton, Emily. 2026. “Nitrogen Management in Double Crop Corn” M.S., Oklahoma State University, United States — Oklahoma.
Wyma, Rhiannon Nichole. 2022. “Corn Grain Yield Response to Nitrogen Rate and Plant Population in Full and Double-Crop Systems.” M.S., Oklahoma State University, United States — Oklahoma.
Bigger Isn’t Always Better: The Relationship Between Plant Size, Yield Potential, and Yield Stability in Summer Crops
Josh Lofton, Cropping Systems Specialist
In the last several years, warmer springs and higher/widespread rainfall have resulted in summer crops reaching with a high amount of vegetative growth. This season has been quite different for the most part, cooler temperatures and more sporadic rainfall has resulted in much smaller plants. So that begs the question, are larger or smaller plants better for yield in Oklahoma. While many that have spent time in Oklahoma will probably have a preference, there is no direct answer to this question.
Larger plants generally have more leaves, more stems, more branches, and more overall biomass. They often appear healthier and more productive throughout the growing season.
In higher rainfall and lower stress environments, this assumption is true. Greater vegetative growth can support higher yield potential because larger plants capture more sunlight, accumulate more photosynthates, and develop a greater capacity to support grain or seed production.
However, in Oklahoma and throughout the Southern Great Plains, yield potential and yield stability are not always the same thing.
The challenge facing producers across this region is that crops must balance the opportunity to maximize yield with the risk of running short on water during critical reproductive growth stages. As a result, the plant with the greatest theoretical yield potential is not always the plant that produces the most grain across a range of environmental conditions.
The Tradeoff Between Yield Potential and Yield Stability
Many may have heard of this difference. Even you if have not directly of these concepts, most in Oklahoma will be familiar with the trade-offs
Yield potential refers to the maximum yield a crop can achieve when environmental conditions are favorable, and resources are not limiting.
Yield stability refers to a crop’s ability to maintain performance across varying environmental conditions, including drought, heat stress, and erratic rainfall.
These two characteristics are often related, but they are not always aligned.
High vegetative growth frequently possesses greater yield potential because they can intercept more sunlight and support more reproductive structures. However, those same plants often require greater amounts of water throughout the season.
In contrast, plants with more moderate growth habits may have slightly lower maximum yield potential, but they often maintain more consistent performance when environmental stresses occur.
So the difference between excessive, adequate, and too low vegetative production is not consistent and is impacted by a part of the year not yet experienced.
For producers in the Southern Great Plains, where growing conditions can change dramatically from one season to the next, yield stability can be just as important as maximum yield potential.
Why More Growth Often Means More Yield Potential
The relationship between vegetative growth and yield begins with photosynthesis.
More leaves generally mean:
- Greater sunlight interception
- Greater photosynthetic capacity
- More carbohydrate production
- More potential reproductive sites
And when we are talking about farming, what we are often farming is the sunlight indirectly through the crops we are growing. Therefore, the higher amount of sunlight that can be captured, this higher potential yield can be.
In soybean, larger plants often produce more nodes and branches, creating additional locations for pod formation.
In grain sorghum, larger canopies can support greater grain production when moisture remains adequate through grain fill.
In corn, larger plants often contribute to greater kernel production and kernel weight under favorable conditions.
Because of these relationships, management practices that encourage vigorous growth are frequently associated with high yield environments.
The key phrase, however, is under favorable conditions.
The Hidden Cost of Large Plants
Every leaf that captures sunlight also loses water.
As plant size increases, so does transpiration demand. Larger plants require more water simply to maintain normal physiological activity.
This creates a challenge in many Oklahoma production environments.
Rainfall is often adequate during early vegetative development, allowing crops to establish large canopies and accumulate substantial biomass (often during the months of April and early May). However, the period from flowering through grain fill frequently coincides with:
- Higher temperatures
- Greater evaporative demand
- Less reliable rainfall
- Increasing soil moisture depletion
This can be a two-fold issue. One, higher vegetative production early could have utilized and drained total surface and subsurface moisture, which is now not available during reproductive growth. However, it also increased daily moisture demand. This can result in with similar soil moisture and rainfall, a smaller plant will have a lower moisture demand than a larger plant.
The consequence is often a reduction in grain or seed production precisely when yield is being determined.
Soybean: A Classic Example
Soybean perhaps provides the best illustration of this concept.
When moisture is abundant, larger soybean plants can be extremely productive. Additional nodes and branches create opportunities for greater pod production, and large canopies intercept significant amounts of sunlight.
However, soybean also possesses one of the longest reproductive periods among major summer crops.
A soybean crop must successfully retain flowers, maintain pods, and fill seeds over an extended period. Water stress at any point during this process can reduce yield.
Large soybean plants often consume considerable amounts of water during vegetative growth. If drought develops during pod set or seed fill, those plants may experience:
- Increased flower abortion
- Increased pod abortion
- Reduced seed size
- Premature canopy senescence
In contrast, a more moderate-sized soybean plant may use less water during early development and preserve soil moisture for reproductive growth.
While that plant may possess fewer nodes or branches and therefore slightly lower maximum yield potential, it may be better positioned to maintain yield under stressful conditions.
Seeing this in practice
As shown in Figure 1, plant growth regulation substantially reduced soybean height compared to untreated plants. Three weeks after treatment implementation, regulated plants ranged from 5–10 inches shorter than untreated plants. These reductions in height were accompanied by fewer mainstem nodes, but plants compensated by producing more branch nodes and increasing canopy coverage. The response was relatively consistent across both growing seasons, demonstrating that soybean plants can modify their growth habit when mainstem development is restricted.
Figure 1. Impact of plant growth regulation (physical removal) on soybean plant height compared to untreated plants. Data were collected across the 2022 and 2023 growing seasons.
While reduced plant size altered canopy architecture, the impact on yield differed substantially between years (Figure 2). In 2022, when environmental conditions were generally favorable and resources were less limiting, plant growth regulation did not improve yield. In fact, yields were slightly lower than the untreated control. This response likely reflects the reduced yield potential associated with smaller plants, as larger soybean canopies often intercept more light, accumulate greater biomass, and support higher seed production when adequate moisture is available throughout the season.
However, the response was markedly different during 2023, when moisture became increasingly limiting later in the growing season. Under these conditions, regulated plants significantly outyielded the untreated plants. The smaller canopy likely reduced seasonal water use and delayed soil moisture depletion, leaving more water available during critical reproductive growth stages. In contrast, larger untreated plants developed greater vegetative biomass and therefore higher water demand earlier in the season. Although these larger plants possessed greater theoretical yield potential, they were more susceptible to late-season drought stress when water availability became limited.
These results illustrate an important principle for summer crop production systems in water-limited environments. Larger plants often possess higher yield ceilings because of their greater vegetative growth and capacity to capture resources. However, that same vegetative growth can increase transpiration demand and accelerate soil water depletion, increasing the risk of yield loss if drought develops later in the season. Smaller plants may not achieve the same maximum yield potential in favorable years, but they often provide greater yield stability by reducing water demand and preserving resources for reproductive development. Consequently, the optimal plant size is often a balance between maximizing yield potential and minimizing drought risk, particularly in environments such as Oklahoma where late-season moisture stress is common.
Figure 2. Impact of plant height regulation on soybean yield during the 2022 and 2023 growing seasons. Yield responses differed between years, highlighting the tradeoff between maximum yield potential and yield stability under water-limited conditions.
Lessons from Grain Sorghum
Grain sorghum offers another excellent example.
One reason sorghum has traditionally been viewed as a drought-adapted crop is its ability to regulate water use throughout the season. Traits such as leaf rolling, reduced transpiration, and stay-green characteristics help preserve plant function during grain fill.
Many of these mechanisms do not necessarily maximize growth early in the season. Instead, they improve the likelihood that the crop can complete grain development under stressful conditions.
This strategy may occasionally sacrifice maximum yield potential in highly favorable years, but it often improves yield stability across multiple growing seasons.
Managing for Consistency Versus Chasing Maximum Yield
One of the most important questions growers must answer is whether they are managing for maximum yield potential or maximum yield consistency.
In highly productive environments with irrigation or reliable rainfall, encouraging aggressive vegetative growth may be appropriate because water limitations are less likely to restrict grain fill.
In contrast, dryland production systems throughout much of Oklahoma often reward a more balanced approach.
The goal is not necessarily to produce the largest crop canopy possible. Rather, it is to produce enough canopy to efficiently intercept sunlight while preserving sufficient water to support reproductive growth later in the season.
Bigger Isn’t Always Better—Especially in Dryland Systems
This does not mean smaller plants are inherently superior.
A very small plant may lack sufficient leaf area to fully utilize available sunlight and may never achieve high yield potential regardless of rainfall conditions.
The ideal crop is rarely the smallest or the largest plant in the field.
Instead, the most successful crops are often those that achieve a balance between vegetative growth and resource conservation.
They develop enough biomass to support high levels of photosynthesis while avoiding excessive water consumption before reproduction begins.
Final Thoughts
Across Oklahoma and the Southern Great Plains, crop production is often a matter of managing risk as much as maximizing yield.
Larger plants frequently possess greater yield potential because they capture more sunlight and produce more biomass. However, that potential comes with increased water demand. When rainfall becomes limiting during flowering, grain fill, pod set, or seed development, those larger plants can become more vulnerable to stress.
Smaller or more moderately sized plants may not always produce the highest yields in ideal environments. However, they often provide greater yield stability because they conserve resources and maintain reproductive growth when environmental conditions deteriorate.
For soybean in particular, this tradeoff is frequently observed. The largest plants in July are not always the highest-yielding plants in October. More often, the most successful plants are those that balance growth with resource conservation, preserving enough water to support reproduction when it matters most.
In the Southern Great Plains, where late-season drought remains one of the greatest limitations to crop production, understanding the difference between yield potential and yield stability may be just as important as understanding yield itself.
Banding P for Acidic Soils: Its not the time to be paying for poor practice.
I am bringing this topic back to the surface now with the current outlook on phosphorus fertilizer. If you have heard its not only becoming more expensive but the supply is short and will likely stay short through summer into the fall, which wont help prices. So this year’s wheat crop, we need to be prepared to be smart with Phosphorus, and applying an extra 30lbs to band aid for soil acidity should not be in the cards. Look at it this way, if the phosphorus was at $0.66 a lb that $20 that could be spent on a ton of lime. That lime will last 3-5 years, while that P needs to be added every year. Not only that, but the lime will help root growth (better when we dry up), produce significantly more biomass, and make the phosphorus you’ve applied in the past available again for plant uptake. So make the plans now to soil sample as soon as this crop is off, you can get a soil test recommendation and plan for the lime trucks. This is also not the year to just apply phosphorus for the sake of applying. Soil tests are inexpensive relative to buying excess fertilizer.
Current quotes on 4.24.26 are at $0.54 + per lbs P2O5 with DAP at $830 a ton.
Quick Fertilizer Price Calculation:
Urea at $860 a ton means N is $0.93 a lbs.
DAP at $830 has $334 worth of $0.93 nitrogen and $495 of phosphorus at $0.54 a lb.
Banding P as a band-aid for soil acidity, not so cheap now.
Original Blog Posted in 2021
Whoi Cho, PhD student Ag Economics advised by Dr. Wade Brorsen
Raedan Sharry, PhD Student Soil Science advised by Dr. Brian Arnall
Brian Arnall, Precision Nutrient Management Extension.
In 2014 I wrote the blog Banding P as a Band-Aid for low-pH soils. Banding phosphate to alleviate soil acidity has been a long practiced approach in the southern Great Plains. The blog that follows is a summary of a recent publication that re-evaluated this practices economic viability.
Many Oklahoma wheat fields are impacted by soil acidity and the associated aluminum (Al) toxicity that comes with the low soil pH. The increased availability of the toxic AL3+ leads to reduced grain and forage yields by impacting the ability of the plant to reach important nutrients and moisture by inhibiting root growth. Aluminum can also tie up phosphorus in the soil, further intensifying the negative effects of soil acidity. More on the causes and implication of soil acidity can be found in factsheet PSS-2239 or here (https://extension.okstate.edu/fact-sheets/cause-and-effects-of-soil-acidity.html). The acidification of many of Oklahoma’s fields has left producers with important choices on how to best manage their fields to maximize profit.
Two specific management strategies are widely utilized in Oklahoma to counter the negative impacts of soil acidification: Lime application and banding phosphorus (P) fertilizer with seed. While banding P with seed ties up Al allowing the crop to grow, this effect is only temporary, and application will be required every year. The effects of liming are longer lasting and corrects soil acidity instead of just relieving Al toxicity. Historically banding P has been a popular alternative to liming largely due to the much lower initial cost of application. However, as P fertilizers continue to increase in cost the choice between banding P and liming needed to be reconsidered.
A recent study by Cho et al.,2020 compared the profitability of liming versus banding P in a continuous wheat system considering the impacts that lime cost, wheat price and yield goal has on the comparison. This work compared the net present value (NPV) of lime and banded P. The study considered yield goal level (40 and 60 bu/ac) as well as the price of P2O5 fertilizer and Ag Lime. The price of P2O5 used in this study was $0.43 lb-1 while lime price was dictated by distance from quarry, close to quarry being approximately $43 ton-1 and far being $81 ton-1. For all intents and purposes these lime values are equivalent to total lime cost including application. Wheat prices utilized in the study were $5.10 bu-1 and $7.91 bu-1. It is important to note that baseline yield level was not considered sustainable under banded P management in this analysis. This resulted in a decrease in yield of approximately 3.2 bu ac-1 per year. This is attributable to the expected continued decline in pH when banding P is the management technique of choice.
The analysis in this work showed that lime application is cost prohibitive in the short term (1 year) when compared with banding P regardless of lime cost, yield goal level, and wheat value (within the scope of this study). This same result can be seen over a two-year span when yield is at the lower level (40 bu ac-1). While in the short-term banding P was shown to be a viable alternative to liming, as producers are able to control ground longer lime application becomes the more appealing option, especially when producers can plan for more than 3 years of future production. In fact, under no set of circumstances did banding P provide greater economic return than liming regardless of crop value, yield, or liming cost when more than 3 years of production were considered and only under one scenario did banded P provide a higher NPV in a 3-year planning horizon.
While historically banding P was a profitable alternative to lime application for many wheat producers the situation has likely drastically changed. At the time of writing this blog (09/17/2021) Diammonium Phosphate (DAP) at the Two Rivers Cooperative was priced at $0.78 lb-1. of P2O5. This is a drastic increase in P cost over the last year or so since Cho et al. was published in 2020. With P fertilizer prices remaining high it will be important for producers to continue to consider the value of liming compared to banded P. This is particularly crucial for those producers who can make plans over a longer time frame, especially those more than 3 years.
Addendum: As fertilizer prices have continued to rise a quick analysis utilizing the $0.78 lb-1 of P2O5was completed to consider the higher P fertilizer cost. Under this analysis an estimated decrease in NPV of approximately $38 an acre for P banding occurred. When considering this change in NPV, lime application becomes the more profitable option for alleviation of soil acidity symptoms even in the short term (assuming lime price values are equivalent to the previous analysis). This underlines the fact that it is imperative to consider the impact on profitability of the liming vs. banding P decision in the current economic climate for agricultural inputs.
Link to the Open Access Peer Reviewed publication “Banding of phosphorus as an alternative to lime for wheat in acid soil” https://doi.org/10.1002/agg2.20071
Corn Hybrids’ Yield Response to Limited Well Capacities in the Central High Plains
Macie McPeak: M.S in Irrigation and Water Management
Sumit Sharma : Extension Specialist for High Plains Irrigation and Water Management
Background
The Central High Plains, which include the Oklahoma Panhandle, Southwest Kansas, Southeast Colorado, and Northern Texas Panhandle, is a heavily farmed semi-arid region that depends on the Ogallala Aquifer for irrigation to ensure stable crop yields. However, the continuous decline of the Ogallala Aquifer has resulted in increased need for irrigation strategies that conserve water while maintaining crop profitability. Corn remains the most water consuming crop with highest productivity per unit of irrigation applied, and strong economic returns in the Central High Plains region. However, corn is also the most sensitive to water stress among all the existing cropping systems (including sorghum, cotton, and sunflower, soybeans and wheat). Declining water table has reduced the well capacities in many areas in the region, which cannot meet crop water demand, making it a growing challenge for corn production. Therefore, there is a need for research in irrigation strategies and agronomic choices such as drought tolerant hybrids, seeding rate, planting date, and hybrid maturity for sustainable and profitable corn production with reduced well capacities in the region. This blog discusses the yield response of different corn hybrids to limited well capacities in the Oklahoma Panhandle area of the Central High Plains.
Limited well capacities only meet partial crop water demand, which in general leads to yield declines especially in high water demanding crops such as corn. Several previous studies suggest that crop productivity does not significantly decrease as long as irrigation is maintained at approximately 75–80% of full evapotranspiration (ET) replacement (Su et al., 2022; Klocke et al., 2007; Zhao et al., 2019). However, when irrigation levels are more restricted, such as under reduced well capacities, there can be substantial yield losses and diminished economic returns. The magnitude of yield reduction varies with region, hybrids, and growth stage at which water stress occurred. For example, in the Central High Plains the corn ET demand is highest in Texas Panhandle and decreases as we move north towards Nebraska. Zhao et al. (2019) found that applying 75% ET in the Texas Panhandle produced corn yields equivalent to full irrigation, whereas reducing irrigation to 50% caused significant yield reductions. Similarly, Klocke et al. (2007) reported that limited irrigation at roughly 50% of full ET replacement in Nebraska achieved 80–90% of fully irrigated yields across multiple crop rotations. Therefore, the irrigation strategies which work in one region may not work the same way in other regions with different crop water demand and must be tested for the region-specific climatic conditions.
The current study was conducted in 2025 at the Oklahoma Panhandle Research and Extension Center in Goodwell, OK. Four Pioneer brand corn hybrids including P13777 (113 day maturity), P10625 (110 day maturity), P05810 (105 day maturity), and P14346 (114 days maturity) were planted at 22,000 and 28,000 seeds per acre. The hybrids were irrigated with a center pivot fitted with variable rate irrigation system at 200, 300, 400, and 500 GPM well capacities. The well capacities were simulated by adjusting the frequency of irrigation events.
Results & Discussion
The crop received 12.1 inches of rain from planting until physiological maturity, while total rainfall from April till September was over 15 inches. Manual probing of the field showed near 4 feet soil profile at the time of planting which can hold up to 2 inches of plant available water per foot. The well capacities 200, 300, 400, and 500 GPM treatments received 7.4, 8.9, 10.8, and 12.0 inches of irrigation, respectively. The data showed no significant effect of population on corn yield across hybrids for any well capacity. However, the hybrids showed significant interaction with well capacities, which indicated that hybrid yield response varied at different capacities (Figure 1). In general, the average yield declined from longest maturity to shortest maturity hybrids irrespective of the well capacity, but was only statistically significant at for 200 GPM (Figure1). At this irrigation level, the shortest maturity hybrid P05081 yielded significantly lower yield than longest maturity hybrid P14364, while P13777 and P10625 were not different from either of these two hybrids.
Although there was no statistical difference among the hybrids at 500, 400, and 300 GPM, when compared across well capacities, yield reductions were most pronounced at the 200 and 300 GPM irrigation levels for each individual hybrid, indicating that irrigation capacity was the primary yield limiting factor under restricted water availability (Figure 2). While the exact causes of this abrupt decline are not yet understood, as mentioned in the beginning of this blog, previous literature has suggested that severe yield decline in corn can be expected when irrigation is reduced to 60% ET replacement in the study region. Both 300 and 200 GPM well capacities met 60 and 65% crop ET demand, while 400 and 500 GPM met 71 and75% crop ET demand, respectively. More data will be needed to ascertain these threshold levels of well capacities for corn production in this region.
All the hybrids showed a positive yield response to Irrigation+Rain with different yield gains per inch of water applied (Figure 3). Hybrid P10625 registered highest yield gain of 14.1 bushel per inch of water applied, followed by P13777 (12.0 bu), P05081 (11.9 bu), and P14364 (11.6 bu). The stronger coefficient of regression (>80%) for two short maturity varieties indicated that irrigation was stronger yield limitation factor for these hybrids, in comparison to 114 and 113-day maturity hybrids for irrigation explained on 67 and 69% variability, respectively. This suggests that besides irrigation there might be other factors which could contribute to filling the yield gaps for given irrigation levels in longer maturity hybrids.
Planting population did not significantly affect grain yield across irrigation capacities. When pooled across the hybrids for individual planting populations, 28,000 seeding rates resulted in gain of 0.1, 2.6, 5, and 12 bushels per acre for 200, 300, 400, and 500 GPM, respectively. This indicates that higher planting populations at well capacities of 400 or above should be considered, while reducing population at 300 GPM or lower might be more cost-effective option.
Take Home
- Irrigation capacity remains the primary determinant of yield potential under limited well capacities in the Central High Plains.
- Pre-irrigation and recharging the soil profiles will be critical to support crop water demand for limited well capacities.
- Short maturity hybrids appeared to have consistently lower average yield and more vulnerable for yield losses at limited irrigation. However, one must consider that the growing conditions were more conducive for corn production in 2025 which generally favor long maturity hybrids. Therefore, long-term data will be required to assess the performance of short maturity hybrids during inclement growing seasons.
- Even though population didn’t significantly influence the grain yield. The 28,000 seeding rates overall had higher average yield at 400 and 500 GPM. Therefore, producers should consider the higher population at these well capacities or more.
- Overall, irrigation is the most important factor for yields, but there is a need for long-term agronomic data on hybrid maturity and population along with economic analysis to ascertain these findings.
PRE-EMERGENT RESIDUAL HERBICIDE ACTIVITY ON SOYBEANS, 2025
Liberty Galvin, Weed Science Specialist
Karina Beneton, Weed Science Graduate Student.
Objective
Determine the duration of residual weed control in soybean systems following the application of Preemergent (PRE) herbicides when applied alone and in tank-mix combination.
Why we are doing the research
PRE herbicides offer an effective means of suppressing early-season weed emergence, thereby minimizing competition during the critical early growth stage. However, evolving herbicide resistance and the need for longer-lasting weed suppression underscore the importance of evaluating multiple modes of action and their residual properties alone and tank-mixed.
Field application experimental design and methods
Field experiments were conducted in 2022, 2023, and 2024 growing seasons in Bixby, Lane, and Ft. Cobb FRSU Research Stations across Oklahoma. Each herbicide (listed in Table 1) was tested individually, in 2-way combinations, 3-way mixtures, and finally as 4-way combinations that included all active ingredients listed at the label rate.
Soybeans were planted at rates between 116,000 and 139,000 seeds/acre from late May to early June, depending on the year and location. The variety used belongs to the indeterminate mid- maturity group IV, with traits conferring tolerance to glyphosate (group 9 mode of action), glufosinate (group 10), and dicamba (group 4). Not all soybean varieties have metribuzin tolerance. Please read the herbicide label and consult your seed dealer for acquiring tolerant varieties. Row spacing was 76 cm at Bixby and Lane, and 91 cm at Fort Cobb. PRE treatments were applied immediately after planting at each experimental location.
POST applications consisted of a tank-mix of dicamba (XtendiMax VG® – 22 floz/acre), glyphosate (Roundup PowerMax 3®- 30 floz/acre), S-metolachlor (Dual II Magnum® – 16 floz/acre), and potassium carbonate (Sentris® – 18 floz/acre). Applications were made on different dates, mostly after the first 3 weeks following PRE treatments. These timings were based on visual weed control ratings, particularly for herbicides applied alone or in 2-way combinations, which showed less than 80% control at those early evaluation dates. The need for POST applications also depended on the species present at each site, with most fields being dominated by pigweed, as illustrated in the figure below.
Results
Tank-mixed PRE herbicide combinations generally provided superior residual control compared to a single mode of action application (Shown in Figure 1). Timely post-emergent (POST) herbicide applications helped sustain high levels of weed suppression, particularly as the effectiveness of residual PRE declined.
Residual control of tank-mixed PRE
Some herbicides applied alone or in simple 2-way mixes, such as sulfentrazone + chloransulam- methyl and pyroxasulfone + chloransulam-methyl required POST applications within 20 to 29 days after PRE, indicating moderate residual control.
In contrast, 2-way combinations containing metribuzin, such as sulfentrazone + metribuzin and pyroxasulfone + metribuzin, extended control up to 50 days after PRE in some cases, highlighting metribuzin’s importance even in less complex formulations.
Furthermore, 3-way and 4-way combinations including metribuzin provided the longest-lasting control, delaying POST applications up to 51–55 days after PRE.
Injury of specific weeds
Palmer amaranth (Amaranthus palmeri) control in Bixby was consistently high (≥90%) at 2 weeks after PRE in 2022 and 2024 across all treatments. At 4 WAPRE, treatments containing metribuzin alone or in combination maintained strong control (90% or greater).
Texas millet (i.e., panicum; Urochloa texana) and large crabgrass (Digitaria sanguinalis) were effectively managed with most treatments delivering over 90% control early in the season and maintaining performance throughout. In 2024, control remained generally effective, though pyroxasulfone alone showed a temporary lack of control for Texas millet, and single applications declined in effectiveness against large crabgrass later in the season. These reductions were likely due to continuous emergence and the natural decline in residual herbicide activity due to weather. The most consistent late-season control for both species came from 3- and 4-way herbicide combinations.
Morningglory (Ipomoea purpurea) control reached full effectiveness (100%) only when POST herbicides were applied, across all years and locations. Their late emergence beyond the residual window of PRE herbicides reinforces the importance of sequential herbicide applications for season-long control.
Take home messages:
- Incorporating PRE and POST herbicides slows the rate of herbicide resistance
- Tank mixing with *different modes of action* ensures greater weed control by having activity on multiple metabolic pathways within the plant.
- Tank mixing with PRE herbicides could reduce the number of POST applications required, and
- Provides POST application flexibility due to residual of PRE application
For additional information, please contact Liberty Galvin at 405-334-7676 | LBGALVIN@OKSTATE.EDU or your Area Agronomist extension specialist.
Down and Dirty with NPK 