Home » Wheat
Category Archives: Wheat
The Mechanics of Soil Fertility: Use of Sugar in Field Crops
Jolee Derrick, Precision Nutrient Management Ph. D. Student
Grace Williams, Soil Microbiology Ph. D. Candidate
Brian Arnall, Precision Nutrient Management Specialist
Recently, there has been increased interest in adding sugar to spray tank mixes, whether for post-emergence weed control or foliar nutrient applications. While there is limited work on impact of sugar inclusion in herbicide applications, some papers have posed potential enhancement (Devine and Hall, 1990). But since this is coming from a soil science group, we will only focus on soil impact. Following up the last blog, unlike humic substances, which represent more complex and relatively stable carbon forms, sugar is a highly labile carbon source. This rapid utilization of simple carbon sources is well documented to stimulate microbial activity and growth (Kuzyakov and Blagodatskaya, 2015). The general idea of utilizing sugar applications is that sugar has the capacity to improve spray performance, stimulate biological activity, increase organic matter mineralization, and ultimately result in improved yields.
Sugar additions can influence soil processes differently depending on system conditions. In systems with higher residual nitrogen and organic matter, responses may differ from those observed in Oklahoma production environments, where soils are typically lower in organic matter and microbial activity can occur for much of the year. Understanding how sugar functions in these systems requires a basic discussion of carbon dynamics. Sugar itself is almost entirely carbon and is readily consumed by microbes. It’s a simple molecule, which allows it to dissolve easily in water and be quickly utilized in the soil system. Crop residues, like wheat straw, are also carbon-rich but much more complex. They contain cellulose, hemicellulose, and lignin which are long carbon chains that take time to break down because microbes need specialized enzymes to access them.
For the sake of simplicity, we can group carbon into two key pools: labile carbon and particulate organic matter (POM). Labile carbon includes easily decomposed materials, which include the previously mentioned simple sugars that microbes can metabolize rapidly. These pools differ in turnover time and microbial accessibility, with labile carbon driving short-term microbial responses (Cotrufo et al. 2013). POM breaks down more slowly and serves as a longer-term nitrogen source through residue breakdown.
Soil microorganisms require both carbon and nitrogen to grow and maintain biomass, typically at a ratio of approximately 24 parts carbon to 1 part nitrogen. When readily available carbon is abundant, but nitrogen is limited, microbes increase their nitrogen demand and begin scavenging nitrogen from the surrounding soil. This process, better known as nitrogen immobilization, temporarily reduces nitrogen availability to crops. Additions of readily available carbon sources have consistently been shown to increase microbial nitrogen immobilization in soil systems (Recous et al. 1990).
In systems where sufficient nitrogen is present, microbial populations can expand rapidly. Fast-growing microbial species may dominate, continuing to immobilize nitrogen within their biomass. Eventually, when nitrogen becomes limiting, microbial populations decline to levels the system can support. This boom-and-bust cycle can disrupt nitrogen availability during critical stages of crop growth. These rapid shifts in microbial population and activity following carbon inputs are commonly observed in soil systems receiving easily decomposable substrates (Blagodatskaya and Kuzyakov, 2008).
This dynamic becomes especially relevant when considering residue management practices common in Oklahoma. Under no-till or limited-tillage systems, the crop residues have wide carbon-to-nitrogen (C:N) ratios, creating conditions where nitrogen immobilization can occur during the growing season.
Table 1 provides approximate C:N ratios for several crops commonly grown in Oklahoma. When additional carbon is introduced into these systems without accompanying nitrogen, the likelihood of microbial immobilization increases. While immobilization is not bad, it does create a question mark as Oklahoma’s variable climate means the following release of nutrients will be unpredictable.
Table 1. Table depicting the range of C:N ratios for residues of commonly utilized crops in Oklahoma. Ratios were obtained from Brady, N. C., & Weil, R. R. (2017). The Nature and Properties of Soils (15th ed.)
Now consider conventional tillage systems. In Oklahoma, no-till systems typically contain 2 to 3 percent organic matter, which is relatively high given our climate and extended periods of microbial activity. Conventional tillage systems often fall between 0.75 and 2.25 percent organic matter. Because soil organic matter is approximately 58 percent carbon, this represents a substantial difference in the soil carbon pool.
Tillage can temporarily enhance microbial access to both previously mentioned carbon pools. When tillage exposes previously protected carbon, microbial activity increases rapidly. This initial flush can temporarily increase nitrogen mineralization as organic nitrogen is converted to plant-available forms. However, this phase is short-lived. As microbial populations expand, nitrogen demand increases, leading to immobilization and reduced nitrogen availability.
Hypothetically, increased microbial growth and activity would rapidly mineralize organic matter, trigger a surge in NO₃⁻, deplete soil organic matter, and as resources become limiting and the environment can no longer sustain elevated microbial populations, this boom would be followed by a population crash. This relationship is ultimately driven by the soil C:N ratio, which introduces an interesting additional complexity of residue. Different residues bring very different carbon-to-nitrogen balances into the system, and microbes respond accordingly. High carbon residues give microbes plenty of energy but very little nitrogen, so they pull N out of the soil to meet their needs. Residues with lower C:N ratios (soybean, alfalfa, etc.) do opposite, releasing nitrogen as they break down. Now the real question becomes where the critical point sits, and when does management push the system from the threshold of immobilization and mineralization.
These hypotheses form the foundation for new research currently underway through the Precision Nutrient Management Program. Initial proof-of-concept work has already been completed, providing a necessary steppingstone to address these questions.
Figure 1. Graph depicting the different concentrations of nitrate leached corresponding to applied treatments in the proof-of-concept work
The preliminary work (Figure 1) evaluated different sugar sources applied alongside a high-nitrogen product to assess the extent of nitrogen immobilization. Although these studies were conducted using potting soils, clear trends were apparent. Treatments containing sugar consistently showed greater nitrogen immobilization compared to treatments without sugar. This response is consistent with studies showing that additions of simple carbon substrates stimulate microbial growth and increase nitrogen immobilization (Dendooven et al. 2006). Building on this work, an active field-based research project is underway to evaluate how sugar additions influence nitrogen availability and microbial dynamics under real-world Oklahoma production conditions.
From an agronomic standpoint, sugar functions primarily as a readily available carbon source that stimulates microbial growth. In nitrogen-limited systems, this response increases the likelihood that nitrogen will be incorporated into microbial biomass rather than remaining immediately available for crop uptake.
Finally, we conclude with a conceptual consideration. If increased OM mineralization leads to greater plant biomass, this process may partially offset losses of OM. Greater biomass production could return more residues to the soil, contributing to the OM pool in the upper soil profile. Therefore, the system may compensate for OM mineralization through the rebuilding of organic matter via plant inputs. However, the stabilization of this carbon depends on microbial processing and physical protection within the soil matrix (Cotrufo et al. 2015)
However, while the underlying logic is sound, this concept has not been extensively studied within Oklahoma cropping systems. This blog does not address the impact of sugar applications on residue breakdown, and the potential impact of such. Future research through the Precision Nutrient Management Program will further investigate the mineralization process to better understand carbon dynamics within these systems.
Take Home:
- Oklahoma production systems generally have lower residual N and high carbon residues, creating conditions conducive to N immobilization
- Adding sugar increases microbial growth, creating population booms that will momentarily increase mineralization, but then immediately immobilize residual nitrogen.
- Tillage can amplify the negative effects of sugar by exposing more carbon and reducing soil organic matter
- Proof-of-concept work shows sugar triggered a net nitrogen immobilization in a carbon heavy environment
- Proof-of-concept work also suggests that when additional nitrogen is present, sugar additions may shift the system toward net mineralization rather than immobilization.
Work Cited:
Blagodatskaya, E., & Kuzyakov, Y. (2008). Mechanisms of real and apparent priming effects. Biology and Fertility of Soils, 45, 115–131.
Brady, N. C., and R. R. Weil. “The Nature and Properties of Soils, 15th Edn (eBook).” (2017).
Cotrufo, M. F., Wallenstein, M. D., Boot, C. M., Denef, K., & Paul, E. (2013). The Microbial Efficiency-Matrix Stabilization (MEMS) framework. Global Change Biology, 19, 988–995.
Cotrufo, M. F., Soong, J. L., Horton, A. J., Campbell, E. E., Haddix, M. L., Wall, D. H., & Parton, W. J. (2015). Formation of soil organic matter via biochemical and physical pathways of litter mass loss. Nature Geoscience, 8(10), 776–779.
Dendooven, L., Verhulst, N., Luna-Guido, M., & Ceballos-Ramírez, J. M. (2006). Dynamics of inorganic nitrogen in nitrate- and glucose-amended alkaline–saline soil. Plant and Soil, 283(1–2), 321–333.
Devine, M. D., & Hall, L. M. (1990). Implications of sucrose transport mechanisms for the translocation of herbicides. Weed Science, 38(3), 299–304.
Kuzyakov, Y., & Blagodatskaya, E. (2015). Microbial hotspots and hot moments in soil: Concept & review. Soil Biology and Biochemistry, 83, 184–199.
Recous, S., Mary, B., & Faurie, G. (1990). Microbial immobilization of ammonium and nitrate in cultivated soils. Soil Biology and Biochemistry, 22, 913–922.
Monitoring for Cotton Jassid: A Potential New Threat to Oklahoma Cotton
Ashleigh M. Faris, Maxwell Smith, & Jenny Dudak
While the cotton jassid (Amrasca biguttula), also known as the Two-Spot Cotton Leafhopper, has not yet been detected in Oklahoma, its rapid expansion across the Southern Cotton Belt in 2025 makes it a potential threat to the 2026 season. This pest is considered one of the most serious threats to U.S. cotton, with the potential for significant yield losses in untreated fields. Stay informed on if the cotton jassid may be moving from the south and into Oklahoma by signing up for Texas A&M AgriLife Extension text alerts: text COTTON to 833.717.0325.
Identification: The “Two-Spot” Difference
The cotton jassid can be confused with the native potato leafhopper, but its unique markings are the key to early detection (Figure 1).
- Adults: Approximately 1/8 inch (2mm) long, wedge-shaped, and green.
- Key Markings: Look for two small black spots on the crown of the head and one black spot on the tip of each forewing. These spots on the head can sometimes fade but are generally visible under magnification; the spots on the wings will be present in adults and do not fade.
- Nymphs: Wingless and pale green. They are best known for their “crab-like” sideways movement when disturbed on the leaf surface. Any nymphs spotted should warrant a thorough scouting for adult cotton jassids and damage.
Figure 1. Cotton jassid adults (A) have one black dot on each wing and may have two small dots between their eyes (these dots on the crown can fade). The potato leafhopper (B), which is not a threat to cotton production but does occur in Oklahoma, does not have black dots on their wings or between their eyes. Image A courtesy of Isaac Esquivel, UF Extension, image B courtesy of DryBeanAgronomy.ca.
Biology and Host Range
The cotton jassid has a short life cycle, completing a generation in approximately two weeks under warm conditions.
- Reproduction: Eggs are inserted directly into leaf midveins and petioles, hatching in 3–4 days. Eggs will not be visible to the naked eye or through hand lens. Cotton jassids progress through 5 nymphal instars before becoming reproductive adults (Figure 2).
- Host Plants: This pest is polyphagous, meaning it feeds on many hosts. While cotton is a primary target, it also thrives on okra, eggplant, and ornamental hibiscus. It has also been found on native plants like Turk’s cap, as well as weeds like Ceasar weed and Florida pusley.
- 2025 Range on U.S. Cotton: The cotton jassid was detected on cotton in FL, GA, AL, MS, LA, TN, SC, NC, and TX. The TX detections in cotton were limited to southeastern TX in Grimes, Wharton, and Fort Bend counties. At the time of this article’s posting (March 2026), the cotton jassid has not been detected in OK.
Figure 2. Cotton jassid nymphs on the underside of a cotton leaf. Image courtesy of Isaac Esquivel, UF Extension.
Damage: Recognizing Hopperburn
Unlike other leafhoppers, the cotton jassid injects a salivary toxin that disrupts the plant’s vascular system.
- Early Signs: Initial yellowing that resemble potassium deficiency with some upward curling of leaf margins (Figure 3, Rating 1).
- Progression: Characterized by hopperburn, a yellowing (chlorosis) that proceeds from leaf edges and turns red or brown as the tissue dies (Figure 3).
- Systemic Impact: Plants can go downhill quickly, often leading to complete desiccation and stunted growth (Figure 4).
A Hopperburn Injury Rating Scale has been developed by Extension Cotton Entomologists in the mid-South (Figure 3). You cannot let the cotton jassid get ahead of you. Once reddening starts on the leaf margins (Rating 2 in Figure 3) it is likely too late to rescue the cotton plant, damage will quickly progress and photosynthetic capabilities for the plant decline considerably.
Figure 3. Hopperburn injury rating scale for cotton jassid damage. Damage increases from none (0) to severe damage of desiccated leaf (5). Slight yellowing and upward curling of leaf is shown in Rating 1, with increased yellowing, cupping, and beginnings of reddened leaf margins in Rating 2. Insecticide action should be taken prior to reaching Rating 2. Ratings 3 – 5 show increased spread of reddening and desiccation. Images courtesy of Phillip Roberts (UGA Extension) and Scott Graham (AU Extension).
Figure 4. Cotton jassid hopperburn resulting in reddened, dried leaves (A) and stunted cotton plants (B). Image courtesy Isaac Esquivel, UF Extension.
Scouting Protocol
Scouting is mandatory for every cotton field in 2026 to prevent significant yield loss. Plants located at the edge of cotton fields can serve as good indicators, as cotton jassids will enter at field margins where damage is more likely to occur before further in field.
- Target Area: Inspect the undersides of leaves in the mid-to-upper canopy.
- Sample Leaf: Focus on the 4th mainstem leaf below the terminal, as this is where nymphs typically congregate.
- Visual Checks: Because adults fly quickly, count the flightless nymphs. Examine at least 25 leaves per field.
- Threshold: 1 cotton jassid per leaf, or early crop injury indicators (Figure 3, Rating 1) with cotton jassid confirmations nearby.
- Continue Scouting: Since green leaves are needed to fill bolls, growers should scout cotton up to at least 2 weeks prior to defoliation.
Management Guidance
Cultural Practices
- Plant Early: Trials indicate that earlier planting dates can help the crop “outrun” the peak pressure of migrating populations.
- Nutrient Management: Avoid excess Nitrogen, which attracts cotton jassids. Ensure adequate Potassium, as deficient plants crash much faster under cotton jassid stress.
- Varieties: Internationally, varieties with high trichome (hair) density on leaves offer natural resistance to feeding. However, varieties on the U.S. market are generally less hairy than those planted elsewhere. Currently, trials from 2025 do not indicate a varietal difference in terms of cotton jassid susceptibility.
Chemical Control
Based on 2025 research trials conducted by Mid-South Cotton Extension Entomologists, the following insecticides have shown varying levels of control (Table 1). Repeated insecticide applications may be warranted.
Table 1. Suggested foliar insecticides* and their observed control level for suppressing the cotton jassid. Efficacy lasted around 2 weeks.
| Control Level | Insecticides |
| High (>70% Control) | Carbine, Sefina, Sivanto, Bidrin, Venom, Plinazolin |
| Moderate (50-70%) | Transform, Centric, Assail, Orthene |
| Low (<50%) | Steward, Diamond, Bifenthrin, Admire Pro |
*Cotton jassids have shown resistance to every chemistry class in their native range; rotation of modes of action is critical. The mention, listing, or use of specific insecticides is not an endorsement of that product, nor is it a criticism of similar products not mentioned.
If you suspect cotton jassid activity or see hopperburn symptoms, contact the OSU Cotton IPM team: Maxwell Smith (maxwell.smith@okstate.edu), Ashleigh Faris (Ashleigh.faris@okstate.edu), and Jenny Dudak (jdudak@okstate.edu) immediately for confirmation. This team will be monitoring for the cotton jassid and will share updates on nearing threat, Oklahoma detections, and updated management guidance as it becomes available.
For more information on the cotton jassid in the U.S., click on this link to access Extension Factsheets, podcasts, and videos developed by Extension Entomologists managing the pest: https://drive.google.com/file/d/19IFT5c9b5JXEaBgf6X-weya07G56RXS5/view?usp=sharing.
Small Pest, Big Problems: Wheat Curl Mites and Wheat Streak Mosaic Virus Detected in Oklahoma
Ashleigh Faris, Cropping Systems Entomologist, IPM Coordinator
Meriem Aoun, Wheat Pathologist
Department of Entomology & Plant Pathology,
Oklahoma State University
Wheat Curl Mite (WCM) activity has been confirmed in Washita County, located in western Oklahoma. While the mites themselves are difficult to see, they can have a considerable impact on wheat health, primarily due to their role as vectors for several viral diseases such as wheat streak mosaic virus (WSMV). The Plant Disease and Insect Diagnostic Laboratory (PDIDL) has confirmed WSMV in the sample where WCM were detected in Washita County. This week, the PDIDL has also confirmed infection by WSMV in Blaine County (Canton, OK), McCurtain County (Garvin, OK), and Cleveland County (Noble, OK).
Identification
The Wheat Curl Mite is nearly invisible to the naked eye. At approximately 1/100 of an inch long, these pests require a 10x – 20x hand lens for proper identification.
- Appearance: They are white or cream-colored, cigar-shaped (cylindrical), and possess only four legs located near the head (Figure 1).
- Behavior: They are typically found in the protected areas of the plant, such as developing, youngest leaves or the furrows of the leaf surface. As the leaf unfurls, the mites migrate to the next emerging leaf.
Figure 1. Wheat curl mites and eggs on a wheat leaf (A, B), and mites on a maturing wheat kernel (C). Images courtesy G. Bauchan and R. Ochoa, USDA-ARS.
Biology and Life Cycle
Understanding the WCM life cycle is critical for preventative management:
- Rapid Reproduction: Under optimal temperatures (75° – 85°F), a WCM can complete its life cycle in 7 to 10 days. This allows populations to explode rapidly during warm autumns or springs.
- Dispersal: WCMs cannot fly; they rely entirely on wind currents to move from plant to plant or field to field. They crawl to the tips of leaves and hitchhike on the wind.
- Survival (The Green Bridge): WCMs are obligate parasites, meaning they require living green tissue to survive and reproduce. They persist through the summer on volunteer wheat and various perennial or annual grasses. This is known as the green bridge. If this bridge is not broken, mites move into the newly planted crop in the fall.
Damage and Virus Transmission
WCMs cause two types of damage:
- Direct Feeding: Mites suck sap from the leaf cells. This causes the edges of the leaf to roll inward (the curl part of WCM) (Figure 2). This curling provides a protected microclimate for the mites to reproduce. Heavy infestations can cause stunting and a slowed appearance in growth.
- Viral Vector (Primary Concern): The WCM is the sole vector for Wheat Streak Mosaic Virus (WSMV), High Plains Wheat Mosaic Virus (HPWMoV), and Triticum Mosaic Virus (TriMV).
- Symptoms: Infected plants show yellowing, mottled or streaked leaves, and severe stunting (Figures 3 & 4).
- Impact: If infection occurs in the fall, yield loss can be up to 100%. Spring infections are generally less damaging.
Scouting Techniques
Because the mites are so small, scouting focuses on leaf symptoms and having a hand lens:
- Check your Fields: Examine the youngest leaves of the wheat plant. Look for the characteristic inward rolling of the leaf edges (Figure 2).
- Use Magnification: Slowly unroll a suspect leaf and use a hand lens to look for tiny, white, slow-moving specks in the leaf furrows.
- Pattern of Infestation: Wind-dispersed mite infestations often start at the edge of a field (particularly edges adjacent to volunteer wheat or CRP land) and move inward in the direction of prevailing winds. Areas with infestations may show signs of yellowing and appear as patches distributed at random across the field (Figure 4).
Figure 2. Infestation of wheat curl mites on wheat results in tightly curled leaves and entrapment of subsequent leaves within the curl (A). After full leaf emergence, a tight curl at the leaf edge remains (B). Images courtesy of UNL Extension.
Figure 3. Wheat streak mosaic virus (WSMV) symptoms includeyellowing, mottled or streaked leaves. Image courtesy of Meriem Aoun, Oklahoma State University.
Figure 4. Plants at field margins, neighboring a wheat curl mite source, are the first to become infected with viruses of the Wheat Streak Mosaic Virus (WSMV) complex and develop symptoms, such as yellowing and streaking. Notice the gradient in color from the field edge (left) toward the center of the wheat field. Image courtesy of UNL Extension.
Management Recommendations
Currently, there are no effective rescue chemical treatments for WCM once symptoms appear in the field. Miticides generally do not reach the mites hidden inside the curled leaves. Management must be proactive:
- Manage volunteer wheat and grassy weeds: This is the most effective management tool to break the green bridge. Ensure all volunteer wheat and grassy weeds are completely dead (via tillage or herbicide) at least two weeks prior to planting the new crop. WCMs will starve within days without a living host.
- Delayed Planting: Planting wheat later in the fall reduces the window of time that mites must migrate into the crop and slows their reproduction rate as temperatures drop.
- Variety Selection: Some wheat varieties offer resistance or tolerance to WCM or WSMV. Consult the latest OSU variety trial data to select adapted varieties for north-central Oklahoma that carry these traits. Currently, Breakthrough is the most resistant OSU variety, which carries the WSMV resistance gene, Wsm1.
Brown Wheat Mite Activity in North Central Oklahoma
Ashleigh Faris, Cropping Systems Entomologist, IPM Coordinator
Department of Entomology & Plant Pathology,
Oklahoma State University
Following a period of dry weather, wheat growers in central Oklahoma are reporting activity of the Brown Wheat Mite (BWM). Unlike many other wheat pests, BWM thrives in drought conditions, and its damage can often be mistaken for moisture stress or nutrient deficiency.
Identification
The Brown Wheat Mite is small—about the size of a needle point—but is generally easier to spot than the Wheat Curl Mite because it is active on the leaf surface.
- Appearance: BWM has a dark red to brownish-black, oval-shaped body (Figure 1).
- Distinguishing Feature: Its front legs are significantly longer than its other three pairs of legs.
- Behavior: They are most active during the day, particularly in the afternoon, and will quickly drop to the ground if the plant is disturbed (Figure 2).
Figure 1. Brown wheat mite (BWM).
Figure 2. Brown wheat mites (BWM) on wheat. Image courtesy L. Galvin, OSU Extension.
Biology and Life Cycle
BWM populations consist entirely of females that produce offspring without mating (parthenogenesis), allowing for extremely rapid population growth under dry conditions. The BWM has a unique life cycle in that it can lay two types of eggs. Environmental conditions dictate when these two types of eggs are laid:
- Red Eggs: Laid during the growing season and hatch in about a week when conditions are favorable.
- White (Diapause) Eggs: Laid as temperatures rise and the crop matures. They are highly resistant and allow the population to survive the summer heat, hatching only when cooler, wetter weather arrives in the fall.
Damage
BWM damage is caused by the mites piercing plant cells and sucking out the plant nutrients.
- Symptoms: Initial damage appears as “stippling” (fine white or yellow spots) on the leaves. As feeding continues, leaves take on a silvery or bronzed appearance (Figure 3).
- Tipping: Heavy infestations cause the tips of the leaves to turn brown and die.
- Weather Interaction: Damage is most severe when plants are already under drought stress. Because both BWM damage and drought cause yellowing/browning, it is essential to confirm the presence of mites before treating.
Figure 3. Brown wheat mite (BWM) damage.
Scouting
Because BWM is highly mobile and drops when disturbed, careful scouting is required:
- Timing: Scout during the warmest part of the day when mites are most active on the upper leaves.
- The Paper Test: Gently but quickly shake or tap wheat plants over a white piece of paper or a white clipboard. Look for tiny dark specks moving across the surface.
- Economic Threshold: While thresholds vary based on crop value and moisture stress, research suggests a treatment threshold of 25 to 50 brown wheat mites per leaf in wheat that is 6 inches to 9 inches tall is economically warranted. An alternative estimation is “several hundred” per foot of row. If the wheat is severely stressed, the lower end of that threshold should be used.
Management Recommendations
- The “Rain” Factor: A significant, driving rain is often the most effective control for BWM. Rain can physically knock mites from the plant and promote fungal pathogens that naturally reduce the population.
- Chemical Control: If populations exceed the threshold and no rain is in the forecast, chemical intervention may be necessary. Know the cost of the treatment and value of your wheat so you can determine if an application is a worth return on investment.
- Effective Ingredients: Organophosphates (such as Dimethoate) have historically provided better control than many pyrethroids, as the latter can sometimes result in mite “flaring” or simply fail to provide adequate residual control.
- Coverage: High water volume is critical to ensure the insecticide reaches the mites, especially if they have moved toward the base of the plant.
- Pre-harvest Intervals & Grazing Restrictions: Always read and follow the label guidelines. For more on acaricides that can be applied in wheat see the Oklahoma State University Fact Sheet “Management of Insect and Mite Pests in Small Grains” (CR-7194).
- Cultural Practices: Since BWM thrives in dry, dusty conditions, maintaining good soil moisture and vigorous plant growth can help the crop tolerate feeding. Here’s to hoping for some rain soon in the forecast; we could really use it for lots of reasons in Oklahoma.
Check Your Wheat: Greenbugs Reported in Central Oklahoma
Ashleigh M. Faris
Cropping Systems Extension Entomologist
Department of Entomology & Plant Pathology
Oklahoma State University
Wheat producers in central Oklahoma are reporting the presence of the greenbug, Schizaphis graminum, in winter wheat fields. Greenbugs are one of the most important insect pests of wheat in the southern Great Plains and can occur from fall through spring. These aphids feed on plant sap and inject toxins into wheat plants, causing characteristic leaf discoloration and plant injury.
Early detection through field scouting is essential to determine whether populations are increasing and if an insecticide treatment is justified.
Greenbug Identification & Biology
Key identifying characteristics of greenbug (Figure 1):
- Small aphids (~1/16 inch long)
- Pale to lime-green body
- Dark green stripe down the middle of the back
- Dark tips on antennae and legs
- Found in colonies on the underside of wheat leaves
Greenbugs reproduce rapidly under favorable conditions (between 55° F and 95° F) and often occur in patches within fields rather than evenly distributed populations. During periods of cool weather, the greenbug may increase to enormous numbers, due to the absence of natural enemies, which develop significantly slower compared to greenbugs at such temperatures. On the other hand, cold weather can also influence aphid populations. However, this latest cold snap is not enough to eliminate greenbugs. It takes average temperatures below 20° F for at least a week to kill a substantial number of greenbugs in wheat.
Greenbug Damage in Wheat
Greenbugs damage wheat in two ways, through direct feeding and injection of toxic saliva. Greenbugs may also transmit barley yellow dwarf virus (BYDV), which can further reduce yield potential.
Typical early symptoms include small, reddish or copper spots on leaves (Figure 2) and yellowing around feeding sites. Advanced infestations will result in leaves turning yellow or orange, dead leaf tissue, stunted plants, and expanding patches of dead wheat. Heavy infestations may kill seedlings and reduce tillering, particularly during drought stress.
How to Scout for Greenbugs
The Glance-N-Go™ sampling system developed by Oklahoma State University can help determine whether aphid populations exceed economic thresholds. Download the Greenbug Glance N’ Go Sampler app for your smartphone. You will then input the control cost ($/Acre), crop value ($/Acre), and the Spring sampling window. Use a zig-zag or W-pattern (Figure 3) to scout your field, checking undersides of leaves at three tillers per stop for greenbugs and brown mummies. Use the app to record the numbers of these insects and sample until the app tells you to stop sampling or tells you treat. As temperatures warm, continue to scout regularly as greenbug populations may build.
Scouting recommendations without the Greenbug Glance N’ Go Sampler app:
- Walk a W or zigzag pattern across the field.
- Examine 10–20 plants at each stop.
- Check:
- Underside of leaves
- Leaf midrib
- Base of tillers
- Record:
- Aphids per tiller
- Presence of aphid mummies (Figure 4)
- Beneficial insects
Beneficial Insects
Natural enemies frequently control aphid populations. While scouting for greenbug you should also look for lady beetles, lacewing larvae, hoverfly larvae, and parasitized aphids (“mummies”) (Figure 4). If beneficial insects are abundant, aphid populations may decline without insecticide treatment. Where there are one to two lady beetles (adults and larvae) per foot of row, or 15 to 20 percent of the greenbugs have been parasitized, control measures could be delayed until it is determined whether the greenbug population is continuing to increase.
Based on current wheat scouting, it appears that parasitoid numbers are low this 2026 season so continuing to scout for greenbug will be critical in responding to populations that go unchecked by beneficials.
Economic Threshold Guidelines
The simplest way to determine if action needs to be taken against greenbugs is to utilize the Glance-N-Go™ sampling system developed by Oklahoma State University. Approximate guidelines historically used in Oklahoma wheat can be found in Table 1 below.
Thresholds are influenced by:
- Wheat growth stage
- Crop value
- Cost of treatment
- Presence of beneficial insects
Insecticides Labeled for Greenbugs in Wheat
Aphid feeding and insecticide performance are strongly influenced by temperature. Greenbugs tend to move higher on wheat plants during warm conditions but may move lower on the plant or below ground during cold weather, reducing exposure to insecticides. As a result, damaging populations are most often observed in late winter and early spring. Insecticides generally perform best when temperatures are above 50°F, and control may occur more slowly in cooler conditions (e.g., control at 45° F may take roughly twice as long as at 70° F). If applications must be made under cooler temperatures, use the highest labeled rate. Wheat grown under irrigation can typically tolerate higher greenbug populations than dryland wheat.
Always follow pesticide label directions, application sites, and rates. Be sure to read and follow the label for preharvest intervals (PHI) and restricted-entry intervals (REI). Use a minimum of 10 GPA by ground and 3 GPA by air (if labelled for aerial application) to ensure adequate coverage.
For assistance with aphid identification or treatment decisions, see OSU Fact Sheet EPP-7099 Small Grain Aphids in Oklahoma and Their Management, or contact your local OSU Extension office.
One Well-Timed Shot: Rethinking Split Nitrogen Applications in Wheat production
Brian Arnall, Precision Nutrient Management Specialist
Samson Abiola, PNM Ph.D. Student.
Nitrogen is the most yield limiting nutrient in wheat production, but it’s also the most unpredictable. Apply it too early, and you risk losing it to leaching or volatilization before your crop can use it. Apply it too late, and your wheat has already determined its yield potential; you’re just feeding protein at that point. For decades, the conventional wisdom has been to split nitrogen applications: put some down early to get the crop going, then come back later to apply again. But does splitting actually work? And more importantly, when is the optimal window to apply nitrogen if you want to maximize both yield and protein quality? We spent three years across different Oklahoma locations testing every timing scenario to answer these questions.
How We Tested Every Nitrogen Timing Scenario in Oklahoma Wheat
Between 2018 to 2021, we conducted field trials at three Oklahoma locations, including Perkins, Lake Carl Blackwell, and Chickasha, representing different soil types and growing conditions across the state. We tested three nitrogen rates: 0, 90, and 180 lbs N/ac, applied as urea at five critical growth stages based on growing degree days (GDD). These timings were 0 GDD (preplant, before green-up), 30 GDD (early tillering), 60 GDD (active tillering), 90 GDD (late tillering, approximately Feekes 5-6), and 120 GDD (stem elongation, approaching jointing). We also compared single applications at each timing against split applications, where half the nitrogen (45 lbs N ac-1) went down preplant, and the other half was applied in-season (45 lbs N ac-1).
The Sweet Spot: Yield and Protein at the 90 lbs N/ac Rate
Across all site-years, at the 90 lbs N/ac rate, timing had a significant impact on both yield and protein. The highest yields came from the 30 and 90 GDD timings, producing 62 to 66 bu/ac, with 60 GDD reaching the peak (Figure 1). Protein at these early timings stayed relatively modest at 13%. The 90 GDD timing delivered 62 bu/ac with 14% protein matching the yield of the 30 GDD application but pushing protein a percentage higher (Figure 2). The real problem appeared at 120 GDD. Delaying application until stem elongation dropped yields to just 49 bu/ac, even though protein climbed to 15%. That’s a 13 bushel penalty compared to the 90 GDD timing. At current wheat prices per bushel, that late application may cost farmers over $100 per acre in lost revenue. By 120 GDD, the crop has already determined its yield potential tillers are set, head numbers are locked in and nitrogen applied at this stage can only be directed toward protein synthesis, not building more yield components.
More Nitrogen Does not lead to high yield
Doubling the nitrogen rate to 180 lbs N/ac revealed something critical, more nitrogen doesn’t mean more yield. The yield pattern remained nearly identical to the 90 lbs N/ac rate. The 60 GDD timing produced the highest yield at 68 bu/ac, followed closely by 30 GDD at 67 bu/ac. The 90 GDD timing yielded 62 bu/ac, and the 120 GDD timing again crashed to 51 bu/ac. The only difference between the two rates was protein concentration (Figure 2). At 180 lbs N/ac, protein levels increased across all timings: 13% at preplant, 15% at both 30 and 60 GDD, 15-16% at 90 GDD, and 16% at 120 GDD. This confirms a fundamental principle: once farmers supply enough nitrogen to maximize yield potential, which occurred at 90 lbs N/ac in these trials, additional nitrogen only increases grain protein. It does not build more bushels. Unless farmers are receiving premium payments for high-protein wheat, that extra 90 lbs of nitrogen represents a cost with no yield return.
Should farmers split their nitrogen application?
Now that timing has been established as critical, the next question becomes: should farmers split their nitrogen applications, or is a single application sufficient? The conventional recommendation has been to split nitrogen apply part preplant to support early growth and tillering, then return with a second application later in the season to boost protein and finish the crop. But does the data support this practice? We compared three strategies at each timing: applying all nitrogen preplant, applying all nitrogen in-season at the target timing, or splitting nitrogen equally between preplant and in-season timing. The goal was to determine whether the extra trip across the field will deliver better results.
Our findings revealed that splitting provided no consistent advantage. At 30 GDD, all three strategies preplant, in-season, and split performed identically, producing 62-65 bu/ac with 12-13% protein (Figure 3 and 4). No statistical differences existed among them. At 60 GDD, similar pattern was held. Yields ranged from 61 to 66 bu/ac and protein stayed at 12-13% regardless of whether farmers applied all nitrogen preplant, all at 60 GDD, or split between the two. At 90 GDD, the single in-season application actually outperformed the split. While yields remained similar across all three methods (61-64 bu/ac), the in-season application delivered significantly higher protein at 13.7% compared to 12.4% for preplant and 12.5% for split applications. This suggests that concentrating nitrogen at 90 GDD, rather than diluting it across two applications, allows more efficient incorporation into grain protein. The only timing where splits appeared beneficial was 120 GDD, where the split application yielded 59 bu/ac compared to 51 bu/ac for the single late application. But this is not a win for splitting, it simply demonstrates that applying all nitrogen at 120 GDD is too late and putting half down earlier salvages some of the yield loss. Across all timings tested, splitting nitrogen into two applications offered no agronomic advantage over a single well-timed application, meaning farmers are making an extra pass for no gain in yield or protein.
Practical Recommendations for Nitrogen Management
Based on three years of field data, farmers should target the 90 GDD timing (late tillering, Feekes 5-6) for their main nitrogen application to achieve the best balance between yield and protein. This window typically falls in late February to early March in Oklahoma, though farmers should monitor crop development rather than relying solely on the calendar apply when wheat shows multiple tillers, good green color, and vigorous growth. A rate of 90 lbs N/ac maximized yield in these trials; higher rates only increased protein without adding bushels, so farmers should only exceed this rate if receiving premium payments for high-protein wheat. Splitting nitrogen applications provided no advantage at any timing, meaning a single well-timed application at 90 GDD is sufficient for most Oklahoma wheat production systems. The exception would be sandy soils with high leaching potential, where splitting may reduce nitrogen loss. Farmers should avoid delaying applications until 120 GDD or later, as this timing consistently resulted in 15-25 bushel per acre yield losses even though protein increased. For farmers specifically targeting premium protein markets, a two-step strategy works best: apply 90 lbs N/ac at 90 GDD to establish yield potential and baseline protein, then follow with a foliar application of 20-30 lbs N/ac at flowering to push protein above 14% without sacrificing yield. Finally, weather conditions matter hot, dry forecasts increase volatilization risk and reduce uptake efficiency, so farmers should consider moving applications earlier if low humidity conditions are expected.
Split Application Caveat * Note from Arnall.
The caveat to the it only takes one pass, is high yielding >85+ bpa, environments. In these situation I still have not found any value for preplant nitrogen application. I have seen however a split spring application is valuable. Basically putting on 30-50 lbs at green-up, with the rest following at jointing (hollowstem). The method tends to reduce lodging in the high yielding environments.
This work was published in Front Plant Sci. 2025 Nov 6;16:1698494. doi: 10.3389/fpls.2025.1698494
Split nitrogen applications provide no benefit over a single well timed application in rainfed winter wheat
Another reason to N-Rich Strip.
Yet just one more data set showing the value of in-season nitrogen and why the N-Rich Strip concept works so well.
Questions or comments please feel free to reach out.
Brian Arnall b.arnall@okstate.edu
Acknowledgements:
Oklahoma Wheat Commission and Oklahoma Fertilizer Checkoff for Funding.
Double Crop Options After Wheat (KSU Edition)
Stolen from the KSU e-Update June 5th 2025.
Double cropping after wheat harvest can be a high-risk venture for grain crops. The remaining growing season is relatively short. Hot and/or dry conditions in July and August may cause problems with germination, emergence, seed set, or grain fill. Ample soil moisture this year can aid in establishing a successful crop after wheat harvest. Double-cropping forages after wheat works well even in drier regions of the state.
The most common double crop grain options are soybean, sorghum, and sunflower. Other possibilities include summer annual forages and specialized crops such as proso millet or other short-season summer crops, even corn. Cover crops are also an option for planting after wheat (see the companion eUpdate article “Cover crops grown post-wheat for forage”).
Be aware of herbicide carryover potential
One major planting consideration after wheat is the potential for herbicide carryover. Many herbicides applied to wheat are Group 2 herbicides in the sulfonylurea family with the potential to remain in the soil after harvest. If a herbicide such as chlorsulfuron (Glean, Finesse, others) or metsulfuron (Ally) has been used, then the most tolerant double crop will be sulfonylurea-resistant varieties of soybean (STS, SR, Bolt) or other crops. When choosing to use herbicide-resistant varieties, be sure to match the resistance trait with the specific herbicide (not only the herbicide group) that you used. This is especially true when looking at sunflowers as a double crop. There are sunflowers with the Clearfield trait, which allows Beyond herbicide applications, and ExpressSun sunflowers, which allow an application of Express herbicide. While both of these herbicides are Group 2 (ALS-inhibiting herbicides), the Clearfield trait and ExpressSun are not interchangeable, and plant damage can result from other Group 2 herbicides.
Less information is available regarding the herbicide carryover potential of wheat herbicides to cover crops. There is little or no mention of rotational restrictions for specific cover crops on the labels of most herbicides. However, this does not mean there are no restrictions. Generally, there will be a statement that indicates “no other crops” should be planted for a specified amount of time, or that a bioassay must be conducted prior to planting the crop.
Burndown of summer annual weeds present at planting is essential for successful double-cropping. Assuming glyphosate-resistant kochia and pigweeds are present, combinations of glyphosate with products such as saflufenacil (Sharpen) or tiafenacil (Reviton), or alternative treatments such as paraquat may be required. Dicamba or 2,4-D may also be considered if the soybean varieties with appropriate herbicide resistance traits are planted. In addition, residual herbicides for the double crop should be applied at this time.
Management, production costs, and yield outlooks for double crop options are discussed below.
Soybeans
Soybeans are likely the most commonly used crop for double cropping, especially in central and eastern Kansas (Figure 1). With glyphosate-resistant varieties, often the only production cost for planting double crop soybeans was the seed, an application of glyphosate, and the fuel and equipment costs associated with planting, spraying, and harvesting. However, the spread of herbicide-resistant weeds means additional herbicides will be required to achieve acceptable control and minimize the risk of further development of resistant weeds.
Weed control. The weed control cost cannot really be counted against the soybeans, since that cost should occur whether or not a soybean crop is present. In fact, having soybeans on the field may reduce herbicide costs compared to leaving the field fallow. Still, it is recommended to apply a pre-emergence residual herbicide before or at planting time. Later in the summer, a healthy soybean canopy may suppress weeds enough that a late-summer post-emergence application may not be needed.
Variety selection for double cropping is important. Soybeans flower in response to a combination of temperature and day length, so shifting to an earlier-maturing variety when planting late in a double crop situation will result in very short plants with pods that are close to the ground. Planting a variety with the same or perhaps even slightly later maturity rating (compared to soybeans planted at a typical planting date) will allow the plant to develop a larger canopy before flowering. Planting a variety that is too much later in maturity, however, increases the risk that the beans may not mature before frost, especially if long periods of drought slow growth. The goal is to maximize the length of the growing season of the crop, so prompt planting after wheat harvest time is critical. The earlier you can plant, the higher the yield potential of the crop if moisture is not a limiting factor.
Fertilizer considerations. Adding some nitrogen (N) to double-crop soybeans may be beneficial if the previous wheat yield was high and the soil N was depleted. A soil test before wheat harvest for N levels is recommended. Use no more than 30 lbs/acre of N. It would be ideal to knife-in the fertilizer. If that is not possible, banding it on the soil surface would be acceptable. Do not apply N in the furrow with soybean seed as severe stand loss can occur.
Seeding rates and row spacing. Seeding rate can be slightly increased if soybeans are planted too late in order to increase canopy development. Narrow row spacing (15-inch or less) has often resulted in a yield advantage compared to 30-inch rows in late plantings. Soybeans planted in narrow rows will canopy over more quickly than in wide rows, which is important when the length of the growing season is shortened. Narrow rows also offer the benefits of increasing early-season light capture, suppressing weeds, and reducing erosion. On the other hand, the advantage of planting in wide rows is that the bottom pods will usually be slightly higher off the soil surface to aid harvest. The other consideration is planting equipment. Often, no-till planters will handle wheat residue better and place seeds more precisely than drills, although the difference has narrowed in recent years.
What are typical yield expectations for double-crop soybeans? It varies considerably depending on moisture and temperature, but yields are usually several bushels less than full-season soybeans. A long-term average of 20 bushels per acre is often mentioned when discussing double-crop soybeans in central and northeast Kansas. Rainfall amount and distribution can cause a wide variation in yields from year to year. Double-crop soybean yields typically are much better as you move farther southeast in Kansas, often ranging from 20 to 40 bushels per acre.
A recent publication explores the potential yield of double-crop soybeans relative to full-season yield (Figure 2) and the most limiting factors affecting the yields for double-crop soybeans. The link to this article is: https://bookstore.ksre.ksu.edu/pubs/MF3461.pdf.
Grain Sorghum
Grain sorghum is another double crop option. Unlike soybeans, sorghum hybrids for double cropping should be earlier maturing hybrids. Sorghum development is primarily driven by the accumulation of heat units, and the double crop growing season is too short to allow medium-late or late hybrids to mature before the first frost in most of Kansas.
Seeding rates and row spacing. Late-planted sorghum likely will not tiller as much as early plantings and can benefit from slightly higher seeding rates than would be used for sorghum planted at an earlier date. Narrow row spacing is advised, especially if the outlook for rainfall is good.
Fertilizer considerations. A key component for the estimation of N application rates is the yield potential. This will largely determine the N needs. It is also important to consider potential residual N from the wheat crop. This can be particularly important when wheat yields are lower than expected. In that situation, additional available N may be present in the soil. Assess the amount of profile N by taking soil samples at a depth of 24 inches and submitting them for analysis at a soil testing laboratory.
Double crop sorghum planted into average or greater-than-average amounts of wheat residue can result in a challenging amount of residue to deal with when planting next year’s crop. Nitrogen fertilizer can be tied up by wheat residue, so use application methods to minimize tie-up, such as knifing into the soil below the residue.
Weed control. Weed control can be important in double-crop sorghum. Warm-season annual grasses, such as crabgrass, can reduce double-crop sorghum yields. Using a chloroacetamide-and-atrazine pre-emergence product may be key to successful double-crop sorghum production. Herbicide-resistant grain sorghum varieties will allow the use of imazamox (Imiflex in igrowth sorghums) or quizalofop (FirstAct in DoubleTeam grain sorghum) that can control summer annual grasses.
No-till studies at Hesston documented 4-year average double crop sorghum yields of 75 bushels per acre compared to about 90 bushels per acre for full-season sorghum. A different 10-year study that did not have double crop planting but did compare early- and late-planting dates averaged 73 bushels per acre for May planting vs. 68 bushels per acre for June planting.
Sunflowers
Sunflowers can be a successful double crop option anywhere in the state, provided there is enough moisture at planting time to get a stand. Sunflowers need more moisture than any other crop to germinate and emerge because of the large seed. Therefore, stand establishment is important. Planting immediately after wheat harvest on a limited irrigation field can be a good fit to help with stand establishment.
Seeding rates and hybrid selection. When double-cropping sunflowers, producers should use similar seeding rates to what is typical for the area for full-season sunflowers. While full-season sunflowers can be successful in double-crop production, utilizing shorter-season hybrids can increase the likelihood of the sunflowers blooming and maturing before a killing frost.
Weed control. First, it is important to check the herbicide applications on the wheat. The rotation restriction to sunflowers after several commonly used wheat herbicides is 22-24 months.
Weed control can be an issue with double-crop sunflowers since herbicide options are limited, especially post-emergence. Thus, controlling weeds prior to sunflower planting is critical and may be complicated pre-plant restrictions for some herbicides. Planting Clearfield or ExpressSun sunflowers will provide additional post-emergence herbicide options, but ALS-resistant kochia and pigweeds still won’t be controlled. Imazamox (Beyond in Clearfield sunflower) has activity on small annual grasses as well as many broadleaf weeds, if they are not ALS-resistant.
Summer annual forages
With mid-July plantings, and where herbicide carryover issues are not a concern, summer annual sorghum-type forages are also a good double crop option. A study planted July 21, 2008 near Holton, when summer rainfall was very favorable, provided yields of 2.5 to 3 tons dry matter/acre for hybrid pearl millet and sudangrass at the low end to 4 to 5 tons dry matter/acre for forage sorghum, BMR forage sorghum, photoperiod sensitive forage sorghum, and sorghum x sudangrass hybrids. Earlier plantings may produce even more tonnage, as long as there is adequate August rainfall.
One challenge with late-planted summer annual forages is getting them to dry down when harvest is delayed until mid- to late-September. Wrapping bales or bagging to make silage are good ways to deal with the higher moisture forage this late in the year.
Corn
Is double-crop corn a viable option? Corn is typically not recommended for late June or July plantings because yield is usually substantially less than when planted earlier.
Typically, mid-July planted corn struggles during pollination and seldom receives sufficient heat units to fill grain before frost. Very short-season corn hybrids (80 to 95 RM) have the greatest chance of maturing before frost in double crop plantings, but generally have less yield potential when compared to hybrids of 100 RM or more used for full-season plantings. Short-season hybrids often set the ear fairly close to the ground, increasing the harvest difficulty. Glyphosate-resistant hybrids will make weed control easier with double crop corn, but problems remain present with late-emerging summer weeds such as pigweeds, velvetleaf, and large crabgrass. Keep in mind, corn is very susceptible to carryover of most residual ALS herbicides used in wheat.
Considerations for altering seeding rates and variety/hybrid maturity for the crops discussed above are summarized in Table 1.
Table 1. Seeding rate and variety/hybrid relative maturity considerations for double crops compared to full-season.
| Crop | Seeding rate | Relative maturity |
| ???????? Difference between double crop and full-season ???????? | ||
| Soybean | Increase | No change or longer |
| Sorghum | Increase | Shorter |
| Sunflower | No change | Shorter |
| Corn | No change | Shorter |
Volunteer wheat control
One of the issues with double cropping that is often overlooked by producers is the potential for volunteer wheat in the crop following wheat. If volunteer wheat emerges and goes uncontrolled, it can cause serious problems for nearby wheat fields in the fall as a host for the wheat streak mosaic complex of viruses [wheat streak mosaic (WSMV), High Plains disease (HPD), and triticum mosaic (TriMV)] that are transmitted by the wheat curl mite (WCM).
Volunteer wheat can generally be controlled fairly well with glyphosate or Group 1 herbicides such as quizalofop (Assure II, others), clethodim (Select Max, others), or sethodydim (Poast Plus, others), but control is reduced during times of drought stress. Atrazine can provide control of volunteer wheat in double-crop corn or sorghum, but control can be erratic depending on rainfall patterns.
For more detailed information about herbicides, see the “2025 Chemical Weed Control for Field Crops, Pastures, and Noncropland” guide available online at https://www.bookstore.ksre.ksu.edu/pubs/CHEMWEEDGUIDE.pdf or check with your local K-State Research and Extension office for a paper copy. The use of trade names is for clarity to readers and does not imply endorsement of a particular product, nor does exclusion imply non-approval. Always consult the herbicide label for the most current use requirements.
To Subscribe to the KSU Agronomy E-Updates follow this link
https://eupdate.agronomy.ksu.edu/index_new_prep.php
Authors contributing to the post
Sarah Lancaster, Weed Management Specialist
slancaster@ksu.edu
John Holman, Cropping Systems Agronomist
jholman@ksu.edu
Logan Simon, Southwest Area Agronomist
lsimon@ksu.edu
Tina Sullivan, Northeast Area Agronomist
tsullivan@ksu.edu
Jeanne Falk Jones, Multi-County Agronomist
jfalkjones@ksu.edu
Boosting Wheat Grain Protein: Smart Spray Strategies for Better Grain Quality
Brian Arnall, Precision Nutrient Management Specialist
Samson Abiola, PNM Ph.D. Student.
Wheat Protein and Technology challenge
For wheat growers, achieving both high yields and good protein content is a constant challenge. Wheat contributes about 20% of the world’s calories, making it a vital crop for global nutrition. Every season, we face the question of how to boost grain protein concentration (GPC) without sacrificing the yield.
Traditional approaches often involve applying more nitrogen (N) early in the season. While this can help, it is often wasteful, environmentally problematic, and does not always translate to higher protein levels at harvest. The effectiveness of N applications depends not just on timing but also on the spray technology used, including the N source, nozzle type, and droplet size. While protein premiums are never guaranteed, we wanted to develop recommendations prior to the need.
The Research Approach: Timing and Technology
Our research team conducted a comprehensive three-year study (2019-2022) across three Oklahoma locations (Perkins, Lake Carl Blackwell, and Chickasha) to investigate how different combinations of N sources, nozzle types, and droplet sizes affect protein when applied during flowering. We considered two N sources (urea-ammonium nitrate (UAN) and aqueous urea [Aq. Urea]). We also evaluated three nozzle types: Standard flat fan (FF) nozzles with a traditional 110° spray angle, 3D nozzles with three-dimensional spray patterns that enhance canopy penetration, Twin (TW) nozzles with dual forward and rear facing sprays (30° forward and backward)
Finally, we tested both fine droplets (below 141 microns) and coarse droplets (≥141 microns). All applications were made at flowering i.e., when you start seeing yellow anthers sticking out of the wheat heads. Both UAN and Aq. urea were applied at a 20 gpa application rate with a 1:1 dilution with water delivering approximately 30 lbs. of N per acre.
What We Found: More Protein Without Hurting Yield
The big news? Spraying N at flowering boosted wheat protein by 12% without sacrificing yield. This held true across fields yielding anywhere from 30 to 86 bushels per acre. Why doesn’t it hurt yield? By flowering time, your wheat has already “decided” how many heads and kernels it will produce. The N you spray at this stage goes straight to building protein in those existing kernels.
One important caution: Mother Nature still calls the shots, so keep an eye on the forecast before planning your application. If the weather is hot and dry, this is not a good idea. First, those environments typically result in higher protein anyways. But low humidity will significantly increase the likelihood of burn.
Lake Carl Blackwell Findings: UAN Takes the Lead
At our Lake Carl Blackwell site, we saw our highest protein levels reaching up to 16.3% in some plots. In 2020-21, UAN clearly beat Aq. urea (14.7% vs. 14.0% protein). Both were much better than not applying any N at flowering (13.1%) (Figure 1A). Also, the 3D nozzle gave us the highest protein (14.7%), outperforming the control but performing similarly to FF (14.0%) and TW nozzles (14.2% (Figure 1B). The next year (2021-22) showed us something interesting, the combination of N source and droplet size really matters. UAN with fine droplets hit 14.6% protein, similar to UAN with coarse droplets (14.4%) and Aq. urea with coarse droplets (14.3%), but Aq. urea with fine droplets fell behind at just 13.8% (Figure 1C).
Chickasha Results: Matching Your N to the Right Droplet Size
At Chickasha, protein ranged from 10.1% to 13.8% across the two years we studied. In 2021-22, UAN beat Aq. urea (12.7% vs. 12.2%), and both beat the control (11.8%) (Figure 2A). Also, the 3D nozzle (12.8%) outperformed both FF and TW nozzles (both 12.2%) (Figure 2B).
In 2020-21, we found that the combination of N source, nozzle type, and droplet size all worked together to affect protein. The winning combination was UAN with 3D nozzle and fine droplets (13.23% protein), which performed similarly to Aq. urea with TW nozzle and coarse droplets (13.18%) (Figure 2C). The least performer was Aq. urea with TW nozzles and fine droplets (12.20%) among the treatments. This shows how weather and growing conditions can change which factors matter most from year to year
Perkins Results: Getting Every Detail Right
At our Perkins site, we saw protein levels ranging from 10% to 13.1%. Here, the combination of all three factors (N source, nozzle type, and droplet size) made a huge difference. The best setup was UAN with 3D nozzle and coarse droplets (12.2% protein). The worst was Aq. urea with TW nozzle and fine droplets (10.5%) (Figure 3). That’s a 15% difference that could mean the difference between premium and feed-grade wheat!
UAN consistently outperformed Aq. Urea across all setups. For example, UAN with 3D nozzle and coarse droplets produced 10% higher protein than the same setup with Aq. Urea.
Equipment and Application Recommendations
Over the three years UAN consistently outperformed perform Aq. urea, showing there is no need for a special formulation and that commercially available UAN is all we really need as a source. While no nozzle type significantly stood out across all sites the 3-D nozzle did show up a couple times as being statistically better. So the important message would be that while the high tech nozzles could provide some value the traditional flat fan performed quite well. While some differences were seen in droplet size, the lack of consistency leads us to say focus on good coverage with limited drift.
Take-Home Messages
- Foliar N at flowering boosted wheat protein by 12% without affecting yield multiple growing seasons and locations. This increase was from 0.5 to nearly 2.0 % protein.
- Nitrogen source matters – UAN consistently outperformed Aq. Urea.
- Your spray technology mattered but not lot – and 3D nozzles generally gave the best results. The good ole flat fans nozzles still did quite will.
- Match droplet size to your setup – generally fine for UAN and coarse for Aq. Urea.
- This targeted approach enhances grain quality without sacrificing yield, potentially improving grain prices and profitability while using N more efficiently.
- Mother Nature still calls the shots, so keep an eye on the forecast before planning your application. If the weather is hot and dry, this is not a good idea. First, those environments typically result in higher protein anyways. But low humidity will significantly increase the likelihood of burn.
This blog was written based upon the data published in the manuscript “Optimizing Spray Technology and Nitrogen Sources for Wheat Grain Protein Enhancement” which is available for free reading and downloading at https://www.mdpi.com/2077-0472/15/8/812
Any questions or comments feel free to contact me. b.arnall@okstate.edu
Nitrogen and Sulfur in Wheat
Brian Arnall, Precision Nutrient Management Specialist
Samson Abiola, PNM Ph.D. Student.
Nitrogen timing in wheat production is not a new topic on this blog, in-fact its the majority. But not often do we dive into the application of sulfur. And as it is top-dressing season I thought it would be a great opportunity to look at summary of a project I have been running since the fall of 2017 which the team has call the Protein Progression Study. The objective was to evaluate the impact of N and S application timings on winter wheat grain yield and protein. With a goal of looking at the ratio of the N split along with the addition of S and late season N and S, in such a way that we could determine BMP for maximizing grain yield and protein.
My work in the past has shown two things consistently, that spring N is better on the average and S responses have been limited to deep sandy soils in wet years. Way back when (2013) on farm response strips showed high residual N at depth and no response to S. https://osunpk.com/2013/06/28/response-to-npks-strips-across-oklahoma/. But there has been a lot of grain grown since that time expectations are that we should/are seeing an increase in S response. In fact Kansas State is seeing more S response, especially in the well drained soils in east half of the state.
Some KSU Sulfur works.
https://www.ksre.k-state.edu/news/stories/2022/04/video-sulfur-deficiency-in-wheat.html
https://eupdate.agronomy.ksu.edu/article/sulfur-deficiency-in-wheat-364-1
Click to access sulphur-in-kansas-plant-soil-and-fertilizer-considerations_MF2264.pdf
So the Protein Progression Project was established in 2017 and where ever we had space we would drop in the study. So in the end across six seasons we had 13 trials spread over five locations. Site-years varied by location: Chickasha (2018-2022), Lake Carl Blackwell (2018-2023), Ballagh (2020), Perkins (2021), and Caldwell (2021).
First lets just dive into the the N application were we looked at 100% pre vs 50-50 split and 25-75 split (Table 2.) Based upon the wealth of previous work https://osunpk.com/2022/08/26/impact-of-nitrogen-timing-2021-22-version/, its not much of a surprise that split application out preformed preplant and that having the majority applied in-season tended to better grain yields and protein values.
This next table is were things get to be un-expected. While the data below is presented by location, we did run each site year by itself. In no one site year did S statistically, or numerically increase yield. As you can see in Table 2 below, the only statistical response was a negative yield response to S. And you can not ignore the trend that numerically, adding S had consistently lower yields. Even more surprising was the same trend was seen in Protein.
One aspect of Protein Progression trials were that while 0-6″ soil test S tended to be low. We would often find pretty high levels of S when we sampled deeper, especially when there was a clay increase with depth. Sulfur tends to be held by the clay in our subsoil. We are also looking at better understanding the relationship between N and S. In fact a review article published in 2010 discussed that the N and S ratio can negative influence crop production when either one of the elements becomes un-balanced. For example we are seeing more often in corn that when N is over applied we can experience yield loss, unless we apply S. Meaning at 200 lbs of N we make 275 BPA, at 300 N lbs we make 250, but 300 N plus 20 S we can make 275 again. Part of the rationale is that excessive N limits S mineralization. On the flip side if S is applied while N is deficient and yield decrease could be experienced. Maybe that is what we are seeing in this date. Either way, this data is why the Precision Nutrient Management program is spending a fair amount of efforts in understanding the N x S relationship in wheat (which we are looking at milling quality also) and corn.
A quick dive into increasing protein with late N applications. At three of the five location GPC was significantly increased with Late N. In most cases the anthesis (flowering) application was the highest with exception of Caldwell. We will have another blog coming out in a month that digs into anthesis applied N at a much deeper level, looking at source, nozzle and droplet sizes.
Looking at this study in a vacuum we can say that it probably best to split apply your N and that in central and northern Ok the addition of S in rainfed wheat doesn’t offer great ROI. If I look at the whole picture of all my work and experience I would offer this. For grain only wheat, the majority if not all N should be applied in-season sometime between green up and two weeks after hollow stem. I have had positive yield responses to S applied top-dress, but it has always been deep sandy soils and wet seasons. I have not have much is any response to S in heavier soil, especially if there is a clay increase in the two feet of profile. So my general S recommendation is 10 lbs in sandy soils and if you show low soil test S in heavier ground and you are trying to push grain yields, then you could consider the addition of S as a potential insurance. That said, I haven’t seen much proof of it.
Take Homes
* Split application of nitrogen resulted in higher grain yields and protein concentrations when compared to 100% preplant.
* Putting on 75% of the total N in-season tended to result in higher grain yields and protein concentrations when compared to 50-50 split.
* Adding 10 lbs of S topdress did not result in any increase in grain yield or protein.
A big Thanks to the collaborators providing on-farm locations for this project. Ballagh Family Farms, Turek Family Farms and Tyler Knight.
Citation. Jamal, A.,*, Y. Moon, M. Abdin. 2010 Review article. Sulphur -a general overview and interaction with nitrogen. AJCS 4(7):523-529 (2010). ISSN:1835-2707.
Any questions or comments feel free to contact me. b.arnall@okstate.edu
A comparison of four nitrogen sources in No-till Wheat.
Jolee Derrick, Precision Nutrient Management Masters Student.
Brian Arnall, Precision Nutrient Management Specialist.
Nitrogen (N) fertilizer’s ability to be utilized by a production system is reliant upon the surrounding environment. The state of Oklahoma’s diverse climate presents unique challenges for producers aiming to apply fertilizers effectively and mitigate the adverse effects of unfavorable conditions on nitrogen fertilizers. To lessen the effect that unfavorable environments can have on N fertilizers, chemical additions have been introduced to base fertilizers to give the best possible chance at an impact. With that in mind, a study was conducted to investigate the impact of N sources and application timings on winter wheat grain yield and protein, aiming to identify both the agronomic effects of these sources and how variations in their timing may influence the crop. Included below is a figure of where and when the trials were conducted.
In each of the trials, four N sources (Urea, SuperU, UAN, and UAN + Anvol) were analyzed across a range of timings. The sources were categorized on two criteria: application type, distinguishing between dry and liquid sources, and the presence of additives versus non-additives. The two N sources were Urea and UAN. The other products in this study were SuperU and Anvol. SuperU is a N product that has Dicyandiamide (DCD) and N- (n-butyl) thiophosphoric triamide (NBPT) incorporated into a Urea base. Anvol is an additive product which contains NBPT and Duromide and can be incorporated with dry or liquid N sources.
For additional clarification, N- (n-butyl) thiophosphoric triamide is a urease inhibitor which prevents the conversion of urea to ammonia. Duromide is a molecule which is intended to slow the breakdown of NBPT. DCD is a nitrification inhibitor that slows the conversion of ammonium to nitrate.
Urea is a stable molecule which in the presence of moisture is quickly converted to stable ammonium (NH4), however it can be converted to ammonia gas (NH3) by the enzyme urease beforehand. Additionally, when urea is left on the soil surface and not incorporated via tillage or ½ inch of a precipitation event, the NH4 that was created from urea can be converted back to NH3 and gasses off. So, the use of urease inhibitors is implemented to allow more time for incorporation of the urea into the soil.
Ammonium in the soil is quickly converted to nitrate (NO3) by soil microbes when soil temperature is above 50F°. When N is in the NO3 form it is more susceptible to loss through leaching or denitrification. Therefore, nitrification inhibitors are applied to prevent the conversion of NH4 to NO3.
All treatments were applied at the same rate of 60 lbs of N ac-1, which is well below yield goal rate. A lower N rate was chosen to allow the efficacy of the products to express themselves more clearly, rather than a higher rate that may limit the ability to determine differences between product and rate applied. Furthermore, dry N sources were broadcasted by hand across the plots while liquid sources were applied by backpacking utilizing a handheld boom with streamer nozzles. Application timing dates were analyzed by identifying the growing degree days (GDD) associated with each timing which were correlated with the Feekes physiological growth chart displayed in Figure 3. Over the span of the study, N has been applied over six stages of growth. The range of application dates stems from the fact that it is difficult to get across all the ground exactly when you need to.
Over four years this study was replicated 11 times. Of those 11 site years, three did not show a response to N, so they were removed from further analysis. The graph above shows the average yield of each respective source (across all locations and timings). The data shows there is a statistical difference between SuperU and Urea vs. UAN, but no statistical difference between UAN treated Anvol and any other source. The data indicates that on average, a dry source resulted in a higher yield than when a liquid source was applied. This makes sense considering that in many cases, wheat was planted in heavy residue during cropping seasons that experienced prolonged drought conditions. Therefore, it is thought that a liquid source can get tied up in the residue. This was first reported in a previous blog posting, Its dry and nitrogen cost a lot, what now?, and years later, the same trends in new data indicate the same conclusion.
If we look at all timings and site years averaging together there is no statistical difference between a raw N source and its treated counterpart. This result is not surprising as we would expect that not all environments were conducive to loss pathways that the products prevented. Basically, we would not expect a return on investment in every single site year, and therefore you do not see broad sweeping recommendations. There was a 2-bushel difference between UAN and UAN Anvol. As this was a numerical difference, not a statistical one, I would say that while the yield advantage was not substantial there may be economic environments that would suggest general use.
While the evaluation of the four sources across all timings and locations showed some interesting results, this work was performed to see if there was a timing of application which would have a higher probability of a safened N returning better yields. As you look at the chart above it is good to remember the traditional trend for precipitation in Oklahoma, where we tend to start going dry in November and stay dry through mid-January. Rain fall probability and frequency starts to increase around mid-February, but moisture isn’t consistent until March. This project was performed during some of the dryest winters we have seen in Oklahoma. Also, just a note, since the graph above combines all the sites that have differing application dates the absolute yields are a bit deceiving. For example, the Nov and Feb timings include the locations with our highest yields 80+ bpa per acre, while January and February include our lowest. So, the way this data is represented we should not draw conclusions about best time for N app. For that go read the blogs Impact Nitrogen timing 2021-2022 Version and Is there still time for Nitrogen??
Figure 6a and b. A: The mesonet rainfall totals for Oct -Dec for the Lake Carl Blackwell research station for 2020-2023 A: The mesonet rainfall totals for Jan – April for the Lake Carl Blackwell research station for 2021-2024. The black line on both graphs is the 10 year average.
Now about the source by time. While it’s not always statistical you can see that the dry sources tend to outperform the liquid sources at most timings. Also, while there is never a statistical difference in the raw product and safened, there are trends. SuperU tended to have higher yields than urea when applied in Nov and Dec. It could be hypothesized that the addition of a nitrification inhibitor may have added value, however the UAN + Anvol in November also showed a positive response that would point to the value being derived from urease inhibition. As we move into the period of more consistent rainfall the differences between products start declining, which also makes sense.
The following figures illustrate rainfall events following N application, with the application dates indicated by arrows. Figure 7 corresponds to our trial conducted in 2020-2021, which revealed no statistical differences among the N sources for any timing. However you can see that for the first timing (orange bars) which received 0.7″ of rain two days after application that the yields are uniform than the grey bars with both safened products are numerically greater than the raw product, just makes since as a 0.1″ precipitation event happened 6 days application application and it wasn’t until day 9 that a good incorporating rainfall occurred.
Figure 8 has data the same location one year later, during which we observed statistically significant differences among the dry and liquid N sources. The environmental conditions during 2022 were drier, impacting the incorporation of N applications. The lack incorporating rainfall likely led to tie-up of the UAN on/in the residue, limiting access to plant available N.
It is essential to highlight the environmental conditions encountered throughout this project. From 2020 to 2023, moderate to extreme drought conditions were prevalent. During this period, the influence of a La Niña led to reduced moisture availability. For the first time in an extended period, the 2023-2024 wheat year began under a strong El Niño, which typically results in increased moisture accumulation compared to its La Niña counterpart. Currently, there are indications that a return to a La Niña system may occur by the end of the year, raising the expectation of a potential reversion to drought conditions. Consequently, this research may provide producers with options to consider regarding sources of N application in their production systems.
We plan to update this blog with a deeper analysis of the results seen at each location as soon as possible. But for now, we wanted to share the early look.
At this point the reason for the liquid yield gap is speculation. It could be increased loss via ammonia volatilization or it could be immobilization of the N by microbes. The next step of this process is to understand 1) is the UAN tied up in the residue via immobilization via microbes or is it lost to volatilization. 2) If tied up, what is the time frame between application and immobilization.
Take Home:
- It was observed that during low moisture conditions, dry N sources had significantly better results than liquid counterparts in no-till winter wheat production.
- On average, additive products had no significant impact on grain yield versus base fertilizers, however, when evaluated by location, differences could be found. Responses usually correlated with post-application weather conditions.
- When adequate precipitation was received shortly after application, N sources did not show differences.
Any questions or comments feel free to contact me. b.arnall@okstate.edu
Down and Dirty with NPK 