Sulfur

Late-Season Soybean Moves That Can Swing Yields By Up To 15 Bushels

Fri, 14 Aug 2026 16:25:19 GMT

While another round of weather extremes is bearing down on soybean fields as mid-August gets underway, growers still have opportunities to protect 2026 yield potential, according to Missy Bauer.

Bauer, Farm Journal Field Agronomist and co-owner of B & M Crop Consulting in Coldwater, Mich., says the focus now should be on the soybean yield components growers can still influence: number of seeds per pod and seed weight.

“If I’m really trying to push my soybean yields, I need to think about these yield components,” Bauer told AgriTalk host Chip Flory on Thursday.

Soybean yield is developed based on these components:

Number of pods per plant
Number of beans per pod
Seed size or weight

At this point in the season, pod number is largely established — primarily because genetics plays a major role. But management and growing conditions can still influence seed development and final seed size.

Seed Size Could Be The Swing Factor This Season

Bauer says seed size deserves particular attention because it can make a major difference in final yield.

“That seed size all of a sudden can swing bean yields 15 bushels one way or the other,” she says.

In her area, south-central Michigan, Bauer says farmers have experienced three consecutive falls with difficult seed-fill conditions that ultimately reduced yields.

Heavy rain raises concerns about Sulfur Availability

Too much rainfall across some eastern Corn Belt states this month is creating another late-season concern: nutrient loss, particularly sulfur.

“Sulfur is a big deal when we go to fill out these seeds, making sure we have enough nutrition in that plant to fill what we have,” she says.

Sulfur is mobile in the soil and can leach below the root zone during excessive rainfall, with the risk particularly high on sandy soils.

While Bauer emphasizes that late-season soybean management isn’t about relying on a single input or practice, growers still have several opportunities to protect seed fill and final yield potential.

Here are six late-season soybean considerations for farmers to evaluate:

1. Determine whether sulfur is actually needed

A late-season sulfur application might help, but only when a genuine deficiency exists.

Purdue Extension research indicates foliar sulfate-S has corrected in-season soybean sulfur deficiencies at V4, R3 and R5. In those trials, about 3 lb. of SO₄-S per acre performed best. An R5 application may have value when a deficiency is confirmed, while higher rates caused leaf burn.

2. Protect the upper canopy from foliar disease

Keep scouting for diseases that can reduce green leaf area during seed fill. Foliar fungicides can reduce diseases such as frogeye leaf spot when applied at later reproductive stages. However, treatment decisions should be based on disease risk, variety susceptibility and local recommendations, advises the Crop Protection Network.

3. Keep scouting for insects

Soybean aphids and other pests deserve attention, particularly during R5 and into early R6. Extension recommendations call for continued soybean aphid scouting through these stages, although the potential for yield loss declines as the crop approaches full seed.

4. Look for pod and stem diseases

Pod and stem blight, for example, can cause infected seeds to crack, shrivel and become moldy. Oklahoma State University Extension reports that foliar fungicide applications during R5-R6 can improve seed quality from pod and stem blight in years characterized by warm weather and frequent rainfall.

5. Don’t spray foliar fertilizer just to keep soybeans green

Late-season foliar nutrition has sometimes been promoted as a way to delay senescence and improve seed size. But research does not consistently support that strategy.

Iowa State University reports numerous trials have produced inconsistent results, including some yield decreases. More recent research indicates a low probability of a yield increase from late-season foliar fertilization.

Bauer To Address Soybeans at Yield Academy

Bauer will expand on these themes at the Farm Journal Yield Academy in Rochester, Minn., next week during the final day of the 2026 Pro Farmer Crop Tour.

She will walk growers through a systems approach to soybean yield components and discuss where late-season management can make the biggest contribution.

Growers can learn more about the program and register at farmjournalyieldacademy.com . When prompted for a coupon code, AgriTalk’s Chip Flory adds that growers can enter “agri” for an available discount.

Do Soybeans Need Sulfur? Illinois Trials Point to When It Pays

Thu, 13 Aug 2026 21:57:21 GMT

When Illinois Soybean Association (ISA) Outreach Agronomist Stephanie Porter launched the group’s first on-farm sulfur (S) trial network, she wanted to answer a question farmers across the state were asking:

If I’m already applying sulfur to corn, do my soybeans need it, too?

After a season of trial work across Illinois in 2025, the answer is sometimes — but only under certain conditions. Porter addressed the research during the 2026 Field Advisor Forum .

What the ISA Trials Found

ISA used fairly large plots to conduct the research rather than small research strips. Each trial had:

At least 40 acres
Four replications of a sulfur treatment and four untreated strips
Strips at least 60 feet wide, or twice the width of the combine head
A target sulfur rate of 30 lb. S/acre, spring applied

Porter says the 30-lb. rate was intentionally high for research purposes. It was designed to give sulfur every opportunity to produce a response, not to establish a farmer recommendation.

Growers used ATS or AMS, with some gypsum included in the broader research effort.

“[ATS] is easier, like kind of a liquid product for them to apply. The one key thing I want you to note about that is that ATS is half sulfate, half elemental sulfur. So that sulfate is the readily available form for that plant to take up, but you still have the elemental sulfur that’s not readily available,” Porter says.

The Illinois research team collected soil and tissue samples, plant measurements, yield data and five years of historical field-management history. All protocols can be found on FieldAdvisor.org.

Only Four Fields Showed a Clear Yield Response

Across the statewide trials, only four fields had a clear yield response to sulfur. One other field had a numerical increase that was not statistically significant.

The responsive fields did not all look alike. However, Porter says several common factors stood out.

One Bureau County field produced a 7.4-bu./acre increase even though the grower applied only about half the planned rate — roughly 15 lb. S/acre.

That field had relatively sandy soil, about 3% organic matter and medium CEC. Those conditions can increase the chance of sulfur loss through leaching and may limit the amount of sulfur supplied by organic matter, Porter notes.

Other responsive fields had more organic matter — around 4.5% — but were still relatively sandy.

The lesson is important: no single soil characteristic predicted a sulfur response. Soil texture, organic matter, CEC and field history all played a role.

Start With the Soil

Porter recommends farmers evaluate their soils before considering the fertilizer product.

Sandy soils are more likely to lose sulfate through leaching, which can increase the chance of a sulfur response.

Organic matter also supplies sulfur. As a general estimate, each percentage point of organic matter can mineralize roughly 3 lb. to 5 lb. of sulfur per year. Fields with less organic matter may have less sulfur available to the crop.

CEC and soil type can provide additional clues. Higher-CEC soils often have more organic matter and a greater ability to supply sulfur. But some higher-CEC fields still responded in the trials.

A key point is that some Illinois soils can supply enough sulfur on their own. Applying sulfur without considering that supply can add cost without adding yield, Porter says.

Management Matters, Too

Soil quality was only part of the story. Field management also helped explain the differences in response among sites.

Early planting:
Early-planted soybeans came up repeatedly in the discussions about sulfur. Porter says the trial results support the idea that early-planted soybeans may be more likely to benefit from sulfur, but early planting alone does not guarantee a response.

Residue and tillage:
Several responsive fields had heavy residue, including no-till and fall-till fields with substantial corn residue remaining on the soil surface.

Residue can temporarily tie up nutrients as microbes break it down. The carbon-to-nitrogen ratio of the residue affects this process, and sulfur can also be involved, Porter explains.

She adds that one particularly interesting Knox County field compared AMS and ATS. The AMS treatment produced the better response. One possible reason is that AMS supplies sulfur entirely as sulfate, making it almost immediately available.

Cover Crops May Change the Picture

The use of cover crops was another interesting part of the 2025 trials.

One strong sulfur response occurred in a plot where cover crops had been grown. That fits with some university research in Illinois and Indiana showing greater potential for sulfur response in fields with cover crops, Porter says.

Cover crops do more than tie up nutrients. They can capture and hold nutrients such as sulfur, potentially changing when that sulfur becomes available to the next crop.

Porter says that raises an important question: Are cover crops helping keep sulfur in the system, or are they delaying its availability to soybeans?

Previous Sulfur Applications Matter

One of the clearest differences between responsive and non-responsive fields came from the five-year management histories collected by Porter and her colleague Darby Danzl, a regional technical agronomist for the Illinois Soybean Association .

The team rated previous sulfur use from none to very high. Fields that responded in 2025 generally had no or very little sulfur applied in 2024.

Many fields that did not respond had received sulfur regularly, usually as part of their corn fertility program.

That suggests soybean sulfur decisions should not be made one year at a time.

If sulfur has been applied regularly to corn, soybeans may already be benefiting from that fertility. This is one reason farmers should take their whole rotation into consideration, and not just the current soybean crop, notes Porter.

Soil and Tissue Tests Can Help

Soil sulfur tests are useful, but Porter cautions that they are only snapshots of what is happening in the field.

Two responsive sites in Champaign and Vermilion counties, east-central Illinois, had relatively low spring soil sulfur levels—24 ppm or less on the scale used in the trials. At R1 to R2, tissue tests also showed higher sulfur concentrations in the treated strips.

The opposite occurred in a Menard County, Ill., field. It had the highest soil sulfur test in the trial, at about 31 ppm. Sulfur treatment did not produce a meaningful difference in tissue sulfur or yield.

Porter’s perspective is soil and tissue tests can help identify fields that may be short on sulfur, but neither test should be used as the only reason to apply it.

Don’t Chase Yield With 30 Pounds of Sulfur

The 30-lb. rate used in the ISA trials was for research — not a recommendation.

“I do not want you to go out and apply 30 pounds of sulfur; that is not economical,” Porter told farmers.

Danzl’s economic analysis of the roughly 2.5-bu./acre response in Vermilion County shows why.

At an ATS price of $320/ton, the treatment barely broke even. At a more typical $400/ton price from 2024, it would have lost money.

For fields where soil, management and field history suggest a possible sulfur shortage, Porter said between 15 and 20 lb. S/acre is a
more realistic rate to consider.

What Farmers Should Watch For

The 2025 trials reinforced what Porter would tell farmers to keep in mind: Sulfur should not be used as a blanket application for soybeans.

Instead, in trying to decide where sulfur use would make financial sense, she says to look for fields where a portion or all of these eight risk factors come together:

Sandy or relatively coarse-textured soil
Lower organic matter
Heavy corn residue
No-till or other systems with substantial surface residue
Cover crops
Early planting
Little or no recent sulfur application
Low soil sulfur test results

Yellow Corn, Delayed Soybeans and the Summer of Hard Choices

Fri, 10 Jul 2026 16:40:01 GMT

In a season marked by uneven corn development and delayed soybeans, Farm Journal Field Agronomist Ken Ferrie is telling growers to lean on in-season management rather than write fields off.

“Don’t walk away from a growing crop. Stay the course,” encourages Ferrie, who’s based in central Illinois.

Speaking on his latest Boots In The Field report, Ferrie lays out five priorities for farmers’ consideration now.

1. Diagnose what’s causing “yellow” corn: sulfur vs. nitrogen deficiency.

Ferrie says most cornfields in his area are progressing well, but ponded areas are concerning. He is telling farmers to make an accurate diagnosis what the problem is before applying additional nutrients.

Yellow on the upper leaves with green tissue below points to a sulfur deficiency, while pale plants from top to bottom with lower leaf cannibalization down the midrib signal a nitrogen deficiency. Some fields of corn show both.

“Adding nitrogen to a sulfur deficiency won’t fix that problem,” Ferrie says, urging growers to use plant photos and quick nitrate tests to sort out the issue.

He adds that some ponded corn crops are so stunted they are “not worth saving,” but others still have yield on the table if fertility needs and stress are addressed now.

2. Consider using ponded and replant areas as a chance to pivot.

With “a large amount of double-crop beans” going in behind wheat, soybeans and even corn, Ferrie wants farmers to be proactive in addressing ponded out areas.

“If possible, I recommend planting something in these ponds to help manage the weeds and rebuild the soil biology after being drowned out,” he says.

Where ponded areas in the middle of fields are inaccessible without damaging a good crop, Ferrie advises seeding covers by drone.

Soybeans, he notes, are rebounding much more slowly than corn after saturated soils because growers must “rebuild the soil biology, especially Rhizobia, then the root system, then the nodules.” Even so, he expects visible improvement in many ponded areas within the next week, especially if weeds are controlled.

3. Reassess rootworm strategy: “catch crop” risk is real.

Ferrie reports substantial rootworm feeding in central Illinois cornfields, including in fields planted with traited hybrids. He and his team are finding four to seven larvae per plant and as many as two full nodes of roots missing, especially in fields north of Bloomington.

“When you find this feeding, one thing is clear: your current insecticide plan is not working, whether that’s crop rotation or traits,” he says.

“If you sprayed twice last year to control southern rust and tar spot and had some of the greenest corn in the neighborhood, your green crop became the neighborhood catch crop for corn rootworm,” he adds.

What transpired is fungicide programs kept the corn crop green in some areas. Both northern and western rootworm beetles concentrated in that green corn to feed and lay eggs, setting farmers up for higher rootworm pressure this year.

Ferrie cautions growers who want to drop traits or insecticide “to save money on rotated acres” without hard scouting data. Sticky traps in beans alone can be misleading when beetles concentrate in greener corn.

“Pest teams paying attention to sticky traps in both crops in late August and doing root inspections, looking for feeding, are all good tools to help us make the call on what we can do to cheapen up our rootworm control,” he notes.

4. Treat pollination as “go time” for insect scouting.

With April-planted corn in central Illinois currently pollinating and May corn 10 days to two weeks out, Ferrie calls this “go time for all pest teams.” He wants close scouting for silk-clipping insects.

Uneven stands, water damage and replanted fields create extended pollination windows that allow beetles to migrate from plant to plant and from main fields into replanted areas.

“The more strung out the pollination, the more trouble we have,” Ferrie says, warning that many growers replant ponded acres but “forget to watch the silk clipping and end up with poor pollination.”

He adds that drones can be a practical tool to treat isolated ponded areas at their later pollination timing without damaging surrounding crops.

5. Delay fungicide unless current disease pressure demands it.

Tar spot, northern leaf blight and weather-related issues like physoderma brown spot are already showing up, but Ferrie does not want growers pulling the fungicide trigger early in otherwise healthy fields — especially while pollination is still uneven.

“Without heavy disease pressure, I would monitor pollination to be sure we don’t have to deal with the beetles or the aphids to get this crop pollinated,” he says.

Spraying too early, he warns, can create extra trips.

“Jumping the gun too soon with your fungicide could cause you to have to go back and clean up the insects,” Ferrie says. “Many of these fields will pollinate uneven due to water damage, so wait for the ponds to get pollinated before you pull the trigger.”

Ferrie wants pest teams to keep monitoring disease pressure as weather evolves, but to give priority to securing clean, complete pollination before layering on fungicide where pressure is still relatively light.

You can hear more of Ferrie’s in-season agronomic recommendations in his latest Boots In The Field podcast at the link below. Be sure to hear the details on the upcoming Farm Journal Corn & Soybean College July 21-22 at the Crop-Tech Consulting campus in Heyworth, Ill. The event features two days of unsponsored, in-depth agronomy — classroom sessions plus hands-on field time. You can learn more and sign up here .

Strait Of Hormuz Is Open: What It Means For Fertilizer

Thu, 25 Jun 2026 22:35:13 GMT

As of today, 70% of the sulfur tons that were trapped behind the Strait of Hormuz due to its closure have now transited through and are in transit for the global market.

That was the good news shared by The Fertilizer Institute’s Corey Rosenbusch on AgriTalk. Fertilizer is once again flowing through the critical part of the global supply, which had been largely blocked for traffic since the end of February. Every year more than one-third of all fertilizer globally transits through the Strait of Hormuz.

“Half of the world’s sulfur that’s traded comes through the strait,” he says. “Because it’s the key raw material in phosphate production– Saudi phosphate, Moroccan phosphate, US phosphate–they had all started to curtail production because they couldn’t get sulfuric acid to make it.”

Rosenbusch says urea vessels are also starting to flow again, “moving in the right direction,” but he’s hesitant to give exact estimates on how delayed or damaged the global supply chain is beyond being “months to years” for full recovery.

With uncertain timeline for full recovery, the industry is watching for updates on any manufacturing or infrastructure damages in the production of fertilizer in the region that could have occurred during the conflict so far.

What Does This Mean For Prices?

Volumes moving doesn’t necessarily equate to supply level increases. Or immediate price relief.

“Most of those tons, including a lot of the urea tons, we believe are already committed tons, so it’s not going to necessarily add a lot of supply right now, but it is still good news to get those tons moving,” he says.

Emphasizing the complexity of global fertilizer markets, Rosenbusch points to the seasonal nature of pricing as well as government interventions adding to the dynamics.

“A big driver of them (markets) is the seasonality of application, and so once we got through the season, as we do every season, you start to see those markets shift, and that’s what did happen in the context of so those prices could come down to pre-conflict levels,” he says.

He says India is a global price-setter because of its government intervention, and that country was sourcing about half of its urea this spring via supplies through the Strait of Hormuz.

“What a farmer in Iowa is going to pay is what the government of India is willing to subsidize for their farmers, and so if they’re going to pay $900 a ton for urea because they just give it to their farmers as part of their social program then we’re subject to competing for those tons on a global marketplace,” he says.

Building Resilience: Why U.S. Production Matters Now

While the Strait of Hormuz is critical for global fertilizer trade flows, domestic production has been taking focus.

Regarding the Trump administration’s efforts to increase domestic production of key fertilizer productions, Rosenbusch says the industry appreciates the recognition of its value for the country. The recognition is being paired with realistic timelines and investment requirements to develop more production. The administration is focused on building resiliency in supply and lowering input costs for farmers.

“We met with four cabinet secretaries talking about how to bolster domestic production, and the question was asked, ‘Can we get these new plants online in 12 to 24 months?’ And the answer is, it could take five years to build a nitrogen plant, and $4 billion or $5 billion.”

Rosenbusch says it was recognized how the industry is complex, and TFI members want to have conversations about how to add to the industry but not overtake the industry.

“We don’t want to see our plants owned and operated by the federal government,” he says. “I’m not sure growers would appreciate the federal government owning and operating these plants. We’re a free enterprise economy, markets work, we have to let them work. I don’t think we want to be a socialist fertilizer industry.”

Could More International Sources Come To Market?

“In the middle of all this, China decided to reenter the market, so they made an announcement a few weeks ago that they were going to allow urea exports again. We had heard that their production had outpaced the previous year by about 20% yet they still kept their export bans in place,” he says. “China is the world’s largest producer of fertilizer. They have historically opened their exports when Brazil gets to planting season, but they went a little early this year, and I think that’s why you saw a lot of the urea market move as well.”

Corn Nutrient Decisions Hit Crunch Time By V8

Mon, 22 Jun 2026 17:35:55 GMT

Farmers across the Corn Belt may be tempted to park their sprayers and hope for the best after a wet spring and record-high input bills. But Farm Journal Field Agronomist Missy Bauer warns that could be the costliest decision they make when it comes to their corn crop.

A mix of too much moisture along with stints of warm soil temperatures this spring opened the door to denitrification and leaching, Bauer notes. For those reasons, she believes corn growers can’t assume their original nutrient plan is still working.

“Maybe you had a great May and first half of June,” she says. “I think you still need to be probably pulling some nitrate samples to make sure that you’re not going to leave anything on the table with this crop.”

Nitrate Tests Require A Different Approach

For growers who decide to test, Bauer stresses that a soil nitrate sample is not the same as a routine soil fertility test. Depth of testing matters.

Standard soil samples usually go 6 to 7 inches deep. Bauer wants farmers to double that — and, where possible, to look even deeper.

“We want to go down into the soil and pull at least a full foot,” she says. “If you’re in an area that you could go back down the same hole and get the second foot of soil to test that would be ideal.”

Sampling the first and second foot can help determine whether N has simply moved lower or is largely gone.

“If it’s in that second foot, we’ll have opportunities to pick that up in the corn crop later in the season,” she says. “But if both feet are flushed, then we know we’re in real trouble.”

At the same time, Bauer acknowledges that high N prices have many farmers looking for places to cut costs. She urges diligence.

“Maybe you can cheat on phosphorus, or you can cheat a little on K, but you can’t cheat on nitrogen,” she says. “The crop needs a lot of nitrogen to push yield and push those bushels.”

She advises any grower who trims N rates to back up that decision with in-season nitrate tests and tissue samples, including around tassel, and to be prepared to respond quickly if numbers come in short.

Rapid Growth Stages Are Underway

Timing and N availability become even more critical as corn hits rapid growth stages, which is starting to occur across much of the Midwest.

“The bulk of your nitrogen — I’m not saying all of it — the bulk needs to be on by the time we get to about V8 to V9,” Bauer says, noting that from that stage to tassel, corn can take up 7 to 8 pounds of N per acre per day.

Banded applications — whether with coulter injection on smaller corn or via Y-drops — can help stretch N dollars, she says, particularly if the weather turns dry after decisions are made.

“We can be super successful with [Y-drop] even if it turns dry,” she says, because the band sits “real close to the base of the plant.”

Keep Sulfur Available, Too

Nitrogen isn’t the only nutrient Bauer worries about this season. With little sulfur (S) now coming from atmospheric deposition, she says wet weather and skipped preplant applications are combining to expose deficiencies.

“Sulfur is definitely a potential issue this year with the rains that we’ve had,” she says, adding that many growers dropped ammonium sulfate ahead of planting to save money and then “were just adding the extra N later.”

Rather than across-the-board cuts, Bauer encourages farmers to use variable-rate nitrogen to “move around nitrogen dollars,” pulling back on high-organic-matter low ground and feeding lighter, yield-limited hills.

Above all, she says, this is not the year to manage your corn crop from the road.

“Don’t walk away from your crop,” Bauer says. “Get out in your fields, do some evaluations of your crop so we know what we have to protect as we go through this season.”

4 Agronomic Pillars Every Corn Grower Needs

Mon, 13 Apr 2026 18:50:44 GMT

What if the next 10-bushel bump on your corn ground doesn’t come from a new product or technology but from how deep you set the planter and where you placed nitrogen? Dan Quinn, Purdue University corn specialist, says the biggest yield gains still come from decisions that sound simple on paper and are hard to execute in the field.

For Quinn, a winning season hinges on four pillars: plant deep enough for consistent moisture, protect uniform emergence and roots, respect nutrient interactions, and use technology and timing to manage risk — not to shortcut agronomy.

“Fundamentals are fundamentals for a reason,” Quinn says. “If something’s off… you’re not going to get any benefit from some of those more progressive practices.”

Here are the four recommendations he offers growers to get a strong start this season:

1. Consider Moisture Availability, Not Just Planting Depth

A successful season begins at the planter, but Quinn warns against getting comfortable with a “standard” depth. He argues that corn should be placed where moisture access is reliable, even if that means pushing seeds deeper than your traditional comfort zone.

“I’d rather be a bit on the deeper side than the shallow side,” Quinn says. “We’ve done some seed depth work showing corn can get out of the ground at 4 inches deep.”

While his typical target is a 2-inch depth, he advises growers to move deeper in dry conditions. The primary goal, he advises, is to ensure every seed sits in the same soil and moisture conditions to trigger uniform germination.

To complete the imbibition (water uptake) phase of germination, corn needs to absorb 35% of its weight in moisture, according to University of Nebraska Extension research . When adequate soil moisture is available, this typically occurs within 48 hours.

2. Protect Uniform Emergence And Early Root Growth

Quinn calls corn “a pain” because it offers little to no forgiveness when emergence is uneven.

“We have to get it out of the ground at the same time,” he says. “It has to be uniform, it has to get out of the ground quickly, and it has to get that root system established and moving.”

When a field looks off, Quinn said that nine times out of 10, the problem can be identified below the surface. Issues like fertilizer salt injury, compaction, or heat desiccation in sandy soils often start early but don’t manifest visually until weeks later.

“We see more often than not that if you have problems… a lot of times you can point back to that root system,” he says.

3. Master The N:S Ratio And Starter ROI

As yield targets climb, the conversation is shifting from “how much nitrogen” to “how does nitrogen interact with other nutrients.”

Quinn is specifically watching the relationship between nitrogen (N) and sulfur (S).

“Nitrogen and sulfur behave very similarly in the plant. They’re kind of joined at the hip,” he says.

Purdue research shows that high nitrogen rates can actually induce sulfur deficiency by throwing off the plant’s internal balance. As you push N rates and yield potential up, the crop’s sulfur demand also increases. If S isn’t increased proportionally, sulfur can become a limiting nutrient in the system. Quinn currently recommends 15 to 25 pounds of sulfur per acre, though he believes that might be a bit low in a high-yield system.

Additionally, Quinn remains a staunch advocate for starter fertilizer. Beyond the agronomic “safety net” it provides as corn transitions off seed reserves, he points to a secondary economic benefit: lower grain moisture at harvest.

“I’ve seen trials where just the drying savings from starter is enough to pay for the system, even beyond the yield benefit,” he says.

4. Use Tech As A Guardrail, Not A Crutch

While Quinn supports the use of variable-rate planting and advanced sensors, he views them as tools to manage risk rather than replacements for boots-on-the-ground agronomy.

He highlights hydraulic independent downforce as a game-changer for maintaining consistency in variable soils. However, he notes that even the best technology cannot fix a poor timing decision. In Indiana, this has led to increased reliance on sidedress nitrogen to limit exposure to unpredictable spring weather.

“It helps reduce some of the risk and vulnerability,” Quinn says. “It’s about making sure we do what we can to maintain having that nutrient available for the plant when it needs it most.”

Hear more of Quinn’s insights and recommendations on this episode of A Penney For Your Thoughts Podcast

Solving The Sulfur Shortage In High-Yield Soybean Systems

Mon, 16 Mar 2026 16:45:27 GMT

As more farmers push to plant soybeans early, one nutrient is emerging as a valuable difference-maker in the crop: sulfur. The macronutrient is helping deliver some of the largest yield responses Shaun Casteel says he has seen in recent field trials.

“Never would you think you’d see double-digit results, let alone 20-bushel numbers in soybean yield from one treatment,” says Casteel, Purdue University agronomist and Extension soybean specialist.

Yet that’s exactly what he has documented in some Indiana fields where supplemental sulfur was applied, especially in early planted soybean fields.

Why Sulfur Matters More Now

Sulfur is required by all crops, but Casteel says soybean needs are unique compared with grass crops like corn. In soybeans, sulfur is critical as a co-factor for nodulation, the biological process that allows soybean plants to use atmospheric nitrogen (N).

“If we don’t have good sulfur supply, we don’t have good nodulation and fixation,” Casteel explains. “If you’re sold short on nitrogen in soybeans, you’re sold short on yield in a major way.”

Historically, sulfur came “free” from the atmosphere and also from mineralization of organic matter in the soil. Cleaner air regulations have reduced atmospheric deposition, and Casteel says many farmers are starting to see sulfur shortages that weren’t obvious just as recently as a decade ago.

Historically, sulfur was readily available to soybeans via atmospheric deposition (acid rain) from industrial emissions, providing 10 to 30 lbs./acre annually. Due to the 1970 Clean Air Act reducing emissions by over 95%, this “free” source has disappeared, making sulfur supplementation essential to prevent deficiencies, especially on sandy soils, according to University Extension.

(Shaun Casteel)

The classic high-response situations for sulfur — coarse-textured, sandy soils with less than 2% organic matter — still stand out. But Casteel’s work is showing the story for sulfur doesn’t end there.

“I also have fields that are flat and black as a table, with 4% organic matter, where we’re getting sizable yield differences,” he says.

Early Planting Amplifies Sulfur Response

Casteel links some of the most dramatic sulfur responses to a broader trend across the country: earlier soybean planting.

In Indiana, planting patterns have shifted sharply in recent years. Soybeans that once went in the ground two weeks after corn are now being planted within a day or two of corn — and in many cases, are planted first.

Early planting improves yield potential by giving soybeans more time to develop nodes and reproductive branches. But it can also expose a weakness in the natural sulfur supply.

For those farmers chasing higher yielding soybeans, Shaun Casteel believes the use of supplemental sulfur deserves more consideration.

(Shaun Casteel)

Casteel points out that mineralization of sulfur from soil organic matter depends on microbial activity and warm temperatures. When soybeans are planted in late April or early May, Indiana soils – as week as soils in other states – are often too cool for the microbes to release much sulfur.

“In those cooler conditions, that mineralization really isn’t occurring,” he says.

Across multiple studies where planting date was combined with sulfur use, Casteel has seen consistently stronger responses in early-planted soybeans.

“We’ve got years that we’re averaging an 8- to 11-bushel response on prairie soil,” he says. In these trials, sulfur was (e.g., ammonium sulfate, pelletized gypsum, ammonium thiosulfate) applied pre at 20 pounds per acre during a 5-year period.

Beyond Fertility: A Surprising Disease Connection

Sulfur’s role may extend beyond delivering nutrition and helping fix nitrogen in soybeans. Casteel and his research team are seeing signs that sulfur helps reduce the severity of sudden death syndrome (SDS) in soybeans.

In a 2023 soybean trial, as Casteel began rating symptoms of SDS, he noticed a clear difference between sulfur-treated and untreated strips.

“We had good conditions for SDS development — cool, wet conditions during early vegetative growth. We had a marked, substantial reduction in SDS in those areas that had the sulfur treatment,” he recalls.

The unexpected result prompted a deeper look in 2024, when Casteel worked with Plant Pathologist Darcy Telenko on trials that combined planting dates, sulfur rates and SDS inoculation. Early data from those studies pointed in the same direction: soybeans receiving sulfur showed reduced disease expression.

“Beyond the fertility effect, beyond the fixation-boosting capacity that comes with this, there is evidence that we have some disease control or suppression,” Casteel says, cautioning that the results are still based on only a few years of data.

“If you really think about it, the first fungicides on the market 100 years ago were sulfur-based, so it’s not too surprising that we might be seeing something here,” he adds.

Big Upsides Where Sulfur Use Fills The Gap

Casteel is careful to note that the sulfur response in soybeans is often site-specific. Classic sandy soils and low-organic-matter fields are prime candidates for the nutrient. But his work suggests that even high-organic-matter fields can show strong gains when sulfur is limiting.

(Shaun Casteel)

That variability doesn’t dampen his enthusiasm. Instead, he sees sulfur as a high-upside tool for intensive soybean managers who already have the basics — variety selection, disease packages, and timely planting — under control.

“It’s fun to have treatments out there that are providing hope and promise,” Casteel says. “We’re seeing numbers with sulfur that really move the needle.”

With earlier planting becoming the norm and biological sulfur supply under pressure, Casteel expects interest in using Sulfur to keep growing. For those growers chasing 100-bushel soybeans, especially, he believes sulfur deserves more consideration as they develop fertility plans.

“If you have not explored sulfur on your soybean crops, I suggest applying strips of S fertilizer that is soluble (e.g., ammonium sulfate, pelletized gypsum, ammonium thiosulfate) between 15- to 25-pounds of S per acre to determine if you have fields or production practices that are responsive to boosting nodulation and N fixation,” he recommends. “Applications can be applied mid-March through planting with higher rates the earlier you apply the S fertilizer.”

More information on Casteel’s research with sulfur in soybeans is available here .

Dynamic Duo: Research Shows 2-For-1 Benefit Pairing Ammonium Thiosulfate With UAN

Tue, 01 Jul 2025 15:33:25 GMT

Since 2017, Dr. Zack Ogles, manager of agronomy, at Tessenderlo Kerley, has been trying to understand how applications of thiosulfate can inhibit nitrification when applied with a UAN.

In other words, by adding thiosulfate, increasing the sulfur rate slightly or making a slightly different application method, could one fertilizer benefit the other? Could 1 plus 1 equal 3?

Ogles says yes, as well as a recently published paper in the Soil Science Society of America Journal, which recaps the test results. Thiosulfates not only supply sulfur but also significantly reduce nitrogen loss by slowing the conversion of ammonium to nitrate in the soil.

“We’re improving outcomes on multiple levels,” Ogles says. “By delivering both sulfur and nitrogen protection in a single application, these products help growers maximize return on investment while advancing sustainable farming practices.”

The light bulb moment.

Ammonium thiosulfate (ATS and sold under the brand Thio-Sul) and potassium thiosulfate (KTS) are used in liquid formulations, and typically, ATS is applied in a blend with urea ammonium nitrate (UAN) for a 28-0-0-5(S) fertilizer analysis.

Ogles says prior to the confirmation provided by the laboratory study as well as in-field research, agronomists had recognized the potential for thiosulfate to provide a similar benefit as Dicyandiamide (DCD), a commonly used nitrogen stabilizer.

“Both Thio-Sul and KTS were shown to inhibit nitrification comparable to DCD, in the three soils used in the published research. Additional studies are needed to fully understand how thiosulfates perform in a broader range of soil types and conditions,” he says. “Prior to this research, thiosulfates were often regarded as weaker nitrification inhibitors and with limited effect. But what we discovered in this study was that at the rate thiosulfates are being applied today, we’re seeing effects equal to, or even greater than commercially available nitrification inhibitors.”

Ogles says with the increased focused of sulfur as the “fourth major nutrient,” and most crops requiring sulfur fertility, a banded/concentrated application of thiosulfate applied at the time of planting brings a new agronomic opportunity.

“The big advantage is that you can use a fertilizer to help improve the efficiency of nitrogen,” he says. “In other words, using a thiosulfate fertilizer with these enhanced properties helps improve the effectiveness of the nitrogen that’s being applied.”

The laboratory trials explained in the recently published paper include studies across soil different soil types, which were brought in from California, Iowa and Alabama– Marvyn loamy sand, Tujunga loamy sand, and Sable silt loam.

The trial applied urea solution along with between 15 and 30 pounds of sulfur in the form of ammonium thiosulfate or potassium thiosulfate.

Results

“It allows more of the nitrogen to remain in the ammonium form which is stable in the soil, and it’s not a subject to denitrification,” Ogles says.

This was backed up by a separate field trial conducted over seven site years, which showed an 8 to 10 bu. increase in corn yield.

Ogles says because nutrient use efficiency is driven by soil types and environmental factors more research will continue to be done across various geographies and soil types.

“We are proud to say these thiosulfate fertilizers are important on multiple levels. They provide the sulfur nutrition which crops already need, while helping improve nitrogen use efficiency and maximize yield, all while protecting the environment from leaching and denitrification,” Ogles says.

The full scientific publication authored by Lane A. Galloway, Audrey V. Gamble, Elizabeth A. Guertal, Yucheng Feng, and C. Z. Ogles is available here. Potential of ammonium thiosulfate and potassium thiosulfate to inhibit nitrification in soils - Galloway - 2025 - Soil Science Society of America Journal - Wiley Online Library

Sulfur

Late-Season Soybean Moves That Can Swing Yields By Up To 15 Bushels

Seed Size Could Be The Swing Factor This Season

Heavy rain raises concerns about Sulfur Availability

1. Determine whether sulfur is actually needed

2. Protect the upper canopy from foliar disease

3. Keep scouting for insects

4. Look for pod and stem diseases

5. Don’t spray foliar fertilizer just to keep soybeans green

Bauer To Address Soybeans at Yield Academy

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What the ISA Trials Found

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Start With the Soil

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Cover Crops May Change the Picture

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Soil and Tissue Tests Can Help

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1. Diagnose what’s causing “yellow” corn: sulfur vs. nitrogen deficiency.

2. Consider using ponded and replant areas as a chance to pivot.

3. Reassess rootworm strategy: “catch crop” risk is real.

4. Treat pollination as “go time” for insect scouting.

5. Delay fungicide unless current disease pressure demands it.

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Keep Sulfur Available, Too

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1. Consider Moisture Availability, Not Just Planting Depth

2. Protect Uniform Emergence And Early Root Growth

3. Master The N:S Ratio And Starter ROI

4. Use Tech As A Guardrail, Not A Crutch

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Why Sulfur Matters More Now

Early Planting Amplifies Sulfur Response

Beyond Fertility: A Surprising Disease Connection

Big Upsides Where Sulfur Use Fills The Gap

Dynamic Duo: Research Shows 2-For-1 Benefit Pairing Ammonium Thiosulfate With UAN