Plant soybeans too early and you can run into frosts, adverse soil conditions and other problems that jeopardize plant establishment and early development. It could even mean a washed-out field requiring replanting.

Plant soybeans too late, though, and you could be sacrificing yield, since there are fewer days before the crop’s critical seed pod filling period in summer.

Seth Naeve, a soybean agronomist and an agronomy and plant genetics professor with the University of Minnesota, has studied the benefits and risks associated with early soybean planting in northern climes such as Minnesota. He shared some of his research findings with farmers at the CropConnect 2025 conference held in Winnipeg in February.

A good decision

In an interview with Grainews, Naeve explained the main yield constraint for northern-grown soybeans is our shorter growing season. He says the argument for earlier planting dates is in how they can help soybean crops get a jump on germination and plant establishment when fields warm up enough for that to happen.

Naeve’s planting date research includes soybean field trials conducted at four Minnesota locations in 2023 and 2024. The findings showed, on average, planting as early as possible was “a good decision,” according to Naeve.

“We have this challenge in the north in that we have good long days in the spring, but there is just not enough heat there at the same time,” he says.

READ MORE: Check out our Soybean Guide.

“Soybean is actually quite tolerant of planting early and sitting in the soil for a long period of time,” Naeve adds. “Soybeans tend to not come out of the ground until the ground warms up significantly enough … to support germination and emergence. By that time, we tend to be outside of the risk of imminent frost late in the spring.”

Naeve noted a range of management tactics can be useful for lowering risks associated with early soybean planting.

“We can increase populations. We can use a fungicide seed treatment. We can plant shallow or deep, depending on where the moisture is and what the weather forecast looks like. So, there are a lot of things we can do to help reduce the risk that we’re imposing on these soybeans by doing this real early planting,” he says.

Naeve points out the value of early soybean planting may be limited at the earliest end of the seeding window — but it is an incremental value that accumulates over time.

Say, if a farmer decides to hold off planting for a day but is then unable to get back into the field for two weeks — that 14 days can make a significant difference in yield potential, Naeve says.

According to Naeve, the relatively low cost of seed is another risk management consideration for early-planted soybeans.

“Soybeans are relatively inexpensive to replant. If a farmer has a limited number of days to plant, it may be the best risk situation for them is just to plant soybeans early and hold off on some of their other crops like corn (so) they can be then planted under a little bit better conditions,” he explains.

Naeve had one proviso with respect to early-planted soybeans. Findings from the Minnesota study suggest yield responses to planting date are closely tied to how productive the soil is.

In high-productivity environments with good fertility and adequate moisture, early planting with full-maturity cultivars maximized yield. In low-productivity environments, early planting offered no yield advantage.

“If it gets dry or there is low fertility, this trumps any kind of advantage we get from early planting. It basically caps the yield,” Naeve says, noting stressors such as pest infestations and hail damage are also yield-limiting factors.

“If there are other problems that cap our yields, there’s just nothing that we can do. We can’t add more fertilizer. We can’t put on a fungicide. We can’t plant earlier. We can’t do any of those things if the yields are going to be capped by something else.”

Critical period

Naeve discussed some other aspects of his research, which include examining when northern-grown soybeans are maximizing their yield potential.

Naeve says field experiments in three Minnesota locations in 2022 and 2023 indicated the critical yield period was the R4 stage (when rapid pod growth and seed development starts) up to just before the R7 stage (when pods and seeds begin to turn their mature colour).

The testing also identified the R5.5 stage, which typically occurs in late August in Minnesota, as the most important time for soybean yield establishment.

“That corresponds to this idea that farmers have had forever that August makes beans, or late August makes beans, or rains in August make beans. All those things are very true, and we have some data now that really shows why that’s true,” Naeve says.

“If you can support that soybean crop during that most critical time, then it can really make a lot of yield for you,” he adds.

“The way I talk about getting a good crop is, we basically build the machine early in the year, and then at the end of the year, we’re just making seed. If we can get a really nice, large machine built and if we do have good conditions late in the year, then we can really take advantage of it.”

Iron deficiency chlorosis

Naeve also offers some recommendations for managing iron deficiency chlorosis (IDC), a nutrient deficiency that causes yellowing of soybeans leaves and stunted plant growth. In extreme cases it can result in serious yield losses in soybean crops.

He referred to a study by a master’s student of his, Maykon da Silva, called “Strategies for IDC from a Systems Approach: Variety Selection, Iron Chelates and Seeding Rates.”

The research, which involved experiments at 10 Minnesota field sites in 2021 and 2022, examined trade-offs and interactive effects between soybean varieties, populations and iron chelate rates across a range of IDC levels.

Iron chelate products can help mitigate IDC in soybean by maintaining iron in a soluble form that can be available to the plant early in the season.

Naeve notes FeEDDHA, or ortho-ortho iron chelate, is commonly used for this purpose, but he cautions not all of these products are the same. He recommends farmers look for products containing higher levels of iron in the ortho-ortho form, because they are generally more effective against IDC.

The IDC testing results suggest soybean producers would be wise to consider applying iron chelates to any fields with a history of IDC, he says.

The study, he adds, showed better crop results with iron chelates used as in-furrow treatment rather than a foliar application.

“There are a number of factors that all go together to make (foliar applications) not very good practice,” Naeve says. “It’s better just to put (iron chelate) in the soil where the plant can access it.”

Soybean foliage doesn’t absorb minerals such as iron chelate nearly as well as the plant’s root system, he says — and soybeans seriously afflicted with IDC don’t have much leaf material left in any case.

Naeve says findings from the Minnesota study also suggest choosing a variety with the highest rating for IDC control offers the best defence for soybean crops.

“It also comes with relatively little cost. Those (IDC-tolerant) varieties don’t necessarily have a yield penalty, so just picking the right variety is of utmost importance” — and this can be particularly true in fields with severe IDC conditions, he says.

Naeve stresses it’s also important to select “proven” soybean varieties that have been adequately tested.

“I think practically speaking, the biggest risk here is that farmers grow new varieties that are relatively untested for IDC. That’s one of the bigger issues, and that’s a problem we see with industry rolling out these varieties quite quickly.”

Naeve says he’s found that to be particularly true with new herbicide traits in soybean. “Those first varieties that come out tend to really lag for IDC tolerance and/or resistance.

“Certainly, in the United States, we have so many new varieties come out and sometimes they get pushed to the market without good testing,” he says. “I know Canadians have a much better program for releasing and testing soybean varieties than we do in the U.S. It is much more conservative, so hopefully those get weeded out better than what we have here.”

Another finding from the Minnesota study was that bumping up seeding rates to increase soybean populations can be a beneficial practice for managing IDC. The research shows a higher seeding rate had a small but consistently positive effect on yield.

“I think if they’re concerned about IDC, farmers can increase their seeding rates a little bit,” Naeve says. “It’s a small benefit, but it is large enough to pay for the additional seed cost.”

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As Daniel Kaiser, an associate professor and extension specialist in the department of soil, water and climate at the University of Minnesota, told farmers at the 2025 CropConnect conference in Winnipeg in February, research is shedding new light on how sulphur interacts with the soil.

While his work focused on Minnesota, it may have spillover implications for Canadian farmers. Sulphur is considered the third most limiting nutrient on the Canadian Prairies, and canola is highly sensitive sulphur deficiency, the Canola Council of Canada says.

Kaiser has been studying sulphur use and performance in his state for the past two decades.

“During that time, we’ve seen a fourfold increase in the sales of sulphur, and a lot of that is ammonium sulphate,” Kaiser says.

Misconceptions about sulphur availability

While much of this increase in sulphur use can be attributed to the growing production of sulphur-hungry crops such as corn, Kaiser suggests part of the rise may be due to misconceptions at the farm level.

However, because research shows negative ions, such as the sulphate in ammonium sulphate, tend to leach through soils that usually hold a positive charge, many farmers assume they need to reapply sulphur each year, thinking last year’s application has moved below the root zone.

READ MORE: How to develop sulphur fertilizer recommendations

“I don’t think that’s the case,” Kaiser says. “In terms of the reactions with some of the other elements of the soil, particularly in soils that have a lot of calcium, it hangs around a lot longer than we think it does.”

In response to this perceived leaching issue, some farmers turn to elemental sulphur, but Kaiser says there’s a potential drawback to this strategy. Elemental sulphur needs to be converted into plant-available sulphate by soil microbes — a process that doesn’t kick in effectively until soil temperatures hit 32 C.

“That’s a lot higher than what it’s going to be most of the time in the soils, particularly early in the growing season,” Kaiser says.

Sulphur sources

Kaiser outlined several sulphur fertilizer options.

Sulphate-based fertilizers, such as ammonium sulphate, potassium sulphate, calcium sulphate (gypsum) and Micronized Sulfur Technology (MST), provide sulphur in the sulphate (SO₄) form, which is immediately available to plants. These fertilizers are typically the most effective for addressing sulphur needs during the growing season. In terms of sulphur response, all sulphate-source fertilizers tend to act similarly.

As pointed out above, elemental sulphur must undergo the slow process of microbial conversion into sulphate, making it a slow-release fertilizer.

Thiosulphate (S₂O₃) is another option. Although, like elemental sulphur, it also needs to be converted by soil microbes into sulphate, thiosulphate behaves more like a sulphate fertilizer in terms of plant response. It tends to be faster-acting than elemental sulphur and can provide sulphur to plants in a timeframe similar to that of sulphate-based fertilizers.

For the purposes of his research, Kaiser used mainly potassium sulphate for his sulphate-based fertilizer. For elemental sulphur, he mainly used Tiger 90, a granular product that’s 90 per cent elemental sulphur mixed with bentonite.

Carryover confidence

Kaiser’s research on sulphur use in rotations backs up his suggestion that sulphur leaching may not be as big a concern as some farmers think. He’s been tracking sulphur responses across various crop rotations.

He found sulphur applied in one year can carry over to benefit subsequent crops, even when no sulphur is applied the following season. For example, in a corn-soybean rotation, yields were higher in the second and third years when sulphur had been applied to the previous corn crop, even though no additional sulphur was applied to the soybeans. Kaiser says he’s collected extensive data from sites across Minnesota, all showing sulphur doesn’t leach out of the soil profile between seasons.

“This speaks to that carryover effect,” Kaiser says. “While sulphur is an ion and technically susceptible to leaching, we’ve seen time and again that it stays in the soil and is available for crops in subsequent years. So, I’m not concerned about leaching in these systems.”

Issues with elemental sulphur

Another study Kaiser conducted across several Minnesota sites provides insights into how different sulphur sources perform under various conditions. For instance, the Tiger 90 consistently lagged behind the sulphate sources such as MST and potassium sulphate.

At one site near Waseca in south-central Minnesota, the Tiger 90 showed little to no availability of sulphur in the first year — and even in the second year, its sulphur availability was only about half that of MST or sulphate fertilizers.

This slower release of sulphur from Tiger 90 underscores an important point: while it can be a good long-term investment, growers are unlikely to see a return on investment in the year it’s applied.

For farmers who need quicker results, MST or sulphate-based fertilizers may be a better choice in the short term.

The post Do farmers need to apply sulphur to their crops every year? appeared first on Grainews.

“If farmers are dealing with major ruts, they definitely do take it seriously, but I think their concern has more to do with having a good seedbed prepared for the following spring and the impact on equipment operations in the field due to the ruts,” says Marla Riekman, a soil management specialist with Manitoba Agriculture.

Instead of only considering the immediate downsides of ruts, farmers should also be aware of their long-term costs.

A tire rolling through wet ground functions a lot like a barge pushing through water. The rotation of the tire pushes a wave of soil up ahead of the tire. The tire then climbs the wave, pushing soil sideways and leaving a rut behind. While a rut, like any ground that has been run over by equipment, does have some compaction from the weight of the machinery, the bigger issue comes from the soil displacement.

“A rut is more of a smeared, deformed soil than a compacted soil,” says Jodi DeJong-Hughes, a regional extension educator with the University of Minnesota. “The loss of soil structure translates to a significant decrease in yield: right in the rut areas you’ll see about a 16–17 per cent yield hit that’ll last for about three years.”

When soil is displaced, chunks are broken into fine particles and air is squeezed out. When ruts are mechanically filled in, the additional movement causes more of the same. Though you might not be able to see ruts once they’ve been filled back in, the displaced soil’s fine texture and low air content mean it will warm more slowly, stay wet longer, support more root and seedling disease, decrease plants’ nutrient uptake and compromise water infiltration, all ultimately leading to decreased yield.

“What we see is that ruts don’t hurt overall crop population — seeds can germinate — but [plants growing in ruts] have trouble with rooting and getting going. They are one to two growth stages behind the rest of the crop. If you’re behind by one growth stage in corn, for example, that plant is considered a weed. They can absolutely be behind by that much,” says DeJong-Hughes. “Ruts also create more soil disease, because disease can really take off in cooler, wetter soil.”

It can be tempting to rip deep ruts deeper to break up the compacted rut area and smooth the surface. Resist the urge.

“Just fill them in. That’s the best you can do. You are going to have a yield hit; there’s no getting around it,” says DeJong-Hughes. “The No. 1 defence against compaction and rutting is soil structure. The more you disrupt the soil, the more you destroy its soil structure so that the next time you’re out in wet conditions, the deeper you’ll create new ruts.”

“Zero till farmers definitely have an extra challenge when it comes to cleaning up ruts,” adds Riekman. “Generally, we recommend light tillage, just deep enough to fill the ruts in, running parallel to the ruts so that they only are tilling the rutted areas.”

More importantly, producers should do all they can to minimize ruts in future. The wetter the ground, the more rutting will occur. Though producers don’t always have the option to leave a field that needs seeding or harvesting, the long-term yield cost of ruts should be considered. The 15–16 per cent yield loss over three years just might justify the inconvenience of leaving the wettest parts of the field for last, the risk of waiting an extra day or two to get into a field and/or the investment of switching to controlled traffic farming.

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“Researchers have found an inverse relationship between yield and protein, so as one goes up the other goes down,” said Tkachuk. “Selecting for yield has likely led to a decline over time.”

However, she says, the relationship between varieties with higher yields and lower protein doesn’t always hold. “I think there’s more to the story than that.”

Other hypotheses include Western Canada’s shorter growing season, soil type and temperature. The shorter growing season in the north could mean that the plant has less time to allocate energy and resources into protein synthesis in the seed.

Soil type could also be a driving factor, she added, pointing to the soil’s ability to retain soil moisture. “Moisture appears to be pretty closely related to protein, and different areas experience different precipitation,” she said.

Temperature may also contribute. “In Manitoba, for example, farmers grow shorter-season varieties that now have higher yield potential than they would have before, but these are all factors that are interacting and contributing to lower protein,” she said.

Tkachuk evaluated data sets from several Manitoba research trials to see what parameters impact protein. These studies looked at plant population and planting dates, as well as fertilizer studies that evaluated phosphorus, potassium and nitrogen use.

“None of these factors really did anything to protein; there were no clear trends,” said Tkachuk. “In a nutshell, my big takeaway for farmers is that agronomically speaking and management speaking, you can’t plant earlier to get higher protein.

American researchers have also been struggling with protein levels in the more northern climates. A project spearheaded by the University of Minnesota has found that the mechanism used to measure crude protein levels may not actually be the best measure.

“They actually found that the U.S. had higher amino acid content than Brazil, which suggests a dietary benefit for livestock and human consumption,” said Tkachuk. “The results could present an interesting marketing opportunity for the more Northern-grown beans,” she said.

Can you increase protein?

Shawn Rempel, general manager of Quarry Seed Ltd., believes there agronomic practices could boost protein levels — or at least give farmers the best chance of producing adequate levels in their soybeans.

“As soybeans are legumes and fix their own nitrogen, there is a strong correlation to higher protein in conjunction to a longer nitrogen fixation period for the soybean crop,” he said. “We’ve found that in 2018, growers who planted soybeans on land with previous soybean history, used a strong inoculant program and experienced very early nodulation, had the highest protein results.”

Rempel also pointed to fertility as a possible solution. “In most cases the addition of nitrogen fertilizer won’t do much to increase protein content,” he said. “However, starting with adequate nitrogen levels will be a benefit.

Rempel says long-term data shows that strong inoculant programs pay off in terms of yield and “generally with potential protein content.”

“There’s been work to show that protein will not increase with the use of inoculants on land with previous soybean history,” he added. “That may be true, but in general, the land with soybean history is generally in geographies where low protein is a minor issue. The geographies with limited soybean history are generally the areas showing us lower protein results, such as western Manitoba and Saskatchewan.”

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Seed treated with fungicides or insecticides should never be allowed to enter the feed or food chain. In a recent blog, Lizabeth Stahl, an extension educator at the University of Minnesota wrote: “Treated seed is not to be used for food, feed or oil processing, and care must be taken to not contaminate grain going into the food or feed market. There is ZERO tolerance for treated seed in the export market, meaning that a single seed could result in the rejection of an entire load.”

Farmers should cover up treated seed spills with soil to ensure that birds and other wildlife don’t consume them. For unwanted, leftover seed, there may be several options for farmers to dispose of it both on and off-farm. One of the most important things is that farmers read the seed bag label so they know exactly what the seed has been treated with and the recommended practices for disposal.

One of the best disposal options is to plant the treated seed on fallow or unused ground, but Stahl advised, depending on the seed treatment, there may be restrictions on planting rate and depth. Some seed may be suitable for burial (again check the label) but should not be buried close to any water source.

Treated seed should never be composted or burned in a heating stove used inside a building (home, shop etc) because it can give off toxic fumes.

There may be a number of options for producers to dispose of treated seed off-farm, including disposal at a landfill site (depending on provincial regulations — see below). Some power plants and ethanol plants may also take treated seed as a fuel source.

The following is taken from the Canadian Seed Trade Association’s Guide to Treated Seed Stewardship, which includes guidelines about how to dispose of unwanted seed that has been treated with fungicides or insecticides.

Small quantities

For small quantities of unused, treated seed, the guide recommends:

1. Return excess treated seed to its original seed lot containers if the seed is intended for storage and subsequent planting.

2. Plant in fallow or other non-cropped areas of the farm in accordance to the seed treatment product label.

3. Unless restricted by label language, excess treated seed may be double planted in the turn rows at the end of the field or within a portion of the field.

Large quantities

For larger quantities of treated seed not acceptable for planting, the guide says:

1. Large quantities of treated seed in sealed and undamaged packages, bags or totes, in many cases, may be returned to your supplier.
2. Consult with your provincial authorities to ensure your disposal plan is in compliance with all appropriate regulations.
3. Disposal facilities will be required to have a Ministry of the Environment (or similar) permit to accept pesticide treated material (such as treated seed). Whether a waste management facility, power plant, cement kiln, ethanol plant, or municipal landfill is permitted to dispose of seed treated with a particular pesticide can only be confirmed by contacting the facility.
4. Your seed supplier may also be aware of permitted disposal facilities in your area. Treated seed can be land filled at a Class I or II landfill if it is classed as non-hazardous waste according to Provincial waste control regulations. If it is classed as hazardous waste by provincial regulations, check with provincial waste disposal regulations and agencies to determine if it can be disposed in a Class 1 landfill, and to determine locations of Class 1 landfills.

Remember, there is zero tolerance for treated kernels in the commodity grain channel when the treated seed tag states the seed is not for food, feed, or oil purposes.

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Sometimes it’s hard to realize that post-weaning heifers from two to six months of age are not miniature milk cows. Rather, these young replacement heifers have immature rumens, which takes up to six months of age before they are fully developed and functional; contain enough rumen microbes, digestive enzymes and volume to consume and efficiently digest all types of forages and other feedstuffs.

Keeping this in mind: a young dairy heifer diet should contain enough starch-enriched feedstuffs to promote rapid and continuous rumen development.

Don’t want them fat

Most viable dairy heifer replacement programs still target a modest growth rate for post-weaning heifers of 1.8 – two lbs. per day (increased to two – 2.2 lbs. after puberty at about nine to 10 months of age). Feeding diets with excessive energy to make them grow much faster should be strictly avoided. Overweight heifers tend to lay down fat in their developing udders, which irreversibly reduces their capacity to produce milk in their first and future lactations.

Most ruminant scientists acknowledge dairy heifers gaining more than what’s considered the “safe” limit of 2.2 lbs. per day may actually lay down more lean muscle compared to replacement heifers on a more growth-controlled program and save on overall feed and housing costs. However, they also agree chances are very good more fat heifers are produced by promoting such rapid growth.

But don’t short-change your post-weaning heifers, either!

A sound heifer grower diet for two-to-six month old animals should contain enough dietary energy of 67 to 69 per cent TDN (total digestible nutrients), 16 to 18 per cent protein, and be fortified with adequate levels of macro- and trace-minerals and vitamins. Also keep in mind young dairy calves from weaning (180 lbs.) to six months (400 lbs.) of age have a limited dry matter intake from about six to 10 lbs. per head per day.

Pick a proper diet

There are many practical diets for two-to-six month old heifers that promote good rumen development and growth performance at the same time. For example, a University of Minnesota field trial fed 90 dairy replacement heifers from three to six months of age, weighing on average 222.2 lbs. for 84 days on a balanced ration consisting of free-choice high-quality hay (16.7 per cent CP) and a 18 per cent grain ration (based on cracked corn and soybean meal) fed up to five lb./head/day.

Average daily gain was relatively consistent among the study heifers; recorded at 2.1 – 2.2 lb./head/day. Addition of some dried distillers grains to replace some of the soybean meal in the diet as an alternative protein source did not affect growth at all. Such demonstration also proves that high-quality forages and sufficient amounts of grain are required in order to achieve an acceptable level of performance.

In contrast, I am not an advocate of feeding two-month old dairy heifers a total mixed ration (TMR) containing silage, either specifically formulated for them, or producers that simply feed them lactation leftovers. In particular, I believe these young post-weaned heifers have limited rumen capacity, which is not fully developed in the first place and bulky TMRs containing silage challenges their daily intakes in order to obtain enough essential nutrients. As proof, I have on occasion seen young heifers with their “big balloon” bellies filled with silage and gas.

Another reason not to feed TMRs is some ensiled feeds such as high-grain corn silage contain excessive energy and often not enough protein, which could possibly over-condition young growing heifers. If a dairy producer wants to feed a TMR/ensiled feed, I recommend waiting until heifers become older; four to six months of age, so silage might be formulated up to 25 per cent of the total forage dry matter consumed.

Regardless of what post-weaning diet is ultimately fed, the best diet for dairy replacement heifers is also largely based upon knowing how the animals look at any given time. Dairy heifers should have a body condition score of three to 3.5 (based on a five-point scale; one = thin, five = fat). If they appear not to be growing or are thin; dry matter intake records and the entire diet should be reviewed.

Diet and management

Dairy producers should also parallel proper diet with good post-weaning heifer management. Many dairy specialists and I recommend to first wean six- to eight-week old heifers still consuming about a kilo of calf starter for a few days.

Wait a couple of weeks before removing them from hutches or individual stalls and then segregate them into small groups according to their size and weights. All of these young dairy candidates should be moved into groups of no more than five to seven heifers per pen. These pens should finally have adequate space for animals to move around and rest, be clean and well-bedded, with water provided on a free-choice basis.

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But is tillage an effective solution to these problems? And do the potential benefits outweigh the risks?

Tilling to warm soils

Farmers dealing with sopping wet soil might want to try tilling, Dr. David Lobb told delegates at the Manitoba Agronomists conference in December 2014. Lobb is with the University of Manitoba’s Department of Soil Science.

“Crop residues shade the soil and keep it moist. You have a cool, moist environment which usually delays seeding,” said Lobb. Since tillage buries crop residue and exposes soil to air, it should help warm and dry it, Lobb explained.

But research into using tillage to manage wet soils hasn’t yielded conclusive benefits. Some studies have shown tilled soils tend to be slightly warmer and dryer than no-till soils, Lobb said. But differences are often insignificant and results are inconsistent, he added.

Farmers might see some small improvement by managing extra moisture through tillage, he said. “But what’s going to override how wet your soil is isn’t the tillage system so much as the weather. If you have wet weather, you have wet soils.”

Tillage brings risks to the Prairie pothole region and the Red River Valley, Lobb said. For one, it accelerates soil erosion. Without residue cover, farmers will more likely see wind and water erosion. Tilled hilltops are more likely to erode. And in the Red River Valley, “tillage is actually what fills in a lot of those surface drains, particularly at the field edges where you get a bit of damming,” said Lobb.

In wet years, water draws salt to the soil surface, causing salinity. Tilling those areas can increase salinity, said Marla Riekman, land management specialist with Manitoba Agriculture, Food and Rural Development. The salinity caused by tilling around wetlands can outweigh potential benefits such as drying, she added.

Lobb said tilling to eliminate ruts is a good way to keep fields operational. But tilling when soils are still wet will make the problem worse. Instead, he suggested targeted tillage when the soil is slightly frozen. “You can actually level out those ridges and ruts a little bit.”

Compacted soils

Some farmers are concerned about compaction in their fields, especially as equipment gets heavier. Compaction happens when soil particles are squeezed together, compressing pore space. But slightly compacted soils promote good contact between seed and soil, the University of Minnesota’s website notes. A little compaction can also cut water loss from the soil.

But in wet years, yields drop with any increase in compaction, the University of Minnesota notes, because it leads to more denitrification. In dry years, some soil compaction boosts yields. But too much soil compaction cuts yields in dry years, too, according to the university.

Tillage, raindrops and minimal crop rotation can all cause some form of compaction, the University of Minnesota notes. But wheel traffic is the major cause, as machinery grows heavier and farmers are pressured to start seeding before soil is dry enough to support the equipment.

“The challenge is not actually causing the compaction in the first place,” said Riekman.

Farmers should keep in mind that 80 per cent of compaction happens on the first pass, Riekman said. She suggested making sure tractors aren’t over-ballasted.

Running tires at the rated pressure is also important. Riekman said when tires are at the rated pressure, they don’t cause any more compaction than tracks. Often tires are over-inflated for the field, she said.

As for vertical tillage, Riekman warns that many units are actually more like high-speed diskers than true vertical tillage implements. Faster soil movement has the potential for higher erosion, she added.

The University of Wisconsin’s Discovery Farms looked at shallow vertical tillage on five Wisconsin farms. Researchers concluded that “aggressively designed vertical tillage implements will disturb more soil and surface residue” than other designs.

Machines with aggressive blades and rear attachments and gangs angled at more than 180 degrees disturb soil and crop residue more than other vertical tillage implements, the Wisconsin researchers noted. Conservative and shallow are key words when using those implements in fields likely to suffer soil loss, the reports states.

Making two or more passes with vertical tillage implements can boost soil disturbance and reduce residue, similar to tandem disking, Wisconsin researchers noted. Aggressively designed vertical tillage equipment will move soil laterally on the first pass, they added. One shallow pass with non-concave coulters didn’t move much soil laterally.

Riekman said researchers haven’t found any fracturing below the coulter. As well, one of Riekman’s colleagues and a summer student used a penetrometer to see whether vertical tillage cut compaction in a field. Three weeks after the field had been tilled, they couldn’t find any signs that compaction had been decreased, she said.

Subsoilers also fall into the vertical tillage category, but they’re meant to dig deeper into the soil profile and fix deeper compaction issues.

“Will it help? Maybe. But the end game is we’re trying to gain yield here,” said Riekman.

Farm trials in Iowa found subsoilers had a 50 per cent chance of bumping yield high enough to offset costs, she said. Subsoiling is very expensive, Riekman noted, partly because it takes a lot of fuel to run the implements up and down the field. Rather than working the whole field, farmers should focus on headlands and other areas that are more compacted, she suggested.

The University of Minnesota’s extension website also noted that although subsoilers can break hard pans, subsoiling doesn’t boost yield consistently or for long periods of time. Irrigated loamy soil is one possible exception, the university noted.

There may be several reasons for the lack of yield gain, such as recompaction, insufficient depth of subsoiling, high soil moisture levels while subsoiling, or worsening of soil properties because of subsoiling, the university’s website states.

Subsoiling can help by shattering a hard pan, Riekman told delegates. But farmers shouldn’t go more than an inch below the hardpan, she added. Going too deep might create more compaction, she said.

The University of Minnesota suggests the following steps for successful subsoiling:

1. Make sure there’s actually a compaction problem. Do visual crop symptoms match wheel traffic? Is there standing water in wheel traffic patterns?
2. Make sure subsoiling will loosen up the compacted layer.
3. Soil should be dry and fracture to the shank’s depth during subsoiling.
4. Use controlled traffic to avoid more soil compaction.

The University of Minnesota Extension has soil compaction information available on its website by clicking here.

University of Wisconsin’s Discovery Farms research is available on its website by clicking here.

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