Dormant seeding of spring wheat
By Carolyn King
Early planting is recommended for spring wheat production, but what about very early planting – so early that soil conditions don’t allow the seed to germinate immediately?
This practice is called dormant, or frost, seeding. Research and experience in Ontario and South Dakota show dormant seeding of spring wheat offers significant advantages in both those areas. Could it make sense on the Canadian Prairies too?
Dormant seeding in South Dakota
“Dormant seeding is the normal practice for spring wheat production at Dakota Lakes,”’ says Dr. Dwayne Beck, manager at the Dakota Lakes Research Farm at Pierre, S.D. As one of South Dakota State University’s research centres, the Research Farm’s primary goal is to identify, research and demonstrate methods of strengthening and stabilizing the agriculture economy. It is a no-till farm with both irrigated and dryland acres.
“We’ve been dormant seeding spring wheat since the 1980s,” explains Beck. “For us, it’s really important to have wheat in early because our weather goes from cold or cool to hot very quickly. So if we get a bit late on seeding the cereals, they get killed by hot weather in July in most instances.” Beck’s data show that yields for dormant-seeded spring wheat are better than for spring-seeded spring wheat.
Dormant seeding is also important for spreading out the workload at the Research Farm. The farm’s diverse rotations include many other cool-season crops, like peas, lentils and spring canola, that all have to be seeded in early spring. Plus, if seeding of the farm’s cool-season crops gets delayed, that could delay seeding of its warm-season crops as well.
Successful dormant seeding is dependent on the right environmental conditions. The field needs to be free of deep, wet snow. Uniformly distributed dry snow is OK. The soil needs to be cold enough so the seed won’t germinate, but not so frozen that you can’t properly plant the seed. At the Research Farm, dormant seeding is typically done in late November or early December.
“When we dormant seed, the soil is sometimes frozen, and if it isn’t, it’s ready to freeze. If it’s frozen and dry, it seeds really well. If the soil was wet when it froze, it doesn’t seed very well,” explains Beck. In frozen-wet soil, planting equipment can have difficulty achieving the recommended seeding depth of 1 to 1.5 inches, and Beck’s experience shows shallow seeding will fail. Fall is normally dry in South Dakota so frozen-wet soil is not usually an issue.
Beck’s other dormant-seeding recommendations include treating the seed with a fungicide, using a normal or slightly higher than normal seeding rate, applying a dry fertilizer (50 to 70 lb./ac of 11-52-0), and controlling weeds in the fall.
“We pretty much approach dormant seeding of spring wheat as if we were seeding it in early spring. We use the same varieties, about the same seeding rates, and so on. The seed doesn’t see a lot of difference between dormant seeding and early spring seeding – it just lays there a little longer,” he notes.
Beck has found that dormant seeding is best suited to no-till rather than conventional till systems. In South Dakota, dormant seeding requires enough crop residue to prevent soil erosion and to minimize soil temperature swings so the crop doesn’t germinate during a temporary warm spell in the winter.
Both spring wheat and winter wheat are grown at the farm. Beck’s data show dormant seeding of winter wheat doesn’t work well; it’s better to seed winter wheat in the fall in the usual way. When conditions aren’t right for fall seeding of winter wheat, then spring wheat will be dormant seeded.
Beck explains: “We normally grow winter wheat after a crop that has been harvested sufficiently early in the summer to allow some recharging of moisture and provide some time [for practices to control weeds, diseases and insect pests] before seeding winter wheat. For instance, it is almost impossible for us to harvest soybeans and then plant winter wheat – by the time you harvest the soybeans, it’s too late for planting winter wheat. That’s where spring wheat fits. Because soybeans are relatively low in residue, we often plant them after several years of high-residue crops so there is carryover residue from the other crops.”
Beck has tried dormant seeding of the other cool-season crops grown at the farm, with quite a bit less success than with spring wheat. One reason spring wheat does well is that its growing point stays belowground until the plant has four leaves and has tillered. So its growing point is still protected even if the crop starts to grow during a warm spell in the winter and then a frost hits.
Dormant seeding is a lot riskier for crops like canola that put their growing points at or above the soil surface as the plants emerge. “Canola’s growing point sometimes comes up too early in the spring, and then gets whacked by frost,” says Beck. “In high-residue situations, it will put its growing point above the residue even, and then it’s really vulnerable to frost damage.”
Other factors also affect a crop’s suitability for dormant seeding. Beck gives an example: “Field peas keep their growing point down and they truly stay dormant, but the seeds sometimes swell. If they swell and then the soil freezes, the seeds will split. We’ve had really bad luck with peas.”
Frost seeding for higher yields
Called frost seeding in Ontario, the practice works in that province too, even though conditions are moister than in South Dakota and the soil may be frozen wet.
Recent interest in frost seeding in Ontario was sparked by the yield benefits found in a study led by Dr. Bill Deen and Dr. Duane Falk at the University of Guelph. Their small-plot research involved four spring wheat varieties (milling and feed), two barley varieties and two oat varieties, which were grown at three sites per year, in 2003 and 2004.
“We compared frost seeding with a normal seeding date. The frost seeding date was April 1, plus or minus one week. The normal seeding date was the last week in April. I call that “normal,” but it’s a target seeding date for Ontario. Wet conditions may cause farmers to seed later than that. For Ontario, the rule of thumb is that every day of delay in seeding of a spring cereal leads to a bushel per acre of yield reduction,” explains Deen.
During the study, frost seeding took place when snow cover was gone, and a frost event occurred resulting in a 1- to 1.5-inch layer of frost on the soil surface. Deen explains that the soil has to be frozen enough to support the seeding equipment, but it can’t be frozen so hard that the no-till drill is unable to penetrate the frost layer to place the seed in unfrozen soil.
Other than the seeding date, all the practices for the frost-seeded and normal plots were the practices normally used for spring wheat production in the region. At some locations, they used no-till, with a fall herbicide application. At the other locations, they used a stale seedbed approach, where they tilled in the fall and then just planted into that seedbed in the spring.
In Ontario, most cereal production involves winter cereals, which are typically planted after soybean. The researchers thought one scenario where a frost-seeded cereal might fit into a rotation would be if a farmer harvests soybeans and then is unable to seed his winter wheat. So all of the cereals in the study were planted after soybean.
For all three cereals, the frost-seeded plots had significantly better yields. “The frost-seeded cereal was approximately two leaves ahead of the cereal seeded at the normal date. That relatively small difference had a very consistent and large impact on yield potential,” notes Deen.
“The results for wheat were the most pronounced. Across the two years, three sites and four wheat varieties, a 29 per cent yield increase was associated with frost seeding. Again, that is compared to a good normal seeding date. If farmers plant later, the yield advantage would be even more dramatic.”
He adds, “I’ve done many trials over the years and this is one of the few where yield response to management was consistently positive. It’s quite remarkable.”
Dormant seeding worked better on the no-till plots than on the stale seedbed plots. “You’re relying on a frost layer to provide load-bearing capacity for the equipment. Load-bearing capacity inherently is better on a no-till field,” notes Deen.
Along with improved yields, Deen says frost seeding results in earlier maturity and an earlier harvest of the cereal, and it allows more time in the spring for seeding of other crops.
Since this study by Deen and Falk, Ontario’s provincial cereal specialist, Peter Johnson, has done field studies at various Ontario sites to fine-tune frost seeding recommendations for seeding rate, seeding date, weed control, fertilizer management, seed treatments and so on. The recommendations for Ontario growers are available on the Ontario Ministry of Agriculture and Food’s website.
Limited adoption in South Dakota and Ontario
Even though dormant seeding works in South Dakota and Ontario conditions, it hasn’t been widely adopted in either area so far.
“A lot of things we’ve done [at the Research Farm] have become very well accepted by farmers, but dormant seeding isn’t one of them,” says Beck. “About 95 per cent or more of the guys in this area do practices like no-till and good crop rotations; that part of what we do has become standard. Although I know a few guys who dormant seed exactly as we do, there’s not a large number of them.”
He thinks several factors are hampering adoption of dormant seeding. One constraint is that crop insurance in the United States does not recognize dormant seeding as a normal practice.
Another factor could be that most South Dakota growers don’t grow as many cool-season crops as the Research Farm does. He says, “They might grow peas or they might grow lentils, but they’re not growing peas and lentils and flax and canola. So it’s probably less of a problem for them to seed a few thousand acres of wheat in the spring and then start their other crops.”
Beck also admits that seeding at the end of November isn’t an appealing idea for most farmers. “It’s late fall or early winter, and you’ve just finished harvesting your full season crops, like sorghum and corn. And the days are short, and you’re tired. Then some idiot wants you to drag out the seeder that you’ve got all cleaned up during the nice weather when you could use the power washer. He wants you to drag it out, fill it with fertilizer and seed, and go out to seed, when most of your seeding will be in the dark. It is really difficult to make yourself do that when you just want to kick back and have a cup of coffee.”
In Ontario, there aren’t a lot of acres of spring cereals in the first place. As well, there are some grower concerns with frost seeding. “The perception is that you have fairly limited windows of opportunity to use frost seeding. If the frost layer is too deep, then it’s hard on the equipment. If the frost layer is too thin, then equipment may get stuck if the operator fails to leave the field once the soil begins to thaw. If the frost layer is one to two inches thick, a no-till planter easily slices through,” says Deen.
“Our experience on this project was that the window of opportunity for frost seeding is not that limited. Our experience in Ontario – and I suspect it’s not that different out in Western Canada – is that you can have nights where at 6 p.m. the temperature goes below 0 degrees C, the surface freezes over, and you can plant all night. We’ve also had growers who were able to dormant seed through the day or over several days when frost layer conditions were good.”
Would it make sense on the Prairies?
With the potential for better yields, earlier harvests and spreading out the spring workload, is dormant seeding of spring wheat worth investigating on the Prairies?
“I’ve never had any researchers even talk to me about dormant seeding of spring wheat on the Canadian Prairies. I haven’t had farmers talk to me about it either, and usually it’s farmers who lead some of this stuff,” notes Beck.
He speculates that interest might be less on the Prairies because the potential yield penalty from delayed spring seeding isn’t as high because July isn’t usually as hot on the Prairies as it is in South Dakota.
However, Beck thinks the practice could offer benefits for some Prairie growers, especially if wet weather tends to delay their spring seeding operations. “Really the main reason we do it is to shift some of that spring workload. We do a lot of thinking about trying to shift the workload because machinery is expensive and labour is even more expensive because you can’t find enough labour.”
Deen thinks dormant seeding is worth examining under Prairie conditions. “Unless someone gives me a good reason why it absolutely wouldn’t work, I think the potential yield advantage is substantial enough that it’s worth investigating. I don’t see any reason why in Western Canada you wouldn’t see a similar response to frost seeding.”
In fact, Deen thinks it might even work better on the Prairies than in Ontario.
“In Ontario, our whole farming system is based on eliminating soil water in the spring. We are in a precipitation excess region – precipitation exceeds evapotranspiration over the winter and our soils tend to be saturated in the spring. When we spring seed, we have to wait for those soils to dry. Frost seeding enables us to get around that.
“In certain regions of Western Canada, the system is all about moisture retention,” adds Deen. “It seems to me that under those conditions, frost seeding would be even more advantageous and windows of opportunity may be greater since the frost layer on soils that are not saturated with water may be easier to penetrate with a drill. Furthermore, risk of getting stuck when the soil thaws is reduced.
“Honestly, I think it’s worth evaluating frost seeding under a number of the conditions typical of Western Canada.”
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