“Western Canada has gone from having not optimal to better protein levels over time and we’re getting very close to the average U.S. protein,” said Jim Everson, executive director, Soy Canada. “Unless we get protein levels up, we’re likely to take discounts on international markets.” | READ MORE
"In the last decade, the University of Illinois has collected data on agronomic performance, including yield, but also data on the resistance of the lines as well as on SCN pressure in the field. We've built up a massive dataset from these tests," says University of Illinois soybean breeder Brian Diers.
By looking at 11 years of data from 408 sites around the Midwest, the researchers found that there was a yield advantage for SCN resistance even at low infestation levels--as low as 20 eggs per 100 cubic centimeters of soil. In environments with no SCN infestation, the team saw evidence of yield drag, where resistant varieties yielded slightly less than susceptible ones.
"But most fields in the Midwest do have at least some infestation," Diers says. "So, in most cases, there's little justification in planting susceptible varieties to avoid that potential yield drag." | READ MORE
Besides the lack of rain in Ontario, one of the major players for soybean stress was the presence of spider mites. The most important factor to keep in mind for mites is to scout for them, since drought-stress holes can look very similar to spider mite damage. Once farmers notice stippling and discoloured patches, it’s important to take care of them as soon as possible.
“Spider mites are not an aphid pest, where you would wait for the threshold to build and then you take action,” Kowalski says. “You have to continually assess it and make an action decision because they won’t go away.”
She also says many agronomists thought aphids would be the big problem for growers due to the hot and dry year, which just goes to show that it can be difficult to predict pest problems from year to year.
With spider mites, Kowalski says it’s important to spray a dimethoate like Cygon or Lagon, and avoid a pyrethroid (like Matador) since it will also take out the predatory mites, increasing the spider mite pressure.
The second factor that came into soybean management this year had to do with fungicides. “Weather is only one factor of the fungicide decision,” Kowalski says. “Just because it’s a dry year, I wouldn’t write out a fungicide [prescription].”
Growers and agronomists should be looking at history (of white mould for example), row spacing and emergent population. Again, getting out and seeing what’s already in the field is important, since every year brings a different challenge.
“Proactively scouting and managing the crop throughout the growing season is never a bad idea,” Kowalski says. “Even if the growing conditions are ideal, scouting can be a very useful tool to identify ways to maximize yields economically.”
Don’t forget about the disease history of your fields either: If a field had soybeans or even canola previously, there is a likelihood that sclerotinia (the hard black bodies created by the white mould fungi) will be present following a diseased year and cause infection in that subsequent soybean crop.
Base fertility and soil health also play a role in mitigating stress in soybeans, especially in a drought year. The more soil organic matter available, the better the water retention, which helps limit drought stress due to the availability of moisture to those crops. Good fertility also means strong early season root growth and adequate nutrient levels in the root zones, resulting in more efficient water use, better nutrient uptake and less of a chance of deficiencies and stress. Early data shows managing phosphorous (P) and potassium (K) levels in soil at higher background levels has led to a good response in crops versus the current recommendations (sufficiency approach) that were established more than 30 years ago, when yields were lower.
Every year brings a different challenge for soybeans and other crops: 2014 was a terrible white mould year, 2015 had significant spring frost events and aphids and 2016 was a droughty year, so proactively scouting and managing the crop throughout the growing season is never a bad idea, Kowalski says. “Even if the growing conditions are ideal, scouting can be a very useful tool to identify ways to maximize yields economically.”
2016 was a year of extremes for Ontario soybean growers. Incredibly dry conditions in some regions resulted in poor yields or total crop failures in the most extreme cases. In contrast, a dry spring with few diseases, followed by timely rainfall in August resulted in amazingly high yields in parts of southwestern Ontario. Soybean yields are notoriously difficult to predict before harvest so much of the industry was pleasantly surprised at these good yields considering the growing season. Field averages of over 70 bu/ac were reported and yield monitors pushed over 100 bu/ac in the best part of some fields. Current estimates have the provincial average for 2016 at 44.8 bu/ac (with 56 per cent of the reports in from insured growers). This is slightly above the 10 year average of 43.9 bu/ac for those growers. The five year average for the province is 46.6 bu/ac. Soybeans are by far the largest field crop grown in the province with 2.715 million acres seeded in 2016. This was the third largest soybean crop in history. 2014 was the largest at 3.06 million and 2015 had 2.90 million acres.
Higher yields result in greater nutrient removal. Although soybeans take up almost twice as much potassium (K) as phosphorus, both nutrients are essential for soybeans. Factors that limit root growth such as dry conditions and sidewall compaction will reduce uptake. Under dry conditions, roots are unable to take up K from the soil even if soil K levels are sufficient. A soil test is the only reliable way to know if a field is truly low in K or just showing stress-induced potash deficiencies. It’s also important to note that K deficiency symptoms may be an indication of soybean cyst nematode (SCN) feeding on the roots. When taking soil samples, ask the lab to also test for SCN. A spring or fall application with incorporation work equally well to feed soybeans if soil tests warrant fertilizer.
The micronutrient manganese (Mn) is also critical for soybeans. Large parts of Ontario’s main soybean growing areas are deficient in Mn. Symptoms of Mn deficiency is interveinal chlorosis (yellowing). One of the most significant factors affecting the availability of Mn is the soil pH. As soil pH increases, less Mn is available to the plant. Deficiencies may occur on eroded knolls where the pH is higher than the rest of the field. The deficiency is most common on poorly-drained soils, especially on clays and silt loams. High organic matter also ties up Mn. Since only small amounts of Mn are required by the plant, a foliar application of Mn works well to rectify the deficiency. In severe cases, a spray application can provide a five or more bu/ac yield response.
Seedcorn maggot was more of a problem this spring than usual. Seedcorn maggots feed on germinating corn and soybean seeds and young seedlings. Damage can range from minor feeding which delays emergence to seed death. Seedlings that do survive are often severely weakened and may not fully recover. Seedcorn maggot numbers are impossible to predict but a mild winter likely increased populations in the spring of 2016. Maggot feeding results in hallowed out seed with small dark channeling. Flies are attracted to the odour of decaying organic matter that has recently been incorporated, such as freshly tilled soils, decaying plant residue, lightly tilled cover crops, and manured fields. The eggs are laid in moist soil and once hatched begin to feed on germinating seeds. For growers that consistently experience seedcorn maggot damage, an insecticide seed treatment is the only reliable control option. It’s also important to note that treated seed may not give complete protection under extreme insect pressure so higher seeding rates should also be used.
In dry years, some pests proliferate quickly. Spider mite damage was widespread this August. Mites feed on individual plant cells from the underside of leaves leaving stipples. Severe stippling causes yellowing, curling and bronzing of leaves. Spider mites usually start on the edge of the field but wind can carry them to any part of the field. From the road these pockets may look like moisture stress. Fields that are close to neighboring winter wheat stubble, hay fields and no-till fields are more at risk. Foliar insecticide applications were necessary on significant aces this year.
Double cropped soybeans
A number of growers were able to achieve 35 to 40 bu/ac this year, when seeding after winter wheat harvest. One of the reasons double copping is becoming more successful now than 20 years ago is due to higher yielding short season varieties. Plant breeding efforts for northern climates, especially western Canada have resulted in better short season varieties that can be seeded later in the growing season. Fields planted after July 15th or fields that remained extremely dry throughout the growing season were generally not successful.
Soybean variety selection continues to be one of the most important management decisions a grower can make to achieve high yield. The Ontario Soybean and Canola committee conducts performance trials each year across the province. Results from these trials can be found at gosoy.ca. Within a single test yield differences of over 10 bu/ac between varieties are not uncommon. Longer maturing varieties yield significantly more than shorter maturing varieties in most regions. Generally, longer maturing varieties yield 0.4 to 1.0 bu/ac more for each day they take longer to mature in the fall. For fields not intended for winter wheat seeding selecting a longer season variety is a cost effective way to increase yields.
The new discovery, reported in the journal Nature Plants, contradicts a widely accepted hypothesis about how climate change will affect food production, said University of Illinois plant biology professor Andrew Leakey, who led the new research.
“If you read the most recent Intergovernmental Panel on Climate Change reports and if you read the scientific literature on the subject for the last 30 years, the concluding statement is nearly always that elevated carbon dioxide will ameliorate drought stress in crops,” Leakey says. | READ MORE.
Most fields are now in the R2 (full flower) to R3 (beginning pod) growth stage. Vegetative growth has been highly dependent on the amount of rainfall in a given region. Moisture stress and leaf yellowing is evident in many fields. Soybeans flower over an extended period of time giving the crop the capacity to recover from early season moisture stress. Large yield losses do not generally occur unless moisture stress continues into the R4 (full pod) growth stage. This is only true if adequate plant stands are present. If stands are thin, or plants are suffering from other issues, losses will occur earlier. Weather conditions over the next four to five weeks will be crucial to seed development and will play a bigger role in final yield than the first half of the growing season. Dry conditions will amplify nutrient deficiency symptoms, insect feeding, and disease symptoms. When plants are already stressed it’s even more important to manage deficiencies wherever possible.
Manganese (Mn) and potash (K) deficiency are widespread this year. These two nutrient deficiencies have unique leaf symptoms. K deficient leaves turn yellow along the leaf margins while Mn deficient leaves turn yellow across the whole leaf except for the veins which remain green (picture #2). Factors that limit root growth such as dry conditions and sidewall compaction will reduce K uptake. Under dry conditions roots are unable to take up K from the soil even if soil K levels are sufficient. A soil test is the only reliable way to know if a field is truly low in K or only showing stress-induced potash deficiencies. It’s also important to note that K deficiency symptoms may indicate soybean cyst nematode (SCN) feeding on the roots. When taking soil samples ask the lab to also test for SCN. It’s difficult to alleviate K deficiency now since foliar products cannot supply enough K through the leaf tissue to rectify the problem. A dry application of potash on later planted fields may still be warranted in severe cases. Yield response will depend on the amount of rainfall after application.
Symptoms of Mn deficiency are interveinal chlorosis (yellowing). Mn is immobile in the plant so symptoms will generally appear on the younger leaves first. One of the most significant factors affecting the availability of Mn is the soil pH. As soil pH increases less Mn is available to the plant. Deficiencies can also appear on eroded knolls where the pH is higher than the rest of the field. The deficiency is most common on poorly-drained soils, especially clays and silt loams. High organic matter also ties up Mn. Manganese is less soluble in well-aerated soils; and is the reason why in compacted areas (wheel tracks) a dark green colour may remain while the rest of the field becomes symptomatic. A foliar application of Mn works well to rectify the deficiency and can provide a 5 to 8 bu/ac yield response in severe cases.
In dry years insects often proliferate quickly. To date spider mite damage has been limited, but field scouting will be important especially if conditions remain dry. Mites feed on individual plant cells from the underside of leaves leaving stipples. Severe stippling causes yellowing, curling and bronzing of leaves. Damage is most severe under hot dry conditions. Spider mites usually start on the edge of the field but wind can carry them to any part of the field. From the road these pockets may look like moisture stress. Fields that are close to neighboring winter wheat stubble, hay fields and no-till fields are more at risk. To verify mites, take yellow leaves and put them over a white piece of paper and then shake the mites off the leaf. Small mites will be visible crawling on the piece of paper. They are only about one millimetre in length so a hand lens may be required. Four or more mites per leaflet or one severely damaged leaf per plant prior to pod fill indicates that control is required.
Soybean aphids have only been reported in a few fields to date. Soybean aphid populations above threshold numbers (250 aphids per plant with increasing numbers) will cause yield losses until the R6 (full seed) growth stage. Soybean aphid management is essential in dry years since yield losses are highest when plants are already stressed.
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