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Soybean success

Although soybeans have been grown in Manitoba for a number of years now, Saskatchewan farmers are just starting to access varieties that are suitable for their areas. As with all new cropping options, nothing is ever as simple as “do as I do.” There is significant research underway to find and test the best varieties as well as best practices.

Soybeans on soybeans

Brian Elliot is a Certified Crop Adviser, an agronomist with over 15 years of experience with soybeans and District Sales Manager with Northstar Genetics. We asked him about some common misconceptions as well as advice for success in Saskatchewan in particular.

“Proper rotations are always important considerations growers should practise for all cropping options,” he explained. “Soybeans have been and are being grown back-to-back, but that is definitely not a recommended practise.” There is a misconception potentially that growing soybeans back-to-back could help build-up rhizobia in the soil — the all-important bacteria that help the soybeans fix nitrogen in the soil.

Elliot has two things to say on that subject. “The rhizobia are not native to our soils, so while there may be some potential build-up in the soil year over year, there is a definite need to inoculate every year,” he says. “This is not an optional practise. In fact, we strongly advise double inoculation every year for soybeans. The success of this crop is determined in large part by having enough rhizobia in the soil to start nodulating and fixing nitrogen from the soil as soon as possible in the plants life.”

The other aspect of the possible misconception of rhizobia build-up in the soil by growing back-to-back soybeans is that because rhizobia are not native to our soils, their populations are negatively impacted in adverse weather conditions of extreme drought or water-logging as well as cold or overly hot soils. Because there is no way to measure the rhizobia populations, not their vigour, soybean inoculation is a requirement for success.

Six strategies for success

1. Know your heat unit area: There are maps available like the graphic shown from Saskatchewan Agriculture that show, essentially, corn heat units (CHU). Temperature is the primary limiting factor to soybean production, this this is a crucial starting point for any grower.

2. Review suitable varieties: Local trial data should be reviewed for heat units, day length sensitivity and maturity. Soybean varieties vary in their day length sensitivity,which is why local information is recommended. According to Northstar Genetics (www.weknowbeans.com) varieties with high daylight sensitivity will reach maturity without necessarily getting the ideal heat units and this adds to their success in non-traditional areas.

Soybean genetics for Western Canada have improved over the last 15 years. In the past, there were few varieties below 2450 CHU, now varieties are available in the 2300 to 2400 CHU range. There are ranges of maturity within heat unit classes as well, early-, mid- and long-season types. Elliot recommends growers balance maturity classes to offset the risk of early frost with higher yield potential from the later maturing types.

Soybeans are now being grown from the Manitoba border to Weyburn, with a lot of success in the Regina area to the southeast corner of the province. “There are some guys dabbling in soybeans as far west as Swift Current and in the Kindersley area too,” says Elliot. “We don’t have a lot of history in these areas yet, so it’s hard to say will soybeans work every year or not. This is the experimentation that is being done on-farm.”

3. Rotation: “I always advise to plant soybeans following a cereal of some sort,” says Elliot. “This helps avoid a lot of disease issues like root rot or sclerotina and things like nematode cysts.” Planting soybeans after canola, peas or lentils is not recommended, even though the soil will likely be warmer earlier as a result of less debris or trash.

4. Soil temperature and seeding depth: “This one is easy,” says Elliot. “Do not seed soybeans into soil less than 10 C.” Vigor and “pop-up” will be negatively affected. Soybeans should be seeded into moisture, but never any deeper than 1.5 inches. “Soybeans are very sensitive to depth of seeding,” explains Elliot.

5. Seed treatments: “This is key,” says Elliot. “I can’t emphasise this enough. Double inoculate soybeans for success.” Ideally, use a liquid inoculant on the seed as well as some sort of granualar or liquid in-row at seeding. Soybeans will use up to 200 pounds of nitrogen by maturity. With adequate rhizobia in the soil right at seeding, the crop will be compromised. Seed should also be treated for disease as there is ample opportunity for infections otherwise.

6. Handling: “This might seem obvious,” says Elliot, “but it’s not always taken into consideration. Handle the seed as gently as possible. Simply put, cracked seeds will not germinate.”

There are other considerations for growing soybeans that growers need to be aware of including their need for late season moisture, but if they take care of the six points above, they are well on their way toward a successful experience with soybeans. †

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