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Optimize your soybean crop

Once you’ve chosen a soybean variety, seed at the right time and use 
the right inoculant to get the most out of your seed

The final Statistics Canada numbers for 2012 indicate a record soybean harvest across the country. In Manitoba alone, farmers harvested 800,000 soybean acres, a 40 per cent jump over 2011. Yields rose from 26.7 bushels in 2011 to 34.9 in 2012. More acres and yield added up to a record 759, 300 tonnes for Manitoba farmers.

As soybean acres grow in Western Canada, first-time growers have many questions. But their first question should be about which genetics fit their farm, says David Townsend, product manager with Becker Underwood in Clinton, Ontario.

Townsend says he prefers to spread his risk by seeding two or three soybean varieties, if they’re available. Farmers can seed different varieties to different areas, based on that variety’s performance in specific rotations and soil types.

Varieties are grouped into maturity groups, which are similar to the United States’ system. Maturity group 00 varieties can be grown in North Dakota and southern Canada.

“Now, at the same note, there are lots of people who are going to move it above the zone and be successful and say ‘Townsend wasn’t even close.’ And I know that’s going to happen and can happen,” says Townsend.

Townsend says the Trans-Canada highway is a rough boundary for how far north farmers can consistently grow soybeans in Alberta, Saskatchewan, and western Manitoba. Between Brandon and the Canadian Shield, the zone extends north to the Interlake region.

As earlier-maturing varieties are developed, soybeans will push north.

“And it depends a lot on if we continue to have this warmer environment. We seem to be in a warm trend as far as environment goes these last two or three years,” says Townsend.

Farmers should also consider their rotations before seeding soybeans. Soybeans fit in well after a cereal crop. White mould in soybeans is caused by the same pathogen as sclerotinia in canola and mould in field peas.

“And so if you’ve got a lot of canola and peas in your rotation and you throw soybeans in on top, the white mould will affect soybeans. At the same note, it doesn’t devastate soybeans because the petals of the flower are a lot smaller.”

However, moulding areas are usually the highest yielding areas because they’re so thick. Those areas will still yield, but not as well as they could have.

Before seeding soybeans, soil tests ensure there are enough nutrients in the soil. Ideally phosphorus levels will have been beefed up the year before planting soybeans. Any phosphorus applied during seeding should be banded so it’s available to the plants.

“It’s a difficult one because the response to phosphorus is hard to show, but it needs to get on there sometime because as those phosphorus levels get down, it is going to affect the soybean,” says Townsend.

Soil temperature

Getting soybeans to maturity is the biggest challenge to growers, says Townsend. But long sunlight hours are a big asset to Western Canadian farmers.

Though heat units help hasten soybeans to maturity, they are more sensitive to sunlight. The long days around June 21 trigger flowering, while waning daylight in September prompts the soybeans to mature. If frost hits before the soybeans have started shutting down, yield and quality suffer.

The biggest yield advantage a farmer can manage is the planting date, says Townsend. If the soil temperature is warm enough, planting in early May gives the plant more time to grow before it starts flowering in June.

“So they’re going to get taller, they’re going to have more nodes, more chances of branching, a bigger plant. If you have a big plant early, you’ve got your rows covered in, you’re intercepting more light, you’ve got more places for flowers to initiate, and that seems to give us more yield at the back end,” says Townsend.

In 2012, Brent VanKoughnet, owner of Agri Skills Inc., ran seeding trials for the Manitoba Pulse Growers near Carman, Manitoba. He seeded in late April, May 9, May 17, May 24, and May 30. He says seeding conditions were ideal through the whole stretch.

“And the yields went up marginally the later I planted. Partly because I think we got some rain at the end, and partly because in the later time slots the bean just exploded out of the ground in those hot, moist conditions. And by the end, even thought I’d planted over 30 days apart, by the end they could be harvested within three days of each other.”

But VanKoughnet wouldn’t delay seeding to June 1 if seeding conditions were good in mid-May.

“If I could go on the fifteenth of May, I’m going to start going. But I’m going to be pretty hesitant from the last of April to the 10th or 15th of May.”

Though Townsend suggests seeding in the earlier part of May, soybeans can’t be seeded until the soil is warm.

“The most important thing with soybeans is the first drink of water it gets. The temperature of the water it absorbs when it’s first put into the soil is more critical than the soil warming up later on,” says Townsend.

Even planting in the early morning can slow emergence if the soil is cool, Townsend says. Townsend says a gradient in plant populations can develop through a field, with higher populations in the areas seeded in the afternoon, when the soil was warmer.

Townsend doesn’t recommend 22-inch or 30-inch row spacing in Western Canada, partly because it’s harder to manage weeds. Both 15-inch and seven-inch rows are a good option. Rows set at seven inches help the canopy close more quickly and make it easier to control weeds. Townsend says 15-inch row spacings increase air-flow through the canopy, helping control soybean diseases like white mould.

Optimize emergence

The biggest thing with soybeans is to get them out of the ground, Townsend says. Seedlings have to push a large seed out of the soil. Townsend says he likes to see seed treatments on the seed.

“If you’re spending that much money, do it right. And then inoculate as well.” Farmers should check that seed treatments are compatible with the inoculants.

Inoculant formulations have improved, particularly for the liquid inoculants. Once applied to the seed, liquid inoculants will last up to 10 days before seeding. Extenders give farmers 30 days to plant. Formulations also contain more rhizobia than they used to.

Townsend says farmers should calibrate their air seeder metres before applying the granular inoculant to the soil, as application rates are low.

Townsend recommends double inoculations for new fields. Inoculant can be seed applied and banded.

“The biggest thing in Western Canada is we have not built up a population like we have in the Dakotas, in Midwest U.S., in Ontario,” says Townsend. Farmers who have grown soybeans for years still use a single inoculant rate, Townsend says.

Farmers who have been growing soybeans for several years in the same fields can start adjusting rates to see how the crop responds. Previous applications of other inoculants, such as those used for field peas, won’t help build up rhizobia populations for soybeans, as soybean inoculants use a different rhizobia species. †

About the author

Field Editor

Lisa Guenther

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.

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