When seeding soybeans later in the season farmers should consider increasing their seeding rate to bolster yields, a Manitoba Pulse Growers Association production specialist says.
Kristen Podolsky said in an interview getting canopy closure by the first week of July is key to getting good soybean yields.
“Soybean flowering is triggered by day length. As soon as the days start to shorten on June 21, flowering will be triggered regardless of when they were planted,” she said. “The problem is those planted later will have less vegetative growth. To curb that and maximize our yield potential we may want to increase our seeding rate… to get more of that growth.”
A closed canopy suppresses weeds and maximizes photosynthesis. A thicker crop encourages more competition, taller plants and possibly higher pods.
“We saw this last year for sure,” she said. “Cooler soils, delayed planting, the nodes tend to be closer to the ground so the pods have problems at harvest.”
Based on crop insurance data, the optimum time for planting soybeans is May 10 to 20. Normally soil temperatures are averaging at least 10 C at seeding depth by then, although that wasn’t so this year in most areas.
“At the fourth week of May we’re looking at 85 or 90 per cent yield potential,” Podolsky said. “And in the first week of June it will go down again.”
Later-seeded soybeans have as long as there’s enough heat during the growing season and frost doesn’t strike early.
The ideal soybean plant population ranges from 180,000 to 210,000 per acre, or about 40 plants per square metre, Elmer Kaskiw, Manitoba Agriculture, Food and Rural Development’s (MAFRD) farm production adviser at Minnedosa said May 21 during a webinar. However, research has shown fields cutting the population in half reduces yields by just 10 to 20 per cent. Soybeans will compensate by branching out producing more pods per branch and more seeds per pod.
Seeding rates also need to take into account seed germination and potential seed injury. Eighty per cent of the soybean seed sown with a planter survives on average, versus a 71 per cent survival rate using an air drill, Terry Buss, MAFRD’s farm production adviser at Beausejour said during a webinar May 22. Some planters achieve 90 per cent seed survival, he said.
Fertility is critical to soybean yield. Soybeans need 150 to 200 pounds of nitrogen per acre to produce a 30-bushel crop, Kaskiw said.
Some nitrogen will already be in the soil, while the soybean plant itself can make the rest, but only if a particular bacterium is in the soil. That’s why inoculating soybean seed is critical.
“We definitely recommend double inoculating,” Kaskiw said. “We feel it’s cheap insurance.”
Seed treatments are important for warding off seedling diseases and insects.
Bayer’s new Fluency agent has replaced talc because it reduces the dust from neonicotinoid seed insecticides linked to bee mortality. Kaskiw stressed adding the right amount and mixing it with the seed slowly.
“More is not better,” he said. “You shouldn’t have any application problems if you follow that procedure.”
Soybeans require 30 to 40 pounds of phosphorus per acre, ideally applied the year before. At seeding it should be side banded or placed an inch below the seed to avoid seed damage.
Soybeans require 30 to 60 pounds of potash per acre. Clay loam soils often have enough, but sandy soils can often be deficient. Soybeans also need 20 pounds of sulphur per acre.
Soybeans are not strong weed competitors, especially early in the growing, so early weed control is important, Nasir Shaikh, MAFRD’s weed specialist, said in an interview last week. Most soybeans are Roundup Ready, with glyphosate being the main herbicide used. However, Authority has just been registered for soybeans, providing a new residual weed control option and tool to delay the onset of glyphosate-tolerant weeds.
- More from the Manitoba Co-operator: Authority herbicides now registered for soybeans in Western Canada
Soybeans planted in stony fields should be “rolled” to push stones into the soil, which makes harvesting easier, Kaskiw said. Rolling wet soils can cause compaction.
Rolling as the crop emerges or at the first trifoliate stage can break plants. Kaskiw recommended rolling at the third trifoliate stage during the afternoon, when it’s warmer and the plants are more pliable.
Farmers should periodically check plants during the operation to ensure plants aren’t being heavily damaged.