It can be tempting to plant as early as possible in the spring, but producers should be particularly careful with soybeans, says a Manitoba Agriculture bean expert.
“Folks want to get going, (and) patience, patience, patience is a hard thing to preach to people, but you really do need patience (with soybeans),” Terry Buss, a crop production adviser in Beausejour, told a recent Canola Council of Canada CanoLab meeting.
“Of all our major field crops in Western Canada, early seeding generally shows yield increase…. (But) soybeans are the one that requires some of the finer management (for seeding dates).”
Planting soybeans early is attractive because it potentially provides more time for plant growth in the spring. Plants with more nodes on the stem can produce more flowers and more pods.
“The bigger the plant is before we go (to) reproductive (phase) in June… the better the yield potential of that plant,” Buss said.
Most agronomists recommend seeding soybeans in the second or third week of May, but some producers have been ignoring that rule. Buss said growers around Beausejour have planted beans around April 20.
“I never tell people when to plant their beans…. What I would ask them to do is get in touch with the key risk factors,” he said. “One of the things driving this interest in early seeding … is the fact that people have gotten away with it.”
The major risks of early seeding include spring frost, slow emergence and cold water in the soil.
“My biggest worry for early seeding is the frost,” Buss said.
Frost can damage beans if temperatures drop to – 1.2 to 1.8 C.
“Soybeans bring the growing point above the ground when they emerge,” Buss said.
“They can tolerate some frost t… but they’re not as flexible as some of the other crops that we grow.”
Planting in late April can also increase the amount of time it takes for the plant to emerge, which can compromise seed and plant health.
“We had some beans that took 30 days to get out of the ground (last year),” Buss said.
“Those beans are not as healthy as ones that emerged quickly.”
Soybeans are also sensitive to chilly soil moisture. Water around a seed can potentially kill it if the temperature drops below 4.5 C.
Early soybean seeding can be risky, but data shows that late seeding is a bigger mistake.
Manitoba Agricultural Services Corp. statistics show that yield potential is still 100 percent when the crop is seeded in the third week of May, but it drops by 15 to 20 percent when seeded the first week of June.
“If you want to get (consistently) low yields in soybeans, always plant really late,” Buss said.