This chart shows the dates, treatment number and varieties used in the soybean test plots:
MELFORT, Sask. — Soybean acres are expanding rapidly in Sask-atchewan but it’s still too early to draw definitive results from the field tests that have been carried out, said a crop physiologist.
Trials are underway at 10 locations across the province, Rosalind Bueckert from the University of Saskatchewan said July 26 during a joint annual field day hosted by the Northeast Agriculture Research Foundation and Agriculture Canada in Melfort.
About 100 producers, agrologists and students were toured through test plots during the day.
Bueckert spoke about relative maturity.
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“The aim of this kind of trial is for researchers to test, by trial and error, in a scientific way, which varieties are best suited to our region. This kind of test gives re-sults so we can advise farmers to grow the early-maturing varieties that have a stable response in a lot of years, so growers have lower risk in picking a variety and in growing a new crop.”
Soybeans rated as mature growth (MG) 4 and 5 are common in the soybean growing states of Missouri, Mississippi and Arkansas.
The lower the MG number, the better the variety is suited to northern production with long days of light in summer. In Ontario, growers usually choose MG 1, 2, and 0.
Because soybean flowering is controlled by short days and temperature, growing soybean in Sask-atchewan requires varieties from 1, 2, 0, 00, and 000.
Bueckert said these varieties are called day neutral or photoperiod insensitive, which means they don’t need short days to flower be-cause plant breeders have switched off the short-day requirement.
Instead, these soybean varieties can cope with Saskatchewan’s long days, but they need the right temperatures to develop, assuming they are not short of water.
“The (soybean) crop is actually configured the opposite way round as we would find our cereals,” she said.
“So if you show a soybean plant super long days, it really wants to see a super short day to flower. And so you end up with a very long vegetative stage. And finally, when we have super short days and it’s around September, it will go ‘great, I can now flower,’ and then the next day you have a killing frost.”
Because soybeans like 13 C temperatures and higher, varieties are classified by their life cycle length from seeding to crop maturity and by the overall temperature they react to, which uses a temperature calculation for the season.
The U.S. calculates this as the average daily temperature minus 13 and then adds this number for each day from seeding to maturity.
Canadian researchers borrow the heat units from corn heat unit calculations, which although different, describe the same sort of thing.
Saskatchewan varieties need to have a life cycle shorter than the frost-free period, which equals 112 days for Nipawin and 116 or 117 for Saskatoon.
Bueckert said the ideal variety would be one that would take 120 days or less to mature, preferably 110.
“It’s trying to get soybean to break that one minute mile.”
She said this 120 cut corresponds to varieties from MG 00 and 000 that require corn heat units ranging from 2,400 to 2,500.
“Definitely, you want a variety that has less than 2,400 corn heat units, 2,200 would be nice. In Sask-atchewan, you probably want a 00 or 000 variety, the 000 being the earliest when classified in their breeding programs (Manitoba and Ontario).
“There is also a number after the decimal, which is how much more delayed a variety is compared to the check variety of the MG. You can think of a 000.6 as being six days later flowering than the 000 check,” she said.
Because soybeans like water and heat, their yield increases during a hot, wet year and declines during a cool, dry year.
“Currently, yield ranges on production fields in Saskatchewan have ranged from crop failure, 15 bushels per acre to even 45 or 50 bu. per acre. When you have a mild drought before flowering, soybean shuts down to save water and this will delay flowering. If you get a mild drought during small pod formation, right after full flower, the crop can go on hold for two weeks, further delaying development,” she said.
“These complex reactions can then delay maturity, meaning the crop takes even more corn heat units to finish.”
She said high temperatures during pod filling will lower yields. Cold weather during flowering leads to fewer pods and lower yields, while a very early frost could delay maturity and cause immature pods, which can devastate a crop.
For first-time growers in Sask-atchewan, Bueckert recommended using a variety from MG 00 or 000.
She said it’s important to use the correct inoculant, which includes using two different inoculants of the Bradyrhizobium kind.
“It just can’t be pea inoculant. It has to be inoculant specific to soybean. There’s always a delay before you get nitrogen fixation, so you might want to consider starter nitrogen,” she said.
“If you have low soil test N, consider using a starter N at seeding because cold soils delay nodulation and you can starve the crop before biological nitrogen fixation from the inoculant is sufficient. Seed at 1.5 to two inches depth. Seed more than 25 plants per sq. metre, I would say 45 to 60. Seed when the ground temperature is above 13 C, at least above 10 C, to avoid stressed seedlings and poor stands. Stressed seedlings can be susceptible to sudden death syndrome, a seedling disease. Yellow crops may have iron deficiency chlorosis if on high pH soils (8).”
Bueckert said the trial in Melfort demonstrates that there may be little difference in a specific region between an MF 00 and an MF 000.
“The triple zeros are supposed to be better suited this far north, but they’re both day neutrals. Because there’s a lot of ways genetics can work, you potentially still need to have it run in a trial,” she said.
“The sky is the limit here. I think with climate change coming this is a new potential crop here in Melfort. If it doesn’t freeze.”
