Much of Manitoba’s soybean crop is mature enough to survive the sub-zero temperatures expected this week, although yields and quality could be reduced in some areas, a soybean expert said Sept. 8.
“Ideally two weeks without frost would be wonderful,” Dennis Lange, a farm production adviser with Manitoba Agriculture, Food and Rural Development (MAFRD) said in an interview Sept. 8. “If we got frost at the end of this week I bet you a lot of the beans in the Red River Valley would be getting fairly close to R-8.”
The R-8 stage is when 95 per cent of soybean pods have reached their mature colour and can survive a frost with little or no ill effects.
Once hitting R-8 soybeans can usually be combined 10 to 14 days later.
However, soybeans are not as advanced in western Manitoba and therefore more at risk if it freezes this week.
As of Monday many soybeans in western Manitoba were in the mid-R-6 to early-R-7 stage, Lange said after consulting some of his MAFRD colleagues.
Soybeans hit by frost in the R-5 and R-6 stage could see a 50 to 70 per cent and 20 to 30 per cent cut in yield, Lange said.
Lange has stressed for years the importance of selecting a soybean with the right maturity for the area it is grown in. Farmers in western Manitoba should plant early-maturing varieties, and it appears they are based on crop insurance data, he said.
Farmers in the Red River Valley, where it’s usually warmer, can grow mid- and later-maturing varieties.
As of Monday, Environment Canada was forecasting lows in western Manitoba of zero and -2 for early Thursday and Friday morning. Lows in south-central regions were predicted to remain above zero, but just barely.
At the R-7 stage a killing frost (-2 or colder) will cut soybean yields by around five per cent, Lange said. However, frost then will also result in more green seeds, a lower grade and less return, he added.
Traditionally frost strikes much of the province by mid-September, but for the last three or four years, the frost-free period has continued until late September, and in some areas, into early October. And during several of those years the soybeans and corn needed that extra time to fully mature.
Manitoba farmers planted a record 1.3 million acres of soybeans this spring and they might have seeded more had it not been so wet in much of western Manitoba, Lange said.
Even if the soybean crop is fully mature before it freezes, Lange predicts an average provincial yield in the low 30-bushel-an-acre range, which would be close to the 10-year average of 31.
Although most of agro-Manitoba received higher-than-average rainfall between May 1 and Sept. 1 a lot of it came early. Much of the crop needed rain during the seed development stage in August, he said.
Most of Manitoba has been slightly cooler than normal too.
“Yields are dictated a lot by the season and when the rains came and the amount of heat we had,” Lange said.
Last year Manitoba farmers seeded a million acres of soybeans and harvested a record average yield of 38 bushels an acre.
“Last year the earliest variety hit 95 per cent brown pod on the September long weekend,” Lange said. “That same variety this year, I had one plot in Carman hit that just the other day, but the other varieties are slowly coming along. Another good week would be very beneficial and two weeks would be even better.”
Lange reckons most soybeans in western Manitoba are more advanced than the same time last year due to a lack of rain in August.
Information about variety maturity is available in Seed Manitoba, he said. Following the system used in Ontario and the United States, seed companies introduced a numbering system to indicate maturity. Early-maturing varieties range from 000 to 00.3, mid-range types are 00.4 to 00.6 and later maturing varieties are 00.7 to 00.9.
Lange also suggests farmers note the maturity of soybeans growing in their area to help with future variety selection. Some companies post the name of their variety by field sides. To make a proper assessment one should know when the crop was seeded, he added.