The long stretch of cooler-than-normal temperatures came up often as farmers visited during the Manitoba Pulse Growers Association (MPGA) tour Aug. 8.
Most soybean and edible bean crops look good around the province, but growers want hotter temperatures to ensure the heat-loving crops mature before the first killing frost this fall.
MAFRI’s weekly weather data shows most stations received close to the normal number of corn heat units as of July 29.
Conditions can quickly turn. Dennis Lange, a farm production adviser with Manitoba Agriculture, Food and Rural Initiatives in Altona, said in 2011 July and most of August were cold, but hot weather in late August and September saved the day.
“Those last three weeks made a lot of beans,” he said.
Brandon-based Agriculture and Agri-Food Canada (AAFC) researcher Aaron Glenn is investigating how accurately corn heat units indicate how much time a soybean variety will take to mature. Day length might play a bigger role in soybean maturity than first thought, said MPGA agronomist Kristen Podolsky.
“This could explain how we are able to expand the soybean acres into those (more northern) areas — Ste. Rose, Roblin — they’re actually being tested at The Pas this year,” she said. “We’re really trying to pinpoint the growth and maturity of soybeans and how much is related to heat units as opposed to day length, especially in this new environment. It’s different than places like North Dakota, Minnesota and Ontario that have different day lengths.”
Lange said growing a soybean that matures before the first normal killing frost is important, as is taking moisture into account, because it affects soybean maturity.
“If it’s a drier year the beans will mature earlier and if you have more moisture they’ll take a bit longer to mature,” he said. “Keep in mind if you plant May 15 and it takes 117 days, that’s Sept. 10. If you plant on May 15 and you have 130 days, that’s a lot longer.”
Don’t forget P
Soybean fertility is being researched by the University of Manitoba and MAFRI, Podolsky said. Soybeans, which are annual legumes, produce 75 per cent of the nitrogen they need. At this stage they’re making about 4.5 pounds per acre per day. That’s why inoculation is so important — to ensure those nitrogen-fixing nodules are present and working.
But with the crop taking care of its own nitrogen, farmers sometimes forget about the other nutrients.
Soybeans require a lot of phosphorus. But the risk of damaging the seed limits how much can be applied at seeding time.
“Farmers need to make sure they’re getting lots of P on the crops that they can — winter wheat, spring wheat, cereals,” MAFRI farm production adviser Ingrid Kristjanson said later in an interview. “Some are actually banding it in the fall so they get enough phosphorus on because they can’t put it on with their seeding equipment. It’s becoming a big issue with some guys.”
Soybean plant populations and row spacings are also being studied. Previous work has shown little difference in yield between solid seeding and rows. However, the latter requires less seed, which saves the farmer money.
Usually the planting system depends on what equipment the farmer already has, said AAFC technician Mark Sandercock.
Lange recommends aiming for 200,000 plants per acre when solid seeding soybeans. Fewer plants might yield as well but a higher population is better for competing with the weeds.
Bob Connor, a Morden-based AAFC plant pathologist, is screening various edible bean cultivars for natural resistance to root diseases.
“We were surprised and found a couple of cranberry varieties with very good resistance — the best resistance of anything we saw in our studies,” he said.
The hope is to transfer that resistance to other large-seeded types of edible beans.
Root diseases aren’t a problem in Manitoba soybeans right now, but that could change, Connor said.
“We know root diseases can build up over time, especially if we get a large acreage and the crop is grown on the same field with fairly short rotations,” he said.
Phytophthora, a potentially yield-robbing soybean root disease, hasn’t been found in Manitoba yet, although it is present in North Dakota. The best way to avoid the disease is growing soybeans on a three-year rotation, Connor said.