If soil temperatures are cool plant cereals and field peas first, says Manitoba Agriculture Farm Production Advisor Lionel Kaskiw, based in Souris.
Soil temperatures are warming, but are still variable depending on soil type and location, he said during the Westman Crop Talk webinar May. 1.
Soil temperature readings are available at 109 Manitoba Agriculture weather stations across agro-Manitoba on the Manitoba Agriculture website.
Field peas will geminate at 4 C, while cereals will do the same at 5 or 6 C, Kaskiw said
Field peas and cereals also tolerate frost better than some crops because their growing points early on are below the soil surface, he said.
Soil temperatures in the Westman region this week varied from 5.1 to 10.7 C at five centimetres, Kaskiw said.
The most accurate way to assess soil temperature is to average readings taken in the morning and early evening, he said.
Ideally soil temperatures should be 10 C for canola seeding, Kaskiw said. Canola seeded into 2 and 3 C soil will take seven to eight and five to six days to emerge, respectively, Kaskiw said. Delayed emergence not only weakens the canola crop, it makes it more vulnerable to flea beetle damage.
“The day you put the (canola) seed in the ground is the day the clock starts ticking on that seed treatment,” he said. “If the plant doesn’t come up for seven to 10 days you’ve already lost seven to 10 days of (flea beetle) control on that seed.”
Early seeded canola is a bit more susceptible to frost injury should temperatures drop, Kaskiw said.
“If you do get it up and growing in cool conditions — that cotyledon stage is critical for canola —it can get some frost damage,” he said. “We’ve seen that in several years. It will come back. It can handle the frost, but it will set it back a fair bit.”
While there are risks, early seeding also has many benefits, including potentially higher yields, Kaskiw said. Early crops can take advantage of what moisture is there, which in many areas is less than normal following a dry 2017 growing season, below normal snowfall and one of the driest Aprils on record.
Early crops can get a jump on weeds, insects and may avoid heat stress, Kaskiw said.
To mitigate the affect of seeding in cold soils farmers can treat their seed to ward off seedling diseases and up the seeding rate to offset potential seed or seedling mortality, he said.
Farmers should also avoid placing too much nitrogen with the seed to avoid seedling damage and not seed too deeply, which is tempting when soils are dry.
“The longer that seed sits in the ground the more energy it loses,” Kaskiw said. “We had this last year or two years ago when some producers were trying to seed to moisture. We had a very uneven germination that year. We didn’t get rain until the third or fourth week of May and then later on we had a second growth… and very uneven crops.
“Try not to go too deep. That is one thing we seem to struggle with every year.”