Frost damage can cause low test weight, quality issues, and yield loss in field crops
By Jackie Clark
Harvest season is underway in Ontario, and yesterday marked the first official day of fall. As summer came to a close, temperatures have been dipping low overnight, with some farmers in the province experiencing frost in their fields.
Frost damage in crops is “probably one of the hardest things to diagnose, because it takes a little while for the damage to show,” Dale Cowan, the agronomy strategy manager and a senior agronomist with AGRIS Co-operative Ltd. and Wanstead Farmers Co-operatives, told Farms.com.
Typically, signs of frost damage take three to four days to appear, he said. “You want to check your nighttime temperature to get some idea as to how cold it was.”
If the temperature drops down to freezing, or -1 C (30 F) “it’s going to do a little bit of damage to corn, maybe take some of the top leaves out, but it’s not hard enough to freeze the stalks,” he explained. To tell if a stalk was frozen, you can cut into one and see if the texture is mushy on the inside.
If only the leaves were frosted, “you’ll probably be OK,” Cowan said. However, “the plant may cannibalize sugars from the stalk because it’s filling the grain. That might lead to some standability issues later in the field.”
Light frost in corn may also lead to quality issues such as “lighter test weights, lower yields … higher moisture at harvest,” Cowan said. Frost slows down the drying process in the field.
The effect of frost “also depends on the growth stage. If you’re already black layered on corn, it’s no problem, you’re already mature. If you’re a week away from black layer, you’re probably going to end up with a lighter bushel weight,” he explained. “If soybeans were R7, which is a brown pod anywhere on the main stem, you’re probably going to be reasonably OK. You might be a 10 to 15 per cent yield loss. Anything prior to that, if the beans are green, it’s probably a pretty big loss.”
A hard frost in soybeans will lead to total crop loss. “If all the leaves have been frozen off and the plant’s got that limp, black-green colour to it, that’s how you know it’s been frozen,” he added. “Corn fields will start smelling like corn silage, and soybeans will start to get that sour smell in the field too.”
-2 C (28 F) for just 20 minutes is enough to kill both soybeans and corn this time of year, Cowan said.
“For corn, there’s an option to take corn silage” if there’s demand in your area, said Cowan. “You’re going to have to wait for the moisture to get down to the proper range before you do that.”
Hard frosts should be obvious for farmers to identify, he added. “It’s those partial cold nights where you might get some quality issues” or slight yield reduction.
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