Crop Comments: Sublimation, Right on Schedule
Occasionally the bottom drops out, temperature-wise, in Central New York during the last week of November. Three or four years ago, Thanksgiving Day in our area saw the mercury drop to -25º F. Fortunately, most places had already been blessed with at least a half-foot of protective snow, but it turned out that particular cold snap set the record for that entire year.
Normally, a record cold day might occur the first week of December … and that’s what happened this year. Although not the coldest day recorded this year in the Northeast, Dec. 5 shocked a lot of folks with temperatures plummeting toward (and reaching) -10º or lower.
Most of the time, what causes these severe cold snaps is the northern branch of the polar jet stream jutting south, allowing cold arctic air to follow. All the frost-sensitive plants were long dead, but such invasive cold snaps complement us if our fields and pastures have good ground cover – and chide us if they don’t. When the temperature drops this low (or just drops to or below -14º), sublimation takes place.
During sublimation, water in the form of ice or snow can evaporate at or below this temperature threshold without first having to go through the liquid phase. An accompanying benefit is that when air temperatures descend to this level, water vapor liberated from ice and snow rapidly forms low-hanging cloud cover. This helps seal in Earth’s warmth. Without this cloud shield, much of our planet’s geothermal heat would surge into the upper atmosphere due to radiational cooling.
Sublimation has some negative traits, however: bare soils, lacking cover crops, definitely freeze dry, meaning that the affected soils rapidly lose moisture. Also, dried soil particles – especially clays and silts loosened by freezing/thawing action – are vulnerable to wind and water erosion. The best way to dodge any threat to soil and moisture loss due to sublimation is to minimize the amount of time that soil lays bare and unprotected. The best way to harness the benefit of expanding ice – a critical part of freezing/thawing – is to determine the lime needs of the fields in question.
If your soil test results indicate the need for lime, the best time to apply it would be between when I write this column and when the next major snowfall arrives. The second-best time would be as soon after that snowfall that field conditions become passable.
In the coming weeks, there will be a lot of freezing/ thawing, an occurrence which increases the effective neutralizing value of liming material. Most commercial lime suppliers stress that lime spreads easier with air temperatures over 20º. If we do get some of those “warm” spells in the weeks ahead, let’s take advantage of them by “sweetening” soils that need it.
Mentioning dust once more, particularly on bare corn stubble ground, should you see these minute soil particles blowing around – maybe as part of a dust devil – commit to planting winter forage immediately following 2026’s corn silage harvest. Continuous freezing/ thawing tends to create potholes in roads during winter in regions like ours.
Because of its greater volume (thus lower density), ice floats. Thus, the visible part (the tip) of an iceberg is only about one-tenth of its mass. Once I accidentally conducted an experiment dealing with the freezing/expansion trait of seltzer in an unopened can. One frigid morning, I opened my truck’s door to see crystalline ice formations on the inside of the vehicle’s windshield. The truck’s defroster made light work of the ice crystals. Had the liquid been sugar-laden soda instead of seltzer, cleaning the windshield would have been much more of a challenge.
However, the natural sugars in many living plant species have their own antifreeze properties that enable them to survive cold in many situations. (Brassicas, like broccoli, cauliflower and cabbage, are good examples of such cold tolerance.)
by Paris Reidhead
