The first week of December, Old Man Pre-Winter dumped two separate doses of snow over much of the Northeast. This clumpy snow doesn’t slide smoothly into my snowblower’s intake. My machine is a 15-year-old unit which my sons bought me, new … after I commented about “heart attack snow.” Snow falling between 30º and 35º becomes a lot of work, even with my 6.5 HP red machine.
When the temperature drops to 14º or lower, sublimation takes place. During sublimation, water in the form of ice or snow evaporates at or below this temperature threshold without first going through liquid phase. An associated 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 geothermal heat surges into upper atmosphere due to radiational cooling.
There’s a negative facet to sublimation: bare soils, lacking cover crop, definitely freeze-dry. This means affected soils 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 threats to soil and moisture loss from sublimation is to minimize the amount of time that soil lays bare and unprotected. One of the best steps toward harnessing the benefit of expanding ice – so common in freezing/thawing – is to determine the lime needs of fields.
If a soil needs lime (as verified by soil tests), the best time to apply it would be between when this column gets read and when a serious snowstorm falls – when the first blizzard arrives. Of course, folks just east of Lake Ontario have already been so “blizzarded” already.
The second-best time would be after the blizzard comes, if field conditions permit. In the next few weeks, there will be a lot of freezing/thawing, which increases the effective neutralizing value of liming materials. Most commercial lime spreaders stress that lime spreads easier with air temperatures over 20º. We should get some of those “warm” spells in the weeks ahead. Let’s plan to take advantage of them – if field conditions permit.
Freezing/thawing forces create road potholes during winter. Because of its greater volume, thus lower density, ice floats. The visible part of an iceberg is only about 15% of its mass. Once I accidentally conducted freezing experimentation with unopened cans of seltzer. I drink seltzer on the road to stay hydrated. Twelve winters ago, before starting my truck on a super-cold morning, upon opening the driver’s door, I observed pretty crystalline ice formations on the inside of the windshield. I’d left a full can of seltzer on the passenger seat; it had frozen. Evidently, just before it froze solid, a hairline crack formed in the can. The remaining liquid, under enormous pressure from expanding ice, atomized toward the windshield, freezing solidly into winter wonderland art patterns.
Attempting to not be beaten by whatever ice winter throws my way, I keep rock salt readily available to chase away ice that I can’t get with the snowblower – or even the snow shovel and push broom (using those last two items as seldom as possible). These tools move water; they do so by employing physical changes. But salt impacts water’s chemical behavior.
Most common salt is sodium chloride (NaCl, or table salt). Chemically, a salt is the end product of an acid reacting with a base. NaCl couples with water molecules, reacting with them, yielding two liquids: dilute hydrochloric acid (HCl) in solution and dilute sodium hydroxide (NaOH), also in solution. Dissolved, these compounds take up less volume than the original ice and the original dry salt. The remaining ice crystals restructure with a cracking sound.
Even without the addition of salt, water does pretty interesting things. With most compounds, as the liquid’s temperature liquid decreases, its density increases as its molecules become more closely packed. But this pattern does not hold true for ice being formed from liquid water; the exact opposite occurs. This is because in liquid water, each water molecule is hydrogen-bonded, on average, to 3.4 other water molecules. In ice, each molecule is hydrogen-bonded to four other molecules in a very precise lattice-type structure – similar to the jacks some of us older people played with as children. This means that 100 grams of water at 34º has a volume of 100 milliliters (ml). When that 100 grams of water becomes ice at 32º, it now occupies 117 ml of volume (4.0/3.4 x 100). With limited space, that’s pretty serious crowding amongst water molecules. Such crowding causes enough force to break rigid containers like water lines, engine blocks and unopened cans of seltzer.
We’ve harnessed salt to improve our luck with winter. Let’s harness winter to improve ruminant diets. Livestock nutritionists refer to heat increment (HI) to note the energy losses associated with digesting food. HI-based energy losses are greater with fibrous foods, like roughages, than with grain and less fibrous concentrates. According to my primary Cornell Animal Science Nutrition textbook, “About 33% of the nutrients ingested in corn grain are used in the work of digestion, while this loss is approximately 60% in the case of wheat straw.”
These extreme examples of different feedstuffs help us visualize how mammals with different digestive systems, one created to process vegetative (fibrous) materials rather than seeds, crank out a lot of heat. Cattle, sheep and goats benefit from fiber-based HI in cold weather to keep warm, as do deer. That frees up the higher quality, less fibrous feeds for other functions, like making milk and muscle.
Back to sublimation: While water changing from liquid to solid ice expands, ice getting colder (down to 14º or less) contracts enough to pop off some water molecules. Those liberated molecules jump straight from solid form to gaseous form. So fields without ground cover, getting colder, tend to lose even more water.
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