A professional forester once explained to me how snow loads can seriously harm trees: “The pressure from above is simply too great. Such breakdowns mostly happen in the months of March and April, when the snow is transformed from feather-light fluff to dead weight.” He estimates the point at which snow becomes dangerous by analyzing the clusters of falling flakes. He said when the clusters are about the same diameter as a quarter, the tree safety situation becomes critical. This snowflake physical condition is a trait of wet snow, which holds a lot of water and is very sticky. Rather than falling through the tree branches, such wet snow adheres to them, piling up in thick, heavy layers.
Wet snow falling on tall, sturdy trees can break branches, but the problem is even worse on immature trees. With lanky trunks and small crowns, they are either broken by snow loads or bent over so far that they never right themselves. Much smaller trees, including saplings, are usually supple enough to rebound from snow piling up on their tiny branches. Around the first day of spring, much of the Northeast experienced some heavy snow, with air temperatures seemingly locked in at the freezing point. A lot of branches weakened on trees in our yard, both coniferous and deciduous. Some branches did break off (fortunately, no big ones).
Some refer to this dense, soggy gift of nature as “heart attack snow.” But it still offers some pluses, as old timers often refer to this spring snow as “Poor Man’s Fertilizer.” This is because snow, like rain, contains nitrogen (N), as well as minute (but measurable) amounts of phosphorus (P) and sulfur (S). The wetter snow washes these elements out of the atmosphere, depositing them on our fields, yards and gardens. Research has shown that the airborne presence of these plant nutrients has been increased by byproducts of industrialization – namely, emissions. Still, these are plant nutrients, and, importantly they are free to crop growers.
The amount of S in the atmosphere has decreased in recent years, due mostly to the effectiveness of the federal Clean Air Act. Earth’s atmosphere is roughly 78% N, but that N is relatively insoluble in its couplet (N2) form. Pollutants like nitrous oxide (a greenhouse gas) merge much more readily with snow, and even water, than does S. According to scientific field tests, the amount of N that accompanies precipitation each year ranges between two and 12 pounds per acre – with an average value of seven pounds being presumed for soil nutrient calculations. Scientists believe that snowflakes pick up more N than raindrops, because snowflakes are more crystalline in structure than water. Thus, they are expected to combine more readily with airborne chemicals.
How much N per acre we actually get from snowfall depends on our location and our annual snow accumulation. An average annual N deposit of seven pounds doesn’t seem like much compared to commercial N applications exceeding 100 pounds (commonly dosed on each acre of corn). But the key word is “free,” making this source of N a pleasant side benefit, assuming not too many tree branches get broken. While rain and lightning also contain N, snow boasts several agronomic advantages over the other two free sources. First, snow stays around for a while, setting free its nutrients in a slow-release manner. Also, snow helps insulate plants from fluctuations in temperature, which can cause heaving and related problems from frequent freezing and thawing. Thirdly, snow makes small plants such as strawberries less visible to hungry critters. Fourthly, snow helps prevent plant growth from starting too early. Lastly, snow, unlike heavy rainfall, doesn’t leach nutrients away from plant roots.
Residents of Canada’s Maritime provinces (which many consider an extension of our Northeast) divide their spring snowfalls into three categories. First comes the “Robin’s Snow,” occurring just after the robins migrate back. Then the “Smelt Snow” happens when the smelt are “running” in the rivers near the coast. Lastly, these Canadians recognize “Poor Man’s Fertilizer,” delivered by the snow that lands on freshly plowed land in early spring. But the economic benefit of snow-borne free N becomes even more pronounced when framed by the chaotic crop nutrient supply/demand situation presently confronting growers. One of the fertilizer industry periodicals that I monitor closely is the Argus North America Fertilizer Newsletter, published twice monthly. Fertilizer ingredient commodity prices are listed for about a dozen distribution points in the U.S. One servicing growers in the Northeast is Cincinnati. I’ll give per ton costs for urea and ammonium nitrate, FOB Cincinnati for Feb. 24, 2022. The N levels on the two commodities are 45% and 33.5%, respectively. Average prices on that date, at that location, were $915/ton and $700/ton, respectively. This means that one pound of N in urea costs $1.02, and one pound of N in ammonium nitrate costs $0.96. That makes each of those pounds of snow N worth about a dollar. Both of those fertilizer ingredient commodity prices have increased about 200% since March 4, 2020.
My take-home message has several parts. First, figure how much fertilizer you can afford – accepting the fact that your fertilizer dollar will go less than half as far as was the case 25 months ago. Get that fertilizer ordered. If you haven’t already done so in the last three years, get your soils sampled so you can cut back on application rates with precision. Use nature’s contribution as part of the cake, not just the frosting. Use lime by recommendation, accepting that its price increases have been comparatively negligible. And lastly, increase the amount of perennial legumes in your rotations. Typically, their N-fixing bacteria colonies pocket about 10 times as much N as what nature piggybacks on her spring snowflakes.