Sunday, February 28, 2021

Snow Jobs: The white stuff makes for good growing

Where agriculture is concerned, dairy is king (or is dairy queen?) in northern NY State. Looking out the window now in late February, though, it looks like we should be growing snow peas or iceberg lettuce. Actually, for farmers, maple producers, foresters and gardeners, there is an up-side to having plenty of winter white stuff.

Snow has been called “the poor person’s fertilizer” because it’s a source of trace elements and more importantly, of plant-available forms of nitrogen, a nutrient often in short supply. When snowmelt releases a whole winter’s worth (i.e., almost six months) of nutrients in a short time, the nitrogen value can add up.

Since air is 78% nitrogen, you’d think plants would have all they needed. But atmospheric nitrogen, N2, is a very stable, inert molecule that plants are unable to use – you might say that for plants, nitrogen gas is broken. Fortunately, some soil bacteria can “fix” gaseous nitrogen, converting it to water-soluble forms that plants can slurp up. Lightning also turns nitrogen gas into plant “food.” But this only accounts for a small percentage of the nitrogen found in snow.

Turns out snow is a better fertilizer today than it was years ago. There’s an outfit called the National Atmospheric Deposition Program (NADP), which basically measures stuff that falls out of the sky that isn’t some form of water. According to the NADP, the vast majority of snow-borne nitrogen comes from pollution.

early 2016 Orda snowmakingMotor vehicles spew out various nitrous oxides, which are not great for us to breathe, but when washed into the soil, are nitrate fertilizers. Ammonia, another form of plant-available nitrogen, escapes from manure and commercial urea-based fertilizers, and is captured by water vapor which becomes snow.

So how much fertilizer is in the snowdrifts blanketing the North Country? Because we’re the “beneficiaries” of more pollution than most of the West and Midwest, we get more nitrogen in our snow than the national average, somewhere around 12 pounds per acre annually. Depending on the crop, a farmer may apply nitrogen on the order of 150 lbs. per acre, so 12 lbs. is small potatoes. Literally. But it’s not chopped liver, either (which is high in nitrogen but not an ideal soil amendment).

Snow-based nitrogen can be a significant boon to ecosystems on marginal soils. In a year with abundant snowfall, sugar bushes, timber lands and pastures undoubtedly benefit from “poor person’s fertilizer.” Snow also brings a fair bit of sulfur, which is an essential plant nutrient. It also can make soil more acidic, which can be good for the alkaline soils found in the eastern Lake Ontario-St. Lawrence area.

Obviously, snow provides soil moisture in early spring. What’s different about snowmelt as compared to rain is that snow releases water gradually enough that nearly all it gets into the soil. This gentle percolation is in contrast to summer rain, a percentage of which—sometimes a large portion—runs off and doesn’t benefit the soil.

When topsoil is saturated, or as agronomists put it, at field capacity, excess water seeps down through the soil profile. Eventually it becomes groundwater, raising the water table and recharging our aquifers. Nearly all water wells in the region tap into unconfined aquifers. This just means that the water that goes into the ground in a given location is the water that comes out of the well there. These aquifers depend on snowmelt, as well as prolonged heavy rains of spring and fall, for recharge.

Those who work in field and forest should take heart at the mounting snowbanks, not despair of them. Now if you’ll excuse me, I’ll be heading to the garden shortly with the rototiller to plow up some snow. Just as soon as I locate that envelope of Mixed Frozen Vegetables seeds…

Almanack file photos

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Paul Hetzler

Paul Hetzler has been an ISA Certified Arborist since 1996. His work has appeared in the medical journal The Lancet, as well as Highlights for Children Magazine.

You can read more of his work at PaulHetzlerNature.org or by picking up a copy of his book Shady Characters: Plant Vampires, Caterpillar Soup, Leprechaun Trees and Other Hilarities of the Natural World




4 Responses

  1. chris cohan says:

    I enjoyed the article. It was very informative. You write well and have a nice sense of humor, too.

  2. Todd Miller says:

    I also enjoyed learning about nitrogen in precipitation that is a source of small amounts of fertilizer to plants. I disagree with some your discussion on water infiltration through the soil, recharge, and aquifers, however. First, as long as the soil moisture threshold is satisfied, snowmelt and rain can infiltrate down through soil without the soil without having to be saturated. Field capacity (Cc) corresponds to the limit of available water and represents the moisture of the soil after drainage of the water contained in the macropores by gravity action. However, one has to be careful in describing “a saturated soil” because, if the soil is fully saturated and if the rate of precipitation exceeds the soil’s infiltration rate, then the excess water is rejected from the soil and is forced to flow as surface runoff rather than seeping down to recharge the groundwater system, whether an aquifer or non-aquifer. Also, I take issue concerning unconfined aquifers–in your statement “Nearly all water wells in the region tap into unconfined aquifers.” I disagree with that statement for the following reasons; 1) little is known about the types of aquifers (unconfined vs. confined) in the Adirondacks (there have been few studies), 2) since there are many post-glacial and former proglacial lakes in the Ads, there must be large amounts of fine-grained lake deposits in the many of the valleys and lowlands and, in which, these lake deposits would form confining beds, some of which would overlie confined aquifers (artesian aquifers), 3) many, if not most homeowner wells in the Ads, are probably finished in bedrock–where water-bearing fractures at depth are typically under confined conditions, and 4) glacial till (typically a confining unit) overlies and confines bedrock aquifers in large parts of the Ads.
    I agree that snowmelt melts slowly (most of the time) and seeps vertically downward to recharge the groundwater system, but it is important to point out, especially in areas underlain by fine-grained deposits such as till, that the fine-grained overburden often becomes fully saturated in the spring in many areas and the excess snowmelt and rain becomes rejected recharge that forms surface runoff that swells our rivers and lakes in early spring.
    I disagree with your statement “This gentle percolation (snowmelt) is in contrast to summer rain, a percentage of which—sometimes a large portion—runs off and doesn’t benefit the soil.” There is little groundwater recharge and runoff during the summer because evapotranspiration during the growing season, most of time, exceeds the rate of precipitation, therefore there is little GW and SW water runoff except during especially large or very intense storm events when rate of precipitation exceeds the evapotranspiration rate.

    • Wayne Miller says:

      Thank you for pointing out a number of issues with the author’s assertions. I would also point out that snow tends to melt before the frost is out of the grounds making the soil mostly impenetrable. This is especially true on open ground like farm fields.
      Also, the assertion that snow melts slowly is also less true on open ground. In fact, the existence of the Park is in no small part due to the speed of the spring melt and subsequent flooding runoff that were one result of the vast clear cutting of Adirondack forests. This followed the Civil War era development of the sulfide process for making paper from wood pulp. Repeated severe flooding in Troy and other riverfront cities, followed by low flow that impacted navigation during the summer months spurred New York City’ harbormaster, Theodore Roosevelt, to sign on to efforts to protect the northern forests and their watersheds.

      • Todd Miller says:

        Thanks for your comments. You make a good point that when the ground is frozen and forms an impermeable layer, there is rapid surface runoff during snowmelt. Also, that was an interesting historical perspective of effects that clear cutting had on hydrological conditions in the past. Another reason there is rapid surface runoff during snowmelt in that large parts of the Ads have no or little soil–relatively impermeable bedrock crops out at or near roughly 30-40% of land surface.

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