I’ve been thinking about snow and winter precipitation a lot this week as Georgia digs out from a record snowfall that hit the southern part of the state with amounts of up to 9 inches. This is the second snow event this winter, something that does not happen very often here, although I know it is much more common in many other parts of the country and the world. The heavy snow band stretched all the way from eastern Texas to eastern Virginia up the East Coast, bringing record snow amounts to many areas along the path, including a very heavy snowfall in New Orleans. In the past week I have seen references to snow as “poor man’s fertilizer” and I wondered where that came from and whether there was any truth to it. I discovered that it is a saying that is often used by farmers and even turned up in “Farmer Boy” by Laura Ingalls Wilder. The book tells the story of Laura’s husband, Almanzo, growing up on a farm in upstate New York in 1866. His father told him snow was a good thing and called it “poor man’s fertilizer.” We will explore what that means in this week’s Garden Professors blog.
Why is snow called “poor man’s fertilizer?”
Snow is sometimes called “poor man’s fertilizer” because, like rain, it can add nutrients to the soil when it falls and sinks into the ground. As snowflakes and rain droplets fall through the atmosphere they pick up trace minerals from dust particles and other nutrients like nitrogen compounds that are needed by plants as they grow. Lightning can also fix nitrogen in rain or snow, although the impacts are limited to areas right near the lightning strikes. The nitrogen compounds include nitrate, ammonium, and dissolved organic nitrogen. It is estimated that between 2 to 12 pounds of nitrogen are deposited per acre in the U.S. per year from rain and snow (at best about ½ pound/acre per inch of snow and usually much less than that). The highest amount of nutrients will occur in the first flush of rain or snow, since once they are washed out of the air, it takes a while for them to build back up.
Lightning contributes 5-10% of the nitrous oxide and the remainder comes from human activity such as emission from automobiles and industrial plants. Ammonium can make up 25-75% of the total N in precipitation and comes from soil microbial activity and manure and urea fertilizer outgassing. Since some of the nitrogen comes from human activity, it is probably no surprise that nitrogen levels in rain are higher in the eastern United States than they are out west due to the prevailing west-to-east winds over the continent. One of the results of this is too much nitrogen falling in some locations, enhancing crop yields but harming forests, waterways, and other natural landscapes.
The main benefit of the snowfall is the length of time it takes to melt, since that provides nitrogen to the soil over a longer period and reduces runoff. This is in contrast to rain, which often falls so fast that only a limited amount of the water can percolate into the soil. The rest runs off into streams and lakes resulting in more nitrogen there and less deposited into the ground. And of course snow is free so everyone that it reaches receives benefits at no cost compared to having to purchase and apply commercial fertilizers that add nitrogen to the soil, hence the reference to “poor man”.
What other benefits of snow cover are there?
In addition to providing moisture and nitrogen to the ground, the snow cover can provide other benefits to your gardens. The blanket of snow can provide an insulating layer between the very cold Arctic air that sometimes blows in from the north and the ground where plant roots and dormant plants are waiting out the winter months, as I discussed in November 2024. If the snow is high enough it can also provide some protection for tree trunks from the nibbles of hungry deer and rabbits looking for winter dining as well as protection for small rodents and other critters that are trying to avoid the eyes of hawks, owls, and foxes, who also need to eat.
Snowfall also serves as an important water source for many communities around the world, storing water in the snowpack in winter and slowly releasing it during the summer for use by communities and agricultural producers downstream. This is becoming a problem as more precipitation falls as rain instead of snow as the climate gets warmer because it changes the seasonal availability of the water. Meltwater from snow can also recharge the groundwater that can provide water through wells. The water from snow can also provide water for animals in winter, who may have limited sources of moisture to survive.
What limits are there to fertilization by snow?
Snow does not always provide much benefits to gardeners and farmers. If the ground is already frozen the meltwater may not be able to penetrate the surface and will run off before it can enhance soil nitrogen. If the soil is too permeable, the meltwater may sink down so deep that plants cannot reach the nutrients until later in the season when their roots stretch down to deeper levels, if at all. Even with a consistent snowpack over time, the amount of nitrogen that is able to infiltrate the soil is highly variable.
Enjoying the snow
While snow does provide some fertilizing effect due to the presence of nitrogen in the meltwater, the amount is not large. It’s highly variable due to the amount of dust picked up by the snowflakes as they fall through the atmosphere as well as how much and how fast the snow melts when it hits the ground. If the ground is frozen, very little may make it to the root zone. Testing your garden soil for nitrogen content each spring will allow you to determine how much nitrogen is already there and how much should be added using commercial fertilizers to provide the optimum levels for plant growth. But whether or not snow really is “poor man’s fertilizer”, it provides nourishment for the soul as you see this enjoyable and beautiful contrast to the greenness of your summer garden.
