A blanket of post-thaw snow is currently falling over parts of the Midwest from Oklahoma to the Great Lakes. A subscriber asked a question this morning as a joke, but a little research showed that there is nitrogen in snow. In fact, snows before or after the ground has thawed can yield some great benefits to your soil.
As precipitation falls through the atmosphere, it collects atmospheric nitrogen which is in the NH2 form. When snow collects on thawed soil, it slowly melts, allowing a slow-release of NH2 into the soil profile. Conversion to NH3 and nitrate fixing takes place without the microbial paralyzing effects of commercial anhydrous ammonia. Since the ground is already thawed, most of the moisture and nitrogen seep into the soil profile, adding to the total nitrogen content.
Heavy rains and lightning also contain atmospheric nitrogen, but rains heavy enough to contain measurable N generally runoff before nitrogen fixing can take place. Lightning also adds a little of its own, but in very localized pockets where strikes hit the ground.
Of the three, snow is the best form of natural nitrogen. Not only does it allow the necessary chemical reactions to take place in the soil, it also protects micronutrients and bacteria by blanketing the ground. Scientists and old school growers have observed a 5-10lbsN/acre addition from late spring or early fall snow events. This is only a benefit if the soil is not frozen. Most of the nitrogen laced snow that falls on frozen ground will be lost as runoff since the soil cannot soak it in.
So take heart if you are chaining up your loader tractor to move snow here on May 2. Atmospheric nitrogen tends to be high following a dry year suggesting there is N to be had in the snow today. Some will tell you that every cloud has a silver lining. In this case, every spring snow has a nitrogen lining.