Some of you may have heard that a thunderstorm results in greener grass. That may or may not be exactly true since much of the green likely comes from water helping the plant grow. It is true though that a storm’s electrical display contributes to plant nutrition and helps to some degree with the growth of grass. The connection might seem hard to grasp – what does a flash of lightning contribute to the health of grass? – but it’s actually fairly straightforward, and an example of one of the planet’s fundamental, life-sustaining physical cycles.
Nitrogen is an essential nutrient for plants and other organisms, being a fundamental part of nucleic acids, amino acids and proteins, not to mention the photosynthesizing plant pigment called chlorophyll. It’s also the single most abundant gas in the Earth’s atmosphere, accounting for about 78 percent of its composition. (Oxygen is the second-most abundant atmospheric gas, at about 20 percent.)
Despite that abundance, atmospheric nitrogen (N2) isn’t readily available to most lifeforms with the exception of blue-green algae, some free living soil bacteria and rhizobia bacteria in nodules of legume roots. All other organisms require nitrogen to be transformed, or “fixed,” into more reactive compounds such as nitrates (NO3) or ammonia (NH3) before they can use it for biological growth and processes.
The process by which nitrogen is converted into a usable form is called nitrogen fixation. Rhizobia bacteria are by far the most significant source of biological nitrogen fixation. Atmospheric fixation is another way nitrogen gas can be transformed into nitrates and ammonia. Humans also artificially accomplish nitrogen fixation in the industrial production of fertilizers but nature does this for free through lightning.
The tremendous heat released by a bolt of lightning – some 50,000 degrees Fahrenheit, roughly five times the temperature of the sun’s surface – can split apart a nitrogen molecule to free up two nitrogen atoms. A liberated nitrogen atom can then bond with oxygen atoms to form nitrogen oxides that, dissolving into raindrops, become nitrates. The lightning-freed nitrogen may also bond with atmospheric hydrogen to form ammonia. These soluble nitrogen compounds then fall to the Earth in rainfall, providing a natural, lightning-produced fertilizer for grass and other plants.
When you consider that some 40 lightning bolts flash over the (mighty stormy) Earth every second, you get a sense for the significance of this atmospheric nitrogen fixation, even if it’s overall less important than biological fixation. It’s been estimated that lightning produces roughly 13,000 tons of nitrates each day around the globe. Now before you stop planting legumes or stop applying N fertilizer, remember that 13,000 tons spread around the globe every day equals only about 10 lbs/acre per year on your farm in Kentucky via lightning.
There’s no question that lightning provides a source of nitrogen useful for growing grass. Heavy downpours from a thunderstorm may also simply wash dust off grass leaves, resulting in greener grass. ~ adapted from article by Ethan Shaw, Sciencing.com, Sept. 2021.