GARDENING: True or false – Lightning promotes greener lawn growth
Free Press Gardening Columnist
The rains have been very good to our lawns and landscape plantings. Even the lightning has been beneficial, converting some of the nitrogen in the air into nitrogen our plants can use.
The energy of a lightning bolt heats the column of air through which the lightning passes. When the lightning-channel air cools, it causes nitrogen gas to combine with oxygen and form nitrogen oxides (NO and NO2). These oxides are carried into the soil by rain where they can be converted by bacteria into NO3 and absorbed by plant roots. NO2 is toxic to roots so bacteria are necessary to change it to a form plants can use, NO3. So if you have ever wondered why your lawn is much greener after a lightning storm than before, you now have your answer.
A question I am sometimes asked when people realize lightning is involved in “fertilizing” their lawn is how much nitrogen oxide can lightning create? Hill, Rinker, and Willson at the University of California provided the answer. They found the maximum global production rate of nitrogen oxides by lightning is about six quadrilliard molecules per second (that’s six followed by 27 zeros), or more than 14 million tons of NO2 per year.
According to figures provided by the U.S. Department of Agriculture, the United States used slightly less than 13 million tons of nitrogen in 2011, with almost half being used to grow corn. More lightning, if it could be controlled, would be a benefit. After all 78 percent of our air is nitrogen so there is a lot of nitrogen available to convert.
There are times when extra root-available nitrogen at this time of year is more of a detriment than a benefit. Trees and shrubs suffering from lack of water can be stimulated into growth by nitrogen, resulting in those plants pushing leaves. When buds of our woody landscape plants break and start to grow at this time of year the plant often does not have time to develop another set of buds for the following year. In addition the new growth may not have time to shut down for winter weather and is consequently killed when freezing weather arrives. If the lightning occurs after the trees and shrubs start to shut down, or you fertilize your lawn after about mid-October, the additional nitrogen should not cause your trees and shrubs to pop growth yet this fall.
The fertilizers we apply to our soil, whether organic or synthetic, are salts. If the salt level is excessive for the plant, moisture will be pulled out of its roots causing it to wilt, develop brown tips on its leaves, and sometimes even die. When fertilizer is applied to moist soil, the fertilizer is diluted helping to buffer the dehydrating effects of the salt. Even when a liquid fertilizer is applied, the soil should be moist prior to applying the fertilizer.
If the soil was moist when you fertilized and the plant wilts within a day or two of fertilizing, there is a good chance you applied too much fertilizer and increased the soluble salt level in the soil to a level higher than the roots can tolerate. When you make this mistake you might be able to fix the problem by leaching the salts out of the soil. If the troubled plant is a houseplant, place it in the shower or sink and run tepid water through the soil. The water should be applied slow enough to penetrate the soil without forming a puddle on the surface. Fifteen or 20 minutes of this treatment just might save your plant.
Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at Curtis.Swift@alumni.colostate.edu, 970-778-7866 or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.
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