Kudzu (Pueraria montana, formerly lobata) is a legume which can ‘fix’ nitrogen in the soil. Kudzu was brought from Asia to the U.S. to feed animals and as a Chinese and Japanese herbal medicine. The plant grew well in the southeast part of this country and has become wildly invasive, covering much of the southeastern U.S. Kudzu covers more area in the southeastern United States than do soybeans.
Adequate studies of the atmospheric and environmental impact of invasive plants have not been done. Nitrogen dioxide (NO2) and nitric oxide (NO) are the prime precursors of ozone. Because of the increased nitrogen in the soils and increased NO release by the soils caused by the kudzu plant, kudzu has the ability to raise ozone atmospheric levels. Nitrous oxide (N2O) is formed, too, which has the ability to impact local air quality.
The authors studied kudzu and soils in Madison County, Georgia, in 2007. Because of kudzu, soil emissions of NO were increased by 100%. “High ozone events” occur when the levels of ozone are more than 70 ppb and these events occur about 10 to 20 days each year. Kudzu has resulted in an increase in the number of high ozone events by 7 days per summer.
NO emissions in the U.S. were reduced by 33% by reductions of roadway emissions and fuel combustion from 1990 to 2007. This could be reversed by the kudzu emissions. Kudzu emissions can cause soil acidification, increase aluminum mobilization and increase nitrate drainage into water ecosystems. Kudzu is likely to spread more rapidly with increasing atmospheric CO2 from global warming. Areas where little fertilizer is used are best for kudzu growth.
The Environmental Protection Agency is considering changing the threshold level of ozone from 70 ppb to between 60 and 70 ppb.
CONCLUSION: Kudzu invasion causes ozone formation and has the potential to overcome some of the progress made in control of atmospheric ozone in the past. The kudzu plant has been found in Maine and Washington States.
NOTE: Read a Kudzu review.
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