Nitrogen is roughly 80% of our atmosphere and vital to plant growth. However, the industrial revolution increased nitrogen levels in our ecosystem, turning nitrogen gas into nitric acid. Nitric acid is a pollutant that acidifies terrestrial and aquatic ecosystems through Acid Rain. The increasing emission of pollutants, such as oxides of Sulphur and nitrogen, contained in power plant emissions, factory smoke and car exhausts, react with the moisture in the atmosphere creating acid rain. Many studies show that increased levels of nitric acid decrease soil biodiversity.
This experiment investigates the negative effects of Simulated acid aain on English pea (Pisum sativum) height, chlorophyll levels, harvest, and dry biomass. We predicted that simulated acid rain would significantly decrease harvest, height, chlorophyll levels and dry biomass weight. . Pea plants were grown in a garden setting, receiving ambient rain (control) and weekly simulated acid rain (pH of 2-6) treatments.
Results/Conclusions
Plants watered with a pH 2 or 3 developed brown spots and other morphological abnormalities. Plants treated with a pH 2 were shorter but not significantly different. Unfortunately, our harvest data was negatively affected by unplanned herbivory. It is important to note that peas from pH 2 were brittle and shorter. Height and chlorophyll levels were different between pH treatments, but were not significantly different. We were not surprised because previous trials had no significant relationship between pH and height, or between pH and chlorophyll levels.
The root biomass and pH was marginally significant (p= 0.055). English peas are legumes that rely on nitrogen fixing bacteria found in the soil. Other studies have shown that acid rain causes a decline in soil faunal diversity. It is possible the peas (and soil) watered with a pH of 2 or 3 were losing nitrogen fixing bacteria. Nitrogen fixing bacteria live in the root nodules causing the plants roots to weigh more because the nodules swell up, with a decline in nitrogen fixing bacteria indicating a decline in root weight. This study did not focus on the microbes in the soil. We recommend future studies test the soil microbe activity.
Overall, there were morphological changes when English peas were treated with a pH of 2 or 3. It was evident in the field, that nitrogen deposition was harming plant growth and development. Our results were shy of significance but suggest a strong influence of Acid Rain and nitrogen deposition on English pea growth and biomass.