Acid rain affects plants directly and decreases soil quality to reduce yields from agriculture. Its effects are particularly severe in locations near sources of sulfur dioxide and nitrogen oxides. In the United States, about two-thirds of sulfur dioxide and one-quarter of nitrogen oxides come from power generation plants burning fossil fuels, while the rest is from industrial and transportation sources.
Acid rain comes from chemical reactions in the atmosphere among oxygen, water and sulfur or nitrogen oxides. When sulfur dioxide dissolves in small droplets of water in clouds, it reacts with the hydrogen and oxygen of the water to form a weak solution of sulfuric acid. Similarly, nitrogen oxides form weak nitric acid in water droplets. The clouds can drift over hundreds of miles carrying their acid droplets. When conditions are right for rain, the droplets grow and fall to the ground. In many areas of the United States, such as the great plains, the acid rain falls mostly on land used for agriculture.
Acid rain influences both the quality and yield of agricultural products. Acid rain can damage the leaves of vegetables such as spinach and cause blemishes on delicate products such as tomatoes. The production and quality of root vegetables is reduced. The damage depends on the strength of the acids in the acid rain and the frequency with which the crops are exposed. In addition to cosmetic damage, there is the possibility that crops grown under acidic conditions have lower nutritional value with fewer minerals.
The acidic nature of acid rain leaches plant nutrients out of the soil and can make it less productive for agriculture. Soils with high alkaline content, such as those containing calcium carbonate or limestone, can neutralize the acids and are less sensitive. Other soils normally contain the minerals that plants need, but the acid in acid rain dissolves them and replaces the metallic ions with hydrogen. When the plants absorb water that normally contains the minerals, they get hydrogen instead and can't grow as large or as quickly as before. In severe cases, this lack of minerals can kill the plants.
The U.S. Environmental Protection Agency has taken steps to reduce emissions of sulfur dioxide and nitrogen oxides and continues to monitor these pollutants. Car manufacturers are required to produce cars that emit less of these damaging gases and power plants have to install filters to reduce emissions. As an individual, you can reduce your use of electric power and make sure that the catalytic converter on your car is working properly. Smaller cars and cars with smaller engines produce less carbon dioxide. Insulating your home, using efficient heating and cooling systems and avoiding heating with oil can make a substantial contribution to reducing the effects of acid rain on agriculture.