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Tori Mattmiller – Southwest Arkansas Regional Science Fair Winner Southern Arkansas University, Magnolia, AR

Tori Mattmiller, Emerson High School, Emerson, AR

Mentor: Connie Orsak

Category: Agriculture, Earth and Environmental Sciences

Project Title: The Effect of Acid Rain on Soybean Root Modules



Farmers have started using rhizobia bacteria-based inoculants to fertilize their soybeans. The rhizobia bacteria create a symbiosis relationship with the legume causing root nodules on the plant.

Tori Mattmiller

In Arkansas, most of the farmland used to grow crops has acidic soil. Could the acidic soil have an effect on the symbiosis relationship the bacteria and plant have? Can a low pH balance caused by acid rain affect the amount of soybean root nodules? It was determined that a low pH balance could ultimately decrease the amount of root nodules on the soybean. To test this theory, the soybeans were grown using inoculants (rhizobia bacteria); half of the plants were watered with distilled water (control group) while the other half were watered with acidic rain solution (manipulated).


After three weeks the plants were taken out of the soil (roots intact), the soybeans were tested by how much area the nodules took up on graph paper. The data proved that low pH balance caused by acid rain decreases the amount of soybean root nodules. The control group had an average area of 8.3% occupied by root nodules; the manipulated group had an average of 4.1% occupied by root nodules. The experiment supported the claim that a low pH balance causes less soybean root nodules. The data found during this experiment can be used to help farmers make intelligent decisions when it comes to using rhizobia bacteria inoculant to fertilize their acidic soil.

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