How does biological nitrogen (N) fixation enhance grain crops? Nitrogen (N2), a vital building block of proteins and DNA, is abundant in the atmosphere (78%). However, plants can only access limited reserves of inorganic nitrogen in the soil, primarily nitrate and ammonium. There are three primary sources of this nutrient. The first is cyclical and natural, where plants reuse N from the organic compounds of decomposing organisms. The second, and most detrimental, is the application of fertilizers to agricultural crops. The third, which is the focus of our study, is biological fixation. In this process, bacteria convert N2 into ammonium. Bacteria have been fixing atmospheric nitrogen for hundreds of millions of years, contributing significantly to the nitrogen input in natural systems. These bacteria capture the gas, attach to plant roots, and fix the N, transforming it into a form the plant can use, promoting plant growth. In our project, we aim to compare the microbial activity in corn crops with that of native Atlantic rainforest fields. Little is known about how these plants absorb this N. We intend to determine if there are fixing microorganisms and quantify how much of this N is actually utilized by the plant. The answers to these questions could potentially contribute to the biological fertilization of these crops in the future, similar to what is currently done with soybeans.