Journal of Geoscience and Environment Protection, 2020, 8, 143-154 https://www.scirp.org/journal/gep ISSN Online: 2327-4344 ISSN Print: 2327-4336 Tile-Drain and Denitrification Bioreactor Water Chemistry for a Soybean (Glycine max (L.) Merr.)-Corn (Zea mays L.) Rotation in East-Central Missouri (USA) Michael Aide * , Indi Braden # , David Mauk, Robert W. McAlister, Byron McVay, Susan Murray, Samantha Siemers, Sven Svenson, Julie Weathers Department of Agriculture, Southeast Missouri State University, Cape Girardeau, Missouri, USA Abstract Nitrogen transport from agriculture production fields raises the specter of en- vironmental degradation of freshwater resources. Our objectives were to doc- ument and evaluate nitrate-N, ammonium-N, phosphorus and other nutrients emanating from a 40-ha controlled subsurface irrigation drainage technology coupled in series with a denitrification bioreactor. The intent of the denitrifi- cation bioreactor is to create an environment for anoxic microbial populations to support denitrification. We monitored the tile-drainage effluent and deni- trification bioreactor water chemistry under a corn-soybean rotation to esti- mate the nutrient concentrations and the competence of the denitrification bioreactor to foster denitrification. Nitrate-N bearing tile drainage effluents ranged from less than 1.5 to 109 mg NO 3 -N/L, with the nitrate concentration differences attributed primarily to the: 1) timing of nitrogen fertilization for corn, 2) soil mineralization and residue decomposition, and 3) intense rainfall events. The denitrification bioreactor was highly effective in reducing drai- nage water nitrate-N concentrations providing the rate of water flow through the denitrification bioreactor permitted sufficient time for equilibrium to be attained for the nitrate reduction reactions. The nitrate-N concentrations en- tering the denitrification bioreactor ranged from 0.4 to 103 mg NO 3 -N/L in 2018, whereas the outlet nitrate concentrations typically ranged from 0.3 to 5.2 mg NO 3 -N/L in 2018. Nitrate tile-drainage effluent concentrations in 2019 were marginal, given soybeans obtain nitrogen from biological nitrogen fixa- tion. Nutrient uptake by corn reduced the soil nitrate leaching pool and created nitrogen-bearing biomass, features important for formulating best manage- ment practices. How to cite this paper: Aide, M., Braden, I., Mauk, D., McAlister, R. W., McVay, B., Murray, S., Siemers, S., Svenson, S., & Weathers, J. (2020). Tile-Drain and Deni- trification Bioreactor Water Chemistry for a Soybean (Glycine max (L.) Merr.)-Corn (Zea mays L.) Rotation in East-Central Missouri (USA). Journal of Geoscience and Environment Protection, 8, 143-154. https://doi.org/10.4236/gep.2020.84010 Received: January 31, 2020 Accepted: April 23, 2020 Published: April 26, 2020 Copyright © 2020 by author(s) and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access DOI: 10.4236/gep.2020.84010 Apr. 26, 2020 143 Journal of Geoscience and Environment Protection