Author(s)

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.

Nitrogen transport from agriculture production fields raises the specter of environmental degradation of freshwater resources. Our objectives were to document 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 denitrification bioreactor is to create an environment for anoxic microbial populations to support denitrification. We monitored the tile-drainage effluent and denitrification bioreactor water chemistry under a corn-soybean rotation to estimate 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 NO₃^- -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 drainage 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 entering the denitrification bioreactor ranged from 0.4 to 103 mg NO₃^- -N/L in 2018, whereas the outlet nitrate concentrations typically ranged from 0.3 to 5.2 mg NO₃^- -N/L in 2018. Nitrate tile-drainage effluent concentrations in 2019 were marginal, given soybeans obtain nitrogen from biological nitrogen fixation. Nutrient uptake by corn reduced the soil nitrate leaching pool and created nitrogen-bearing biomass, features important for formulating best management practices.

Nitrogen, Edge of Field, Denitrification Bioreactor, Water Quality, Tile Drainage

Aide, M. , Braden, I. , Mauk, D. , McAlister, R. , McVay, B. , Murray, S. , Siemers, S. , Svenson, S. and Weathers, J. (2020) Tile-Drain and Denitrification 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. doi: 10.4236/gep.2020.84010.