Proceedings of the 2023 Mississippi Water Resources Conference

Year: 2023 Authors: Taylor J., Moore M., Hoeksema J., Locke M.

Important wetland properties associated with retention of excess nutrients and sediments in agricultural watersheds, as well as provision of critical food and habitat resources for migratory shorebirds, may be stimulated through novel implementation of existing wildlife BMPs in Lower Mississippi River Basin (LMRB) agroecosystems. We evaluated how novel timing (fall) of the implementation of NRCS EQIP 644 influenced nutrient runoff and denitrification in three inundated corn fields over a 3-month period. We observed significant positive N2-N flux rates (8 mg m2 h-1) soon after inundation that were sustained throughout the inundation period and culminated in an estimated 33-45 kg ha-1 of excess N removed by denitrification. We observed significant reductions in mean storm event loads for suspended sediments, NO3-N and PO4-P. We also observed significant reductions in TP loads, but NH4-N and TKN loads were not significantly affected by flooding. Flooded fields supported rapid colonization and maintenance of benthic macroinvertebrate densities (peak = ~5000 indv. m2) dominated by Chironomidae. Flooded fields provided critical habitat and food resources for migratory shorebirds with a minimum of 2100 individuals representing six shore bird species observed over four surveys during the fall migration period. Fields implementing shallow water habitat management in the fall had slight increases in soybean yields the following growing season. Our results suggest that novel timing of EQIP 644 provides temporary wetland structure and function that may support water quality improvements and provide critical shorebird habitat, without impacting yields within LMRB agroecosystems.