Abstract
Harmful algal blooms (HABs) are increasing in frequency and severity worldwide due to nonpoint source nutrient pollution, mainly a product of agricultural runoff. This issue is compounded by the steady, global loss of wetlands and their water quality services. Wetlaculture, an integrated system of wetlands and agriculture, has been proposed as a solution to HABs in which farmland located on former wetlands is flipped to serve as a nutrient-sequestering treatment wetland for a period of years, then flipped back to farmland which consumes the stored nutrients for crop production without the need for fertilizers. A wetlaculture mesocosm experiment was initiated at Buckeye Lake, Ohio in 2016, where all of the site's mesocosms had been functioning as treatment wetlands fed with water from an adjacent, nutrient-impaired stream prior to the 2020 season. This study serves as both a continuation of the treatment wetland experiment, and a first attempt at the cultivation of an agricultural crop in wetlaculture mesocosms. Eight of the twenty-eight mesocosms were drained and planted with corn (Zea mays), while the remaining twenty continued to function as treatment wetlands. Inflow and outflow concentrations of five nutrient species were monitored in the wetland mesocosms, while suitability for corn was evaluated via preplant soil tests and ultimate grain yield, which was compared to that of a nearby commercial farm. End-of-season soil analyses from both the corn and wetland mesocosms were taken to determine the impact of these disparate management regimes on total soil N, P, K, and C. Results indicate that the treatment wetlands continued to improve water quality and that the mesocosms planted with corn produced a grain crop without fertilization. Mesocosm yields (58 ± 9.5 bu./ac) fell significantly below those of the reference farm (160 ± 15.3 bu./ac)(p = 0.004). Some of that difference may be due to the frequent herbivory that occurred during this study, in addition to the limited soil volume in the 0.285 m3 mesocosm tubs versus the open agricultural field.
