Unraveling the impacts of tile drainage on hydrology, biogeochemistry, and crop productivity in the U.S. Midwest: A Pathway to Climate Resilience
Tile drainage is an essential agricultural management practice to guarantee timely agricultural practice and secure crop productivity via removing excessive water in the U.S. Midwest. Previous studies have shown that tile drainage significantly changes hydrological and biogeochemical cycles by lowering the water table and reducing the residence time of soil water. However, these impacts of tile drainage still have large uncertainties, and how tile drainage further impacts crop growth through hydrological and biogeochemical paths remains poorly understood. Moreover, climate change is projected to bring wetter springs and drier summers to the U.S. Midwest region, raising concerns about crop resilience. We hypothesized that tile drainage would be a valuable adaptive approach to enhance crop resilience to climate change. In this study, we used an advanced process-based agroecosystem model, ecosys, to quantify the impacts of tile drainage on hydrological and biogeochemical cycles and crop growth at corn-soybean rotation fields in the U.S. Midwest. Tiles are represented as a water sink connected to the atmosphere, characterized by tile depth and tile spacing. Water flow from saturated soil layers to tiles is governed by the lateral hydraulic gradient defined by the water table depth in the field, tile depth, and tile density. Model results show that tile drainage decreases soil water content, and increases subsurface discharge. Consequently, this increased subsurface flow also elevated inorganic nitrogen leaching while simultaneously enhancing soil oxygen concentration. The presence of an aerobic condition due to tile drainage alleviated plant oxygen stress during wet springs, thereby promoting plant root growth. The development of stronger roots, in turn, mitigated water stress during dry summers, leading to an overall increase in crop yield. This study provides a comprehensive assessment of the function of tile drainage to hydrology, biogeochemical, and crop productivity, revealing the potential of tile drainage in bolstering crop resilience to climate change.