Dissecting the contribution of weather and management on water table dynamics under present and future climate scenarios in the US Corn Belt

Abstract

In rainfed crop production regions such as the US Corn belt, the existence of a shallow water table increases crop productivity, decreases inter-annual grain yield variability, and impacts environmental N losses. Understanding how climate and management scenarios influence water table depth is key to designing sustainable and profitable cropping systems. A concurrent cropping systems-level examination of how weather variability, climate change, and agronomic management affect water table dynamics is missing. To fill this knowledge gap, we developed a systems evaluation using APSIM framework with the objectives to (1) quantify how weather and agronomic management (subsurface drainage, tillage, crop sequences) affect the water table depth and its seasonal variability under present and future (2020 to 2080) climate scenarios and (2) develop functional relationships between water table depth and productivity and sustainability indicators to increase our knowledge base. We considered four US Corn Belt environments with various water table depth conditions. Results indicated that the water table depth was mostly dictated by weather conditions, with management to alter water table depth by up to 31% under present climate conditions and up to 6% under future climate projections. The overall ranking of management practices in terms of influence on water table depth was subsurface tile drainage > tillage > crop sequence. The water tables will become slightly deeper in the future, with an overall downward trend of 0.18 cm year−1 (2020–2080), mostly driven by increased temperature and therefore evapotranspiration. For every degree increase in temperature, the water table depth deepened by about 8 cm. Water table depth affected crop yields, rooting depths, N2O emissions, and runoff in different ways revealing important tradeoffs between productivity and sustainability metrics. Our study provides new insights into an important water source for crop production, which can inform decision-making and climate change adaptation strategies.