Linking measurements and models to estimate landscape-scale impacts of agricultural management on soil carbon and groundwater use

Agricultural management changes can be small in scale or impact, but may have the potential to shift biogeochemical cycles at landscape and larger scales. Understanding which practices can address landscape scale challenges, such as climate change mitigation or groundwater conservation, requires scaling up estimates spatially and temporally. Two examples will be presented for the integration of measurements into models. The first will focus on the potential for crop rotation shifts at the landscape scale to mitigate or support adaptation to climate change. We used on-farm, long-term, and landscape scale datasets to estimate how crop rotations impact soil organic carbon (SOC) accumulation rates under current and future climate scenarios across the semi-arid Central Great Plains. Replacing traditional wheat-fallow rotations with more diverse, continuously cropped rotations increased SOC by 17% and 12% in 0-10 cm and 0-20 cm depths, respectively, and reduced herbicide use by 50%. Using USDA Cropland Data Layer, we estimated soil C accumulation and pesticide reduction potentials of shifting to more intensive rotations. We also used a 30-year cropping systems experiment to calibrate and validate the Daycent model to evaluate rotation intensity effects under future climate change scenarios. The model estimated greater SOC accumulation rates under continuously cropped rotations, but SOC stocks peaked and then declined for all cropping systems beyond 2050 under future climate scenarios. Perennial grasslands were the only system estimated to maintain SOC levels in the future. Our findings highlight the potential vulnerability of semi-arid regions to climate change, which will be compounded by declining groundwater levels along the western edge of the High Plains Aquifer that will increase reliance on dryland farming systems. The second example will present an example of the potential opportunities and challenges for integrated modeling approaches to evaluate crop and irrigation management practice impacts on crop productivity and groundwater demand across the High Plains aquifer region. Linking measurements with models provides opportunities to develop future transition and adaptation strategies in partnership with producers, policy makers, and rural communities.