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Global food security faces increasing challenges from the changing climate. Changes of agricultural output from some of the most productive regions such as the US Corn Belt can largely affect the world's food market. Developing predictive understanding of the agricultural risk of climate change and potential mitigation strategies is critical for the global food security. The objective of this study is to assess the responses of maize and soybean yield to projected climate changes in the Corn Belt, identify the shifting environment stressors on crop yield, and tackle potential climate adaptation strategies. We drive a process-based model, the Decision Support System for Agrotechnology Transfer, with high-resolution statistically downscaled and bias-corrected historical and future climates from ten CMIP5 models in the MACA-2 database. The multi-model ensemble mean suggests a 12% decrease of maize yield by mid-century and 40% by late century, with a high degree of model consensus in the direction of changes; for individual models, the projected decrease of maize yield by late century ranges from <5% to over 80%, with the worst crop outcome corresponding to the most sensitive climate models. Soybean yield is projected to increase by midcentury with a high degree of model consensus, but such consensus is lost by late century as some projections shift to significant decreases. Crop yield in the Corn Belt is currently limited by water stress, but is projected to be increasingly limited by heat stress as well after the midcentury. The mounting heat stress will drive the most productive zone for maize to shift from central to northern part of the Corn Belt, but the projected increase in the northern states cannot fully compensate for the decrease in the south, causing the total production to decrease if agricultural practice stays the same. Earlier planting can alleviate only a small fraction of the heat-induced crop loss in a warmer climate. Climate change will (at least partially) offset the yield boost caused by agricultural technology and intensification. This study advances our predictive understanding of crop yield responses to climate change, and suggests that a multitude of strategies will be needed to address the climate change challenges for the U.S. agriculture. [Display omitted] • Yield decreases of 40% and 22% are projected for rain-fed maize and soybean respectively in the US Corn Belt by late century. • The primary limiting factor for the Corn Belt crop yield is projected to shift from water stress to heat stress after midcentury. • A northward shift or expansion of the most productive zone is projected. • The projected increase of yield and production in the northern states cannot fully compensate for the decrease in the south. • Earlier planting time can partially, but not completely, mitigate the heat-induced crop loss in the southern states. [ABSTRACT FROM AUTHOR]

We introduce a multistep modeling approach for studying optimal management of fertilizer inputs in a situation where soil nitrogen and carbon dynamics and water and atmosphere externalities are considered. The three steps in the modeling process are: (1) generation of the data sets with a detailed simulation model; (2) estimation of the system models from the data; (3) application of the obtained dynamic economic optimization model considering inorganic and organic fertilizer inputs. We demonstrate the approach with a case study: barley production in southern Finland on coarse and clay soils. Our results show that there is a synergy between climate change mitigation and water protection goals, and a trade-off between pollution mitigation and crop production goals. If a field is a significant source of greenhouse gas (GHG) emissions and an insignificant source of water pollution, atmospheric externalities dominate the water externalities, even for a relatively low social cost of carbon (SCC). If a field is a significant source of water pollution, the SCC would have to be very high before atmospheric externalities dominate water externalities. In addition, an integrated nutrient management system appears better than a system in which only inorganic or organic fertilizer is used, although manure is not a solution to agriculture's GHG emissions problem. Moreover, GHG emissions and nitrogen and carbon leaching mitigation efforts should first be targeted at coarse soils rather than clay soils, because the marginal abatement costs are considerably lower for coarse soils. • Economic study including N and C soil dynamics and water and climate externalities. • We constructed large systems of models from simulated data for economic optimization. • Water externalities must be considered in parallel to atmospheric externalities. • There is a synergy between climate change mitigation and water protection goals. • The marginal abatement costs are lower for coarse soils than for clay soils. [ABSTRACT FROM AUTHOR]