Simulating synergistic effects of climate change and conservation practices on greenhouse gas emissions and crop growth in long-term maize cropping systems

Understanding the impacts of future climate change and long-term agronomic practices on environmental quality and agricultural productivity is critical to the development of sustainable agronomic management approaches. Given these requirements, the present study's objective was to evaluate the potential impacts of climate change and long-term conservation practices on greenhouse gas (GHG) emissions and crop growth. To project potential future (2065-2084) climatic conditions for a field under a long-term maize cropping system situated in Nebraska (USA), 12 different combinations of regional climate models x global climate models (RCMs-GCMs) were generated under representative concentration pathway 8.5 (RCP8.5) and a heightened atmospheric carbon dioxide concentration ([CO2]atm = 714.1 ppm). Then, employing a well-calibrated instance of the Root Zone Water Quality Model (RZWQM2), the effects of four long-term conservation practices were simulated under the 12 RCMs-GCMs. Compared to other climatic factors (e.g., shortwave radiation, wind run, and relative humidity), temperature, precipitation, and [CO2]atm played more important roles for future carbon dioxide (CO2) and nitrous oxide (N2O) emissions, global warming potential (GWP), soil organic carbon (SOC), crop yield, and total crop biomass. The sum of their relative contributions to GHG emissions and crop growth exceeded 83.9 % across all treatments. Under future climatic conditions, CO2 and N2O emissions increased significantly - 19.4 % +/- 5.8 % and 26.6 % +/- 8.9 %, respectively - compared to those under historical baseline conditions. Likewise, the GWP increased by 19.8 +/- 5.8 %. Although rising [CO2]atm afforded limited benefits in terms of crop photosynthesis rates, rising future temperatures shortened crop growth cycles, resulting in a net decrease of 9.1 % +/- 1.9 % in maize yield and 4.2 % +/- 1.6 % in total biomass. SOC saw a net increase of 4.8 % +/- 0.4 % under the future (vs. baseline) climate. Compared to residue removal with no-till treatment, annual CO2 and N2O emissions in the long-term maize cropping system were predicted to increase by 26.8 % and 27.9 % between 2065 and 2084 under residue retention with tillage treatment, respectively. Whereas crop yield and biomass were not significantly affected by residue or tillage management practices. The simulation method provided valuable evidence for management decisions to assess the synergistic effects of climate change and long-term agronomic practices on the environment and agricultural productivity. Further investigation is needed on the effects of other climate RCPs and agronomic management for sustainable agricultural production.