RESUMEN
Future climate change-driven alterations in precipitation patterns, increases in temperature, and rises in atmospheric carbon dioxide concentration ([CO2]atm) are expected to alter agricultural productivity and environmental quality, while high latitude countries like Canada are likely to face more challenges from global climate change. However, potential climate change impact on GHG emissions from tile-drained fields is poorly documented. Accordingly, climate change impacts on GHG emissions, N losses to drainage and crop production in a subsurface-drained field in Southern Quebec, Canada were assessed using calibrated and validated RZWQM2 model. The RZWQM2 model was run for a historical period (1971-2000) and for a future period (2038 to 2070) using data generated from 11 different GCM-RCMs (global climate models coupled with regional climate models). Under the projected warmer and higher rainfall conditions mean drainage flow was predicted to increase by 17%, and the N losses through subsurface drains increase by 47%. Despite the negative effect of warming temperature on crop yield, soybean yield was predicted to increase by 31% due to increased photosynthesis rates and improved crop water use efficiency (WUE) under elevated [CO2]atm, while corn yield was reduced by 7% even with elevated [CO2]atm because of a shorter life cycle from seedling to maturity resulted from higher temperature. The N2O emissions would be enhanced by 21% due to greater denitrification and mineralization, while CO2 emissions would increase by 16% because of more crop biomass accumulation, higher crop residue decomposition, and greater soil microbial activities. Soil organic carbon storage was predicted to decrease 22% faster in the future, which would result in higher global warming potential in turn. This study demonstrates the potential of exacerbating GHG emissions and water quality problems and reduced corn yield under climate change impact in subsurface drained fields in southern Quebec.
RESUMEN
Greenhouse gas (GHG) emissions from agricultural soils are affected by various environmental factors and agronomic practices. The impact of inorganic nitrogen (N) fertilization rates and timing, and water table management practices on N2O and CO2 emissions were investigated to propose mitigation and adaptation efforts based on simulated results founded on field data. Drawing on 2012-2015 data measured on a subsurface-drained corn (Zea mays L.) field in Southern Quebec, the Root Zone Water Quality Model 2 (RZWQM2) was calibrated and validated for the estimation of N2O and CO2 emissions under free drainage (FD) and controlled drainage with sub-irrigation (CD-SI). Long term simulation from 1971 to 2000 suggested that the optimal N fertilization should be in the range of 125 to 175â¯kgâ¯Nâ¯ha-1 to obtain higher NUE (nitrogen use efficiency, 7-14%) and lower N2O emission (8-22%), compared to 200â¯kgâ¯Nâ¯ha-1 for corn-soybean rotation (CS). While remaining crop yields, splitting N application would potentially decrease total N2O emissions by 11.0%. Due to higher soil moisture and lower soil O2 under CD-SI, CO2 emissions declined by 6% while N2O emissions increased by 21% compared to FD. The CS system reduced CO2 and N2O emissions by 18.8% and 20.7%, respectively, when compared with continuous corn production. This study concludes that RZWQM2 model is capable of predicting GHG emissions, and GHG emissions from agriculture can be mitigated using agronomic management.