Strategies to reduce CH4 and N20 emissions whilst maintaining crop yield in rice-wheat system under climate change using SPACSYS model

Context: Climate change is projected to threaten food security and stimulate greenhouse gas emissions. Hence, adaptation measures without sacrificing food production are required.
Objective: To assess possible consequences of rice system under climate change and to propose possible practices for mitigation.
Methods: The SPACSYS was tested using datasets from long-term experiment (since 1991) assessing the impact of different fertilisation on crop production, crop nitrogen (N) content, soil organic carbon (SOC) storage, methane (CH4) and nitrous oxide (N2O) emissions in a Cambisol under rice–wheat system. The validated SPACSYS was then used to investigate the possible mitigation strategies from 2024 to 2100 under climate change scenarios (SSP1–2.6 and SSP5–8.5) and the baseline scenario and management scenarios, i.e., (i) reduced N application rate by 20 % (RNA), (ii) the introduction of mid-season drainage (MSD) and (iii) integrated management (IM).
Results and conclusions: Results showed that SPACSYS performed effectively in simulating yield and N content in grain and straw, SOC storage and CH4 and N2O emissions, with R2 ranging from 0.21 to 0.67, modelling efficiency from 0.12 to 0.63 and index of agreement > 0.59. Scenarios analysis elucidated that RNA would not decrease grain yields for either rice or wheat under the two climate change scenarios. Compared to the baseline scenario, low level of climate change scenario considering the CO2 fertilisation effects (SSP1–2.6_CO2) may benefit wheat yield (28 %) and had no effects on rice yield. In contrast, under the SSP5–8.5 scenario, whether CO2 fertilisation effects are considered or not, both rice and wheat yield could face great loss (i.e., 11.8–29.9 % for rice, 8.3–19.4 % for wheat). The winter wheat would not be suitable for planting in the distant future (2070–2100) due to the incomplete vernalisation caused by warming. The switching from winter wheat to spring wheat from 2070 onward could avoid the yield loss by 8.3–19.4 %. Climate change could decrease SOC sequestration rate. Under the SSP1–2.6 and SSP5–8.5 scenarios, IM could reduce CH4 emissions by 55 % and 57 % and N2O emissions by 23 %, as such reducing the net global warming potential by 59 % compared to no adaptation. Our simulations suggest that under climate change, crop switching in rice–wheat system combining integrated mitigation practices is possible to mitigate global warming and maintain crop production.
Significance: Our results underscore the significance of integrated adaptation of agricultural systems to climate change.