Strategies to reduce CH4 and N2O emissions whilst maintaining crop yield in rice–wheat system under climate change using SPACSYS model

Abstract

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–wheat system under climate change and to propose possible practices for mitigation.

METHODS

The Soil-Plant-Atmosphere Continuum SYStem (SPACSYS) model was tested using datasets from long-term experiment (1991–2019) assessing the impact of different fertilisation on crop production, crop nitrogen (N) content, soil organic carbon (SOC) stock, 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 mitigation management scenarios, i.e., (i) reduced N application rate by 20 % (RNA), (ii) the introduction of mid-season drainage (MSD) and (iii) integrated management combining RNA with MSD (IM).

RESULTS AND CONCLUSIONS

Results showed that SPACSYS performed effectively in simulating yield and N content in grain and straw, SOC stock and CH₄ and N₂O emissions. 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 future climate change scenarios, IM could significantly decrease CH₄ emissions by 56 % and N₂O emissions by 24 %, as such reducing the net global warming potential by 69 % 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.