Optimizing rice management to reduce methane emissions and maintain yield with the CSM-CERES-rice model

Abstract

CONTEXT

Irrigated paddy fields are major contributors to methane (CH₄) emissions, significantly impacting global warming. Flood irrigation, the traditional method for rice cultivation, significantly increases water consumption and CH₄ emissions.

OBJECTIVE

The primary objective of this study was to quantify the benefits of deficit irrigation in reducing CH₄ emissions and maintaining yield compared to traditional flood irrigation using a systems analysis approach.

METHODS

The field study was conducted from May to August in both 2015 and 2016 at the Rice Research Institute in Amol, northern Iran. The site has a warm temperate climate, with the soil characterized as silty clay loam. The data collected during these two years were used for the calibration and evaluation of the CSM-CERES-Rice model. Calibration was performed using the data collected in 2016 while the model's performance was evaluated using data collected in 2015. Following model calibration and evaluation, a seasonal analysis was employed to assess alternative management practices for single growing seasons. This analysis feature of DSSAT allowed us to evaluate alternate management scenarios with the model using 35 years of long-term historical daily weather data from 1984 to 2018 obtained from a local weather station.

RESULTS AND CONCLUSIONS

The simulation revealed that early rice planting, in April or May, yielded the highest production and the lowest CH₄ emissions, when using the direct seeding method. This strategy resulted in a 15 % increase in yield, 13 % better irrigation efficiency, and a 9 % reduction in CH₄ emissions compared to transplanting. Among tillage systems, no-tillage further reduced CH₄ emissions by 29 % without compromising yield or irrigation efficiency. Although sowing depth did not significantly affect CH₄ emissions or yield, an optimal depth of 10–15 cm was identified. Additionally, maintaining a plant population of 10 transplants per hill exhibited the lowest CH₄ emissions compared to higher plant populations. Higher nitrogen fertilization rates increased both yield and CH₄ emissions. In conclusion, the best approach among different strategies was early cultivation for direct-seeded rice coupled with a nitrogen fertilizer rate of 250 kg ha⁻¹, resulting in both the highest yield and the lowest emissions simultaneously.

SIGNIFICANCE

The findings from this study offer a comprehensive exploration, identifying specific agronomic practices that optimize rice cultivation by enhancing yield, conserving water, and significantly reducing CH₄ emissions, thereby providing actionable insights for policymakers and farmers in fostering sustainable agriculture.