Carbon sequestration and emissions mitigation in paddy fields based on the DNDC model: A review

Since each greenhouse gas (GHG) has its own radiative capacity, all three gasses (CO2, CH4 and N2O) must be accounted for by calculating the net global warming potential (GWP) in a crop production system. To compare the impact of GHG fluxes from the rice growing and the fallow season on the annual gas fluxes, and their contribution to the GWP and carbon sequestration (CS) were evaluated. From May to April in Bibai (43°18′ N, 141°44′ E), in central Hokkaido, Japan, three rice paddy fields under actual management conditions were investigated to determine CS and the contribution of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes to GWP. Methane and N2O fluxes were measured by placing the chamber over the rice plants covering four hills and CO2 fluxes from rice plants root free space in paddy fields were taken as an indicator of soil microbial respiration (Rm) using the closed chamber method. Soil CS was calculated as the difference between net primary production (NPP) and loss of carbon (C) through Rm, emission of CH4 and harvest of crop C. Annual cumulative Rm ranged from 422 to 519 g C m−2 yr−1; which accounted for 54.7 to 55.5% of the rice growing season in particular. Annual cumulative CH4 emissions ranged from 75.5 to 116 g C m−2 yr−1 and this contribution occurred entirely during the rice growing period. Total cumulative N2O emissions ranged from 0.091 to 0.154 g N m−2 yr−1 and from 73.5 to 81.3% of the total N2O emissions recorded during the winter-fallow season. The CS ranged from −305 to −365 g C m−2 yr−1, suggesting that C input by NPP may not be compensate for the loss of soil C. The loss of C in the winter-fallow season was much higher (62 to 66%) than in the growing season. The annual net GWP from the investigated paddy fields ranged from 3823 to 5016 g CO2 equivalent m−2 yr−1. Annual GWPCH4 accounted for 71.9 to 86.1% of the annual net GWP predominantly from the rice growing period. These results indicate that CH4 dominated the net GWP of the rice paddy.

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Modeling Climate Change Effects on Rice Yield and Soil Carbon Under Variable Water and Nutrient Management

Sustainability ◽

10.3390/su13020568 ◽

2021 ◽

Vol 13 (2) ◽

pp. 568

Author(s):

Zewei Jiang ◽

Shihong Yang ◽

Jie Ding ◽

Xiao Sun ◽

Xi Chen ◽

...

Keyword(s):

Climate Change ◽

Organic Carbon ◽

Bayesian Model Averaging ◽

Rice Yield ◽

Paddy Fields ◽

Dndc Model ◽

Carbon Management ◽

Rice Yields ◽

Rcp 8.5 ◽

The Impact

Soil organic carbon (SOC) conservation in agricultural soils is vital for sustainable agricultural production and climate change mitigation. To project changes of SOC and rice yield under different water and carbon management in future climates, based on a two-year (2015 and 2016) field test in Kunshan, China, the Denitrification Decomposition (DNDC) model was modified and validated and the soil moisture module of DNDC was improved to realize the simulation under conditions of water-saving irrigation. Four climate models under four representative concentration pathways (RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5), which were integrated from the fifth phase of the Coupled Model Intercomparison Project (CMIP5), were ensembled by the Bayesian Model Averaging (BMA) method. The results showed that the modified DNDC model can effectively simulate changes in SOC, dissolved organic carbon (DOC), and rice yield under different irrigation and fertilizer management systems. The normalized root mean squared errors of the SOC and DOC were 3.45–17.59% and 8.79–13.93%, respectively. The model efficiency coefficients of SOC and DOC were close to 1. The climate scenarios had a great impact on rice yield, whereas the impact on SOC was less than that of agricultural management measures on SOC. The average rice yields of all the RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5 scenarios in the 2090s decreased by 18.41%, 38.59%, 65.11%, and 65.62%, respectively, compared with those in the 2020s. The long-term effect of irrigation on the SOC content of paddy fields was minimal. The SOC of the paddy fields treated with conventional fertilizer decreased initially and then remained unchanged, while the other treatments increased obviously with time. The rice yields of all the treatments decreased with time. Compared with traditional management, controlled irrigation with straw returning clearly increased the SOC and rice yields of paddy fields. Thus, this water and carbon management system is recommended for paddy fields.

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