Validation of the DNDC-Rice model by using CH₄and N₂O flux data from rice cultivated in pots under alternate wetting and drying irrigation management

Abstract

The DNDC (DeNitrification-DeComposition)-Rice model, one of the most advanced process-based models for the estimation of greenhouse gas emissions from paddy fields, has been discussed mostly in terms of the reproducibility of observed methane (CH 4 ) emissions from Japanese rice paddies, but the model has not yet been validated for tropical rice paddies under alternate wetting and drying (AWD) irrigation management, a water-saving technique. We validated the model by using CH 4 and nitrous oxide (N 2 O) flux data from rice in pots cultivated under AWD irrigation management in a screen-house at the International Rice Research Institute (Los Bañ os, the Philippines). After minor modification and adjustment of the model to the experimental irrigation conditions, we calculated grain yield and straw production. The observed mean daily CH 4 fluxes from the continuous flooding (CF) and AWD pots were 4.49 and 1.22 kg C ha À1 day À1 , respectively, and the observed mean daily N 2 O fluxes from the pots were 0.105 and 34.1 g N ha À1 day À1, respectively. The root-mean-square errors, indicators of simulation error, of daily CH 4 fluxes from CF and AWD pots were calculated as 1.76 and 1.86 kg C ha À1 day À1, respectively, and those of daily N 2 O fluxes were 2.23 and 124 g N ha À1 day À1, respectively. The simulated gross CH 4 emissions for CF and AWD from the puddling stage (2 days before transplanting) to harvest (97 days after transplanting) were 417 and 126 kg C ha À1 , respectively; these values were 9.8% lower and 0.76% higher, respectively, than the observed values. The simulated gross N 2 O emissions during the same period were 0.0279 and 1.45 kg N ha À1 for CF and AWD, respectively; these values were respectively 87% and 29% lower than the observed values. The observed total global warming potential (GWP) of AWD resulting from the CH 4 and N 2 O emissions was approximately one-third of that in the CF treatment. The simulated GWPs of both CF and AWD were close to the observed values despite the discrepancy in N 2 O emissions, because N 2 O emissions contributed much less than CH 4 emissions to the total GWP. These results suggest that the DNDC-Rice model can be used to estimate CH 4 emission and total GWP from tropical paddy fields under both CF and AWD conditions.

Greenhouse gas emission from direct seeded paddy fields under different soil water potentials in Eastern India

“…This may be due to prolonged dry spell, which resulted in extremely aerobic soil condition with high Eh, which was difficult to revert to the anaerobic condition with low Eh, essential for CH 4 production after re-flooding during the rice growing season. Our results support an earlier finding by Katayanagi et al (2012), who reported a decrease in CH 4 emission (73%) using an alternate wet and dry irrigation strategy during rice cultivation. Our results suggest that scheduling irrigation at different SWPs in direct seeded rice reduces CH 4 flux and hence significantly decreases the seasonal cumulative CH 4 emission ( Fig.…”

Effects of water-saving irrigation practices and drought resistant rice variety on greenhouse gas emissions from a no-till paddy in the central lowlands of China

“…Compared with CF treatment, the averaged seasonal CH 4 fluxes for both rice varieties were significantly reduced (p b 0.01) by 59% in FWI plots and 83% in the FDI plots. Our results support an earlier study by Katayanagi et al (2012) who found a 73% mitigation of CH 4 emission using an AWD irrigation strategy during rice cultivation. Thus, decreasing soil water content through water management is thought to be the most promising option for methane mitigation (Yagi et al, 1996;Li et al, 2005;Minamikawa and Sakai, 2006;Tyagi et al, 2010).…”

Novel Technological and Management Options for Accelerating Transformational Changes in Rice and Livestock Systems

“…The percent reductions in CH 4 emissions were similar to those observed by Thawda et al [34] and Katayanagi et al [35], who also reported high CH 4 emission reductions with AWD (65 to 73%). Our results show that, compared to continuous flooding, water management strategies such as AWD have mitigation benefits under both El Niño and La Niña conditions.…”