Assessment of climate change impact on rice yield and water footprint of large-scale and individual farming in Thailand.

Large-scale farming (participation in large-scale agricultural extension program) and individual farming (no participation) are two farming management practices of rice cultivation in Thailand, both of which cause significant water consumption and degradation and are vulnerable to climate change. However, given that climate change will influence both grain yield and water resource availability, it is not fully understood which type of farming management practice is more adaptive to climate change. This study aims to evaluate the adaptation capabilities of large-scale and individual farming by simulating rice yield changes under future climatic conditions and estimating the climate change impact on the water footprint (WF) of rice production. Rice management practices were obtained from large-scale and individual farming. Five General Circulation Models of RCP4.5 and RCP8.5 scenarios under four future time periods were used as future climate projections. Simulation results show a remarkable increase in rice yield of individual and large-scale farming under RCP4.5, ranging from 1.3 to 29.8% and 2.0 to 30.8%, respectively, whereas it fluctuates from 11.7 to -29.0% and 8.3 to -20.8% under RCP8.5 for individual and large-scale farming, respectively. The projected total WF of rice production under RCP4.5 will decline, ranging from -10.0 to -43.0% and -0.5 to -67.0% for individual and large-scale farming, respectively. Conversely, the RCP8.5 shows a fluctuation in projected total WF of -26.5 to 63.3% and -51.1 to 60.0% for individual and large-scale farming, respectively. The total WF, mainly grey WF, in large-scale farming is lower than in individual farming. The increase of rice yield under RCP4.5 is due to an increment of temperature and precipitation, resulting in a decrease of the total WF and vice versa for RCP8.5. The large-scale farms are highlighted as adopting appropriate management practices for rice production in which they can maintain rice yield and reduce grey WF.

Arunrat N ，Pumijumnong N ，Sereenonchai S ，Chareonwong U ，Wang C ... -  《-》

Evaluation of climate change impacts and adaptation strategies on rainfed rice production in Songkhram River Basin, Thailand.

This study investigates rice yield and evaluates potential adaptation measures on field management practices for rainfed rice production under climate change scenarios in the Songkhram River Basin, Thailand. The top-down and bottom-up approaches are combined to evaluate the future climate conditions in the Songkhram River Basin and identify adaptation strategies respectively. An ensemble of four Regional Climate Models (RCMs) bias-corrected using the Quantile Mapping technique was used to project the future climate under two climate change scenarios (RCP4.5 and RCP8.5). The DSSAT crop simulation model was used to simulate rice yield and evaluate the impacts of climate change on rice yield, as well as the feasibility of four adaptation options, which were solicited from four hundred farmers through questionnaire surveys in the basin. The strategies include (i) change in planting date, (ii) change in fertiliser application date, (iii) change in fertiliser application dose, and (iv) supplying irrigation water. Based on the model results, future maximum and minimum temperatures are expected to increase by 2.8 and 3.2 °C respectively under RCP8.5 scenario for 2080s. Although annual rainfall may be unchanged, rainfall patterns will shift earlier in future. Evaluation of adaptation strategies suggest that supplying irrigation water under RCP4.5 and RCP8.5 scenarios respectively are the best strategies to increase rice yield under climate change scenarios. Change in fertiliser application date and change in planting date can increase the future rice yield by 12 and 8%, respectively under RCP4.5 scenario for 2080s. Adjusting the fertiliser application dose may however reduce future rice yield. Although supplying irrigation water can aid the production of rainfed rice, other concerns such as the source of water are involved. The feasibility of adaptation actions would depend largely on available resources and mindset of farmers. Further work is warranted in exploring a combination of adaptation strategies and management plans to combat the adverse impacts of climate change.

Boonwichai S ，Shrestha S ，Babel MS ，Weesakul S ，Datta A ... -  《-》

Carbon footprint and predicting the impact of climate change on carbon sequestration ecosystem services of organic rice farming and conventional rice farming: A case study in Phichit province, Thailand.

Organic rice farming is a sustainable rice cultivation system that eliminates chemical inputs and has the potential to reduce environmental impacts. This study aims to: 1) evaluate and compare the carbon footprint intensity and the value of carbon sequestration ecosystem services (VCSES) between organic rice farming (OF) and conventional rice farming (CF) and 2) estimate the impact of climate change on soil organic carbon (SOC), rice yield, and VCSES of two farming types in Phichit province, Thailand. The results showed that the carbon footprint intensity in OF and CF were significantly different with -0.13 and 0.82 kg CO2eq kg-1 rice yield, respectively. The differences in SOC stocks (ΔSOCS) were more significant in OF with the increase of 1107.6 kg C ha-1 year-1 (4061.2 kg CO2eq ha-1 year-1), while the ΔSOCS value in CF was 625 kg C ha-1 year-1 (2291.7 kg CO2eq ha-1 year-1). The VCSES in OF (541,196 US$ ha-1 year-1) was nearly two times higher than in CF (305,388 US$ ha-1 year-1). Under future climate change, rice yields of both farming types are expected to increase under Representative Concentration Pathway (RCP) 2.6, RCP4.5, and RCP6.0, and it will decline under RCP8.5. The SOC and VCSES values are predicted to increase, except under RCP8.5. The dramatic declines can be found from the near future (2020-2039) to the very far future (2080-2099) period. Our finding indicates that even though climate change will have negative effects on SOC and VCSES, the OF will have less impact compared with CF.

Arunrat N ，Sereenonchai S ，Wang C 《-》

Assessment of climate change impact on the water footprint in rice production: Historical simulation and future projections at two representative rice cropping sites of China.

As one of the most important crops cultivated in China, rice contributes to approximately 28% of total yield. In despite of the substantial production, rice productivity is gravely affected by ongoing climate change and reduction of available water resources. Thus, assessing the responses of rice water consumption and productivity to more pronounced climate change is of great significance to water resources management in terms of relieving the resources shortage and meeting the food demand. In this study, the yield and water resources utilization during 1961-2010 in two typical rice plantation regions of China were evaluated using validated rice model ORYZA2000. Subsequently, their responses to future climate scenarios of 21 century were investigated through driving ORYZA2000 with downscaling climatic projections from GCMs under four RCPs emission scenarios. To quantify the water resources utilization in rice production from multiple perspectives, the water footprint (WF) and three water productivity indices (WPI, WPU and WPET) were integrated for assessing the regional agricultural water stress in this paper. The results revealed that the annual average linear inclining rates of WF in two stations (Kaifeng and Kunshan) were 3.86 m3/ t and 2.62 m3/ t, respectively. Moreover, compared with the green water footprint (WFg), the blue water footprint (WFb) is projected to significantly increase in future. The water productivity (WP) would decrease in two stations under four RCPs scenarios except that the WPu and WPET of Kunshan under RCP2.6 and RCP4.5 scenario in 2020s, 2050s and 2080s. Hence, this study provides insights into comprehensively understand the influences of climate change on food security and sheds lights on the regional strategy for future water resource management.

Zheng J ，Wang W ，Ding Y ，Liu G ，Xing W ，Cao X ，Chen D ... -  《-》

Climate change impact on major crop yield and water footprint under CMIP6 climate projections in repeated drought and flood areas in Thailand.

Understanding crop yield and water requirements in response to the future climate at the local scale is essential to develop more precise and appropriate adaptation strategies. From this perspective, repeated drought and flood events in the lower north of Thailand were investigated. The objectives of the study were to evaluate the impact of climate change on major crop yields and the water footprint (WF). Five global circulation model datasets from the sixth phase of the Coupled Model Intercomparison Project (CMIP6), known as Shared Socioeconomic Pathways (SSPs), were selected. Three future periods: near (2015-2039), mid (2040-2069), and far future (2070-2100) under SSP245 and SSP585 scenarios were used to predict the major crop yields and WF changes in the future. The precipitation and maximum and minimum temperatures were projected to increase in all periods under both scenarios. Rice yields in irrigated areas were predicted to rise gradually over the three projection periods under SSP245 but decline in mid and far-future periods under SSP585. There was a predicted reduction of first and second rice crop yields by -6.0% to -17.7% under SSP585. Fortunately, those rice yields were expected to increase in the near-future period under SSP245 by 3.0% to 4.3%. Growing maize, soybean, or mung bean instead of a second rice crop will have a less negative impact on future climate change. Changing from growing rice to be planting maize twice per year and growing cassava had increased favorability in rain-fed areas. The WF changes in the future were associated with future crop yield changes; therefore, the decrease in WFs was due to an increase in crop yield and vice-versa. The total WFs of maize, soybean, mung bean, and cassava production were roughly half that of rice production, indicating that these crops are suitable alternatives in the dry season.

Arunrat N ，Sereenonchai S ，Chaowiwat W ，Wang C ... -  《-》