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Assessment of the Effect of Climate Change on Boro Rice Production in Bangladesh Using Dssat Model

Jayanta Kumar Basak
Department of Civil Engineering Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh

M. Ashraf Ali
Department of Civil Engineering Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh

Md. Nazrul Islam
SAARC Meteorological Research Center, E-4/C Agargaon, Dhaka 1207, Bangladesh

Md. Abdur Rashid
Bangladesh Rice Research Institute, Gazipur-1701, Bangladesh

Abstract/ Executive Summary:

Effect of climate change on yield of two varieties of boro rice has been assessed using the DSSAT modeling system. The yield of BR3 and BR14 boro varieties for the years 2008, 2030, 2050 and 2070 have been simulated for 12 locations (districts) of Bangladesh. Available data on soil and hydrologic characteristics of these locations, and typical crop management practices for boro rice were used in the simulations. The weather data required for the model (daily maximum and minimum temperatures, daily solar radiation and daily precipitation) were generated for the selected years and for the selected locations using the regional climate model PRECIS. The model predicted significant reduction in yield of both varieties of boro rice due to climate change; average yield reductions of over 20% and 50% have been predicted for both rice varieties for the years 2050 and 2070, respectively. Increases in daily maximum and minimum temperatures have been found to be primarily responsible for reduction in yield. Increases in incoming solar radiation and atmospheric carbon-di-oxide concentration have been found to increase rice yield to some extent, but their effect is not significant compared to the negative effects of temperature. Variations in rainfall pattern over the growing period have also been found to affect rice yield and water requirement. Increasing temperatures and solar radiation have been found to reduce the duration of physiological maturity of the rice varieties. Model results also suggest that in addition to reducing yield, climate change may also make rice yield more vulnerable to transplanting date. DSSAT modeling system could be a useful tool for assessing possible impacts of climate change and management practices on different varieties rice and other crops.

Keywords: Bangladesh, Climate change, Boro rice, Rice yield, DSSAT model

Location: 12 districts of Bangladesh

Start Date: 00-00-2008

End Date:

Program Area: Socio-economic and Policy

Non-commodity: Modeling

Objectives:

The yield of two boro varieties (BR3 and BR14) have been simulated in the present study for the years 2008 (representing present time), 2030, 2050 and 2070, using the DSSAT modeling system. The future climate scenarios have been generated using the climate model named Providing Regional Climates for Impact Studies (PRECIS).

Methodology:

Selection of simulation locations The yield of two boro varieties BR3 and BR14 for the years 2008, 2030, 2050 and 2070 have been simulated for 12 districts of Bangladesh, which were selected from among the major rice growing areas in different regions of Bangladesh. Among them, Rajshahi, Bogra and Dinajpur were selected from northwestern region; Mymensingh and Tangail were selected from central region; Jessore and Satkhira from southwestern region; Barisal and Madaripur from southern region; Chandpur and Comilla from southeastern region; and Sylhet district from eastern region. In addition to simulating yield for the selected years under the simulated climatic scenarios and the selected crop management conditions (described later), potential yield (i.e., yield without any water and nitrogen stresses) and vulnerability of the rice varieties under varying transplanting date were also assessed. 2.2 Crop model The DSSAT modeling system is an advanced physiologically-based rice crop growth simulation model and has been widely applied to understanding the relationship between rice and its environment. The model estimates yield of irrigated and non-irrigated rice, determine duration of growth stages, dry matter production and partioning, root system dynamics, effect of soil water and soil nitrogen contents on photosynthesis, carbon balance and water balance. Ritchie et al. (1987) and Hoogenboom et al. (2003) have provided a detailed description of the model. In the present study, the Introductory Crop Simulation (ICSim) of DSSAT modeling system has been used for all simulations. 2.3 Selection of rice variety The DSSAT model is variety-specific (e.g., BR3 boro) and is able to predict rice yield and rice plant response to various environmental conditions. In predicting crop growth and yield, the model takes into effect of weather, crop management, genetics, and soil water, C and N. The model uses a detailed set of crop specific genetic coefficients, which allows the model to respond to diverse weather and management conditions. Therefore, in order to get reliable results from model simulations, it is necessary to have the appropriate genetic coefficients for the selected cultivars. The two boro rice varieties BR3 and BR14 have been selected in the present study because genetic coefficients for these varieties are available in the DSSAT modeling system. Although these varieties are not widely used at present time, the effects of climate change and variability on these varieties provide insights into possible impact of climate change on boro rice yield in the future. 2.4 Soil and crop management input The model requires a quite detailed set of input data on soil and hydrologic characteristics (i.e., pedological and hydrological data), and crop management. Input data related to soil characteristics include soil texture, number of layers in soil profile, soil layer depth, pH of soil for each depth, clay, silt and sand contents, organic matter, cation exchange capacity, etc. Required data on soil and hydrologic characteristics for the 12 selected locations (districts) were collected from Bangladesh Rice Research Institute (BRRI, Gazipur; BARC, 2005; Karim et al., 1998) and Soil Resources Development Institute (SRDI, Dhaka).

Source of Information: Journal of Civil Engineering (IEB), 38 (2) (2010) 95-108

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Although currently the BR3 and BR14 rice varieties are not widely used, the model simulations carried out in this study provide useful insight into the possible effects of climate change on boro rice yield. The growth and yield of crops are directly related to the rate of photosynthesis and phenology and their response to temperature, solar radiation and rainfall. Optimum temperatures for maximum photosynthesis range from 25 to 30 ºC for rice under the climatic conditions of Bangladesh. Increased temperatures during the growing season cause grain sterility. Very high temperatures, sometimes exceeding 35°C, have been predicted, especially for the years 2050 and 2070, due to climate change. Although there are significant uncertainties in the predicted climate parameters, the crop model simulation results suggest that if climate change causes significant increase in temperatures, this may in turn cause significant reduction in rice yield. Sensitivity analysis indicates that crop model is sensitive to CO₂ levels and solar radiation. Although higher CO₂ levels and solar radiation in the future would balance the detrimental effects of increased temperatures to some extent, these would not be able to offset the adverse effect of temperature. The model simulations also suggest that changes in rainfall patter may also adversely affect rice yield. Simulation results also suggest that planting dates could significantly affect rice yield, and this effect could become more pronounced in the future. In order to assess the effect of climate change on the rice varieties currently being grown in Bangladesh, it is necessary to determine their genetic coefficients through carefully controlled experiments. It is also necessary to develop high temperature-resistant rice varieties and modify management practices to offset the adverse effects of climate change. Modeling tools, such as the DSSAT modeling system, could be very useful in assessing possible impacts of climate change and management practices on rice yield. The predicted values of temperature and rainfall used in the present study are not calibrated on daily scale. Uncertainty in assessing possible impacts of climate change may also be reduced using high resolution climate model outputs with ensembles and calibrated outputs.

Knowledge Management: Journal