Climate change impacts are visible in Bangladesh which requires adoption of judicious crop management practices for sustainable agriculture. Crop simulation models are effective in this regard and can be used for optimizing water and nitrogen inputs for maximization of wheat yields. Two field studies were conducted at Bangladesh Agricultural Research Institute (BARI) for evaluating the effect of increased temperature on wheat production under variable water and N rates, through the use of DSSAT v4.6 model. Thirty years historic weather data and BARI Gom-26 wheat-cultivar coefficients, as generated through use of GLUE of DSSAT model, were used for evaluating the impact of temperature rise with variable rates of irrigation water and nitrogen. The effects of four levels of nitrogen (0, 40, 80 and 120 kg ha - 1 ) and four irrigation levels [0 (no irrigation), 1, 2 and 3] on wheat yield were evaluated under 0°C, 1°C, 2°C and 3°C rise in temperature. Simulation results indicated that wheat yield increased with increase in nitrogen application rate, but decreased with the temperature rise. Crop growing duration was reduced by about five days for each degree rise in temperature, irrespective of levels of irrigation water and nitrogen-rates. In general, there was yield reduction of 8.13, 16.77 and 24.97 % with increased temperature of 1°C, 2°C and 3°C, respectively, when compared with no temperature rise treatment. For interaction of temperature rise-N dose, the magnitude of yield decline under temperature rise was higher with increased dose of N. Agronomic N use efficiency at different N rates and temperature rise level were calculated. N use efficiency decreases with the increase in temperature rise and the highest (29.95 kg grain kg - 1 N) was obtained from 40 kg N ha -1 treated plot with 0 °C temperature rise <i> i.e </i> . existing atmospheric temperature. Simulation results indicated increase in wheat yield with higher levels of irrigation water, and interaction of irrigation level with temperature rise was significant. I rrigation use efficiency decrease s with the increase in temperature rise. From the present study, it was seen that the interaction of temperature rise with varying levels of N and irrigation water was significant, and there is a need to design the appropriate inputs’ management, as the adaptation strategy, to sustain the wheat yield under climate change situation .
Crop growth models play important role in agricultural research, especially in the decision system of technology development, research management and policy options [
Wheat is the second most important cereal crop in Bangladesh and environment friendly in terms of irrigation water requirement, but sensitive to increased temperature. Nitrogen and irrigation water management not only help in achieving improved wheat yield, but it also mitigates greenhouse gas (GHG) emission from the crop fields. Though wheat is grown even under reduced irrigation conditions or residual soil moisture, climate change impacts may cause reduced water availability in future agriculture of Bangladesh and there is a need to identify the effect of soil moisture availability on growth and yield of wheat. Simulation study through crop modelling can predict crop performance against raising temperature scenarios of Bangladesh, by also integrating the interaction effect of other biotic and abiotic stresses.
Nitrogen is the key nutrient for wheat production. Crops grown in Bangladesh are more responsive to nitrogen than other nutrients. Similarly irrigation is an important input for crop production. Wheat grows in winter season of Bangladesh when no rainfall occurs and thereby less moisture prevail in the soil. So irrigation is essential for better wheat production. But both nitrogen and irrigation are expensive input for crop production. Field experiments for quantifying optimal crop N and irrigation water requirement are time-consuming, require many years of trials at multiple locations [
Decision Support System for Agrotechnology Transfer (DSSAT v4.6) is a popular modelling system [
The simulation study was conducted at Bangladesh Agricultural Research Institute (BARI) by using DSSAT v.4.6 model during growing season of 2016-2017 at Dinajpur (25.63˚N and 88.63˚E and 39 m above mean sea level), which is the major wheat growing region of Bangladesh. Soil properties of the test site are given in
DSSAT is a comprehensive crop growth model which includes more than 40 crops. The Crop Estimation Resource and Environment Synthesis (CERES)- Wheat model was one of the models developed through the International Benchmark Sites Network for Agrotechnology Transfer (IBSNAT) project which can simulate growth and yield of wheat varieties under all agro-climatic conditions [
Soil layer (cm) | Sand (%) | Silt (%) | Clay (%) | Bulk density (g∙cm−3) |
---|---|---|---|---|
0 - 15 | 61.0 | 22.7 | 16.3 | 1.49 |
15 - 30 | 66.3 | 11.7 | 27.3 | 1.57 |
30 - 60 | 58.3 | 11.0 | 30.7 | 1.59 |
60 - 90 | 55.9 | 9.4 | 34.7 | 1.61 |
90 - 120 | 67.3 | 14.4 | 18.3 | 1.62 |
120 - 150 | 74.3 | 6.4 | 19.3 | 1.67 |
150 - 180 | 74.3 | 6.3 | 19.4 | 1.69 |
Soil layer (cm) | pH | Organic carbon (%) | Total N (%) | Available phosphorous (mg∙kg−1) | Available potassium (mg∙kg−1) | ||
---|---|---|---|---|---|---|---|
0 - 15 | 6.1 | 0.49 | 0.05 | 9.8 | 2.0 | 6.27 | 0.26 |
15 - 30 | 6.2 | 0.28 | 0.03 | 7.3 | 2.1 | 6.03 | 0.24 |
30 - 60 | 6.2 | 0.19 | 0.02 | 5.1 | 2.2 | 5.18 | 0.22 |
60 - 90 | 6.3 | 0.14 | 0.01 | 4.7 | 2.5 | 4.83 | 0.19 |
90 - 120 | 6.4 | 0.13 | 0.01 | 4.3 | 2.7 | 3.98 | 0.16 |
120 - 150 | 6.5 | 0.12 | 0.01 | 3.5 | 3.2 | 3.19 | 0.15 |
150 - 180 | 6.7 | 0.10 | 0.01 | 3.0 | 3.4 | 2.88 | 0.13 |
Month | Average temperature (˚C) | Total rainfall (mm) | Sunshine hour | |
---|---|---|---|---|
Maximum | Minimum | |||
November | 29.0 | 16.6 | 15.2 | 7.82 |
December | 25.1 | 12.2 | 6.9 | 6.49 |
January | 22.9 | 10.4 | 8.8 | 5.94 |
February | 26.5 | 13.0 | 12.7 | 7.51 |
March | 30.9 | 17.4 | 11.4 | 8.09 |
April | 32.9 | 21.1 | 65.7 | 7.41 |
includes various tools like XBuild to create and modify experiment files, GBuild for graphing of outputs, SBuild for soil database, Weatherman for weather data and GLUE for genetic coefficient. Data on weather, soil and crop characteristics and various crop management options were used as input data. Solar radiation, air temperature (maximum and minimum in ˚C) and precipitation (mm) were used as weather data while soil physical properties like texture, structure, bulk density, water holding capacity and chemical properties like pH, N, P, K content were used as soil data. Experimental data on time series biomass and leaf area index were used as crop data.
In order to simulate yields under changing temperature scenarios, the CERES- Wheat model in DSSAT was calibrated and validated. Climatic data were collected from the weather station of Dinajpur, which operates under the Department of Metrology, Government of Bangladesh. The input files, such as weather file, soil file, X file (experimental file), A file (average measured data file) and T file (seasonal file) were prepared for using CERES-Wheat model to predict wheat yield under temperature rise and variable water and nitrogen inputs.
Two separate simulated studies were carried out to predict rise in temperature impact on wheat yield. In first study, the effects of rising temperature (0˚C, 1˚C, 2˚C and 3˚C) on wheat yield under variable nitrogen inputs viz. 0, 40, 80 and 120 kg N ha−1 were investigated. In second study, variable irrigation levels viz. 0, 1, 2 and 3 to create differential soil water regimes, in combination with temperature rise scenarios of 0˚C, 1˚C, 2˚C and 3˚C, were used to simulate the effect on growth and yield of wheat crop.
The simulation runs were made with wheat variety, BARI Gom-26, through conducted field trials, and crop coefficients were generated through run of tool GLUE of DSSAT. Genetic coefficients were computed, and performance evaluation was done through comparison of observed and simulated values for various field experiments compiled from BARI sub-stations in various production environments of Bangladesh.
Predicted wheat yield was generated using seasonal run from 1980 to 2010. The scenarios were developed to assess the sensitivity of the crop to rising temperature with varying level of N and irrigation number. Calibrated DSSAT model for wheat grown in Bangladesh environment was used to evaluate the impact of these scenarios of interaction of temperature with varying irrigation water and nitrogen inputs, and the outputs were analyzed using graphical techniques to compare climate change effect on growth and yield of wheat.
Agronomic N use efficiency at different N rate and temperature rise level was calculated with the following equation [
where GYF = Grain yield (kg ha−1) in N-fertilized plot, GY0 = Grain yield (kg ha−1) in zero N-fertilized plot and FN was total fertilizer N applied (kg ha−1).
Irrigation use efficiency at different irrigation and temperature rise level was calculated with the following equation:
where GYI = Grain yield (kg ha−1) in irrigated plot, GI0 = Grain yield (kg ha−1) in unirrigated plot and IN was total number of irrigation.
With the help of several wheat trials (with dates of sowing, irrigation and nitrogen rates), the genetic coefficients were computed by use of tool GLUE of DSSAT (
The P1V is optimum vernalizing temperature, required for vernalization expressed in days, PID indicates photoperiod response (% reduction in rate/10 h drop in pp), P5 is grain filling (excluding lag) phase duration (˚C-d). G1, G2 and G3 means kernel number per unit canopy weight at anthesis (#/g), standard kernel size for wheat grown under optimum conditions (mg) and standard, non- stressed mature tiller weight (including grain) (g dwt); respectively. PHINT indicates interval between successive leaf tip appearances expressed in ˚C-d.
Variety | P1V | P1D | P5 | G1 | G2 | G3 | PHINT |
---|---|---|---|---|---|---|---|
BARI Gom-26 | 0 | 92 | 730 | 23 | 46 | 3.8 | 70 |
Simulation results, with long term historic weather, indicated that maximum leaf area index (LAImax) increased with the increase in N rate and decrease with temperature rise (
The highest values of days to maturity (i.e. 114 d) was obtained under no temperature rise and the lowest value of 100d was obtained under 3˚C rise in temperature treatment, with corresponding values of 110d and 105d under 1˚C and 2˚C temperature, respectively (
Effect of rise in temperature and nitrogen-N application on grain yield of wheat is shown in
interaction of temperature rise-N dose, the magnitude of yield decline under temperature rise was higher with increased dose of N.
Agronomic N use efficiency at different N rates and temperature rise level (compare with 0 kg N ha−1) were calculated and presented in
Effect of rise in temperature and variable irrigation levels on maximum leaf area index at anthesis (LAI) of wheat is shown in
N rate (kg ha−1) | Temperature rise level | |||
---|---|---|---|---|
0˚C | 1˚C | 2˚C | 3˚C | |
40 | 29.95 | 25.08 | 19.58 | 13.73 |
80 | 22.64 | 16.89 | 12.48 | 8.70 |
120 | 17.20 | 12.80 | 9.68 | 7.22 |
Simulation results indicated that grain yield of wheat increased with the increase of irrigation level, but decreased with rise in temperature (
Irrigation use efficiency at different irrigations and temperature rise level (compare with 0 irrigation i.e. un-irrigated plot) were calculated and presented in
Irrigation level | Temperature rise level | |||
---|---|---|---|---|
0˚C | 1˚C | 2˚C | 3˚C | |
1 | 750 | 737 | 714 | 695 |
2 | 1223 | 1155 | 1080 | 974 |
3 | 1061 | 902 | 772 | 709 |
efficiency was lowest in 3˚C temperature rise followed by 2˚C and 1˚C temperature rise. Highest irrigation use efficiency was obtained from 0˚C temperature rise i.e. existing atmospheric temperature. Irrigation use efficiency increase with the increase in irrigation level upto two irrigation and decreased thereafter. Because between 1 to 2 irrigation, wheat yield increased highly (
Climate change and its variability are major concerns in Bangladesh. Rising temperature is the main phenomena in climate change. Wheat is an important crop of the country, and there is a need to evaluate the impact of temperature rise on growth and yield under variable rates of irrigation water and nitrogen. DSSAT version 4.6 was calibrated for important wheat cultivar and subsequently taken to simulate the effect of temperature rise with irrigation water and nitrogen interaction at Dinajpur. Historic weather dataset, soil parameters were used. Wheat yield decreased with increase in temperature, due to reduced duration of the crop and considerable reduction in the maximum leaf area index at flowering. Simulated yield of wheat increased with increased levels of irrigation water and nitrogen. The interaction of rise in temperature with the irrigation water and nitrogen inputs was significant, and the crop simulation tools could successfully guide in optimizing these major inputs with regard to temperature rise scenarios. Simulation of nitrogen-N and irrigation water management strategies using DSSAT models can, therefore, lead to better irrigation water and nitrogenous fertilizer decision-making.
The authors gratefully acknowledge the financial support provided by Bangladesh Krshi Gobeshona Foundation (KGF) under the project entitled “Modelling Climate Change Impact on Agriculture and Developing Mitigation and Adaptation Strategies for Sustaining Agricultural Production in Bangladesh” executed by BARI, BRRI and BSMARU.
The authors declare no conflict of interest.
Sen, R., Choudhury, A.K., Akhter, S., Ishtiaque, S., Jahan, M.A.H.S., Ahmed, F., Biswas, J.C., Maniruzzaman, M., Miah, M.M.U., Rahman, M.M., Kalra, N., Aziz, M.A. and Khan, A.S.M.M.R. (2017) Simulating Nitrogen and Irrigation Effects on Wheat Production in Bangladesh under Changing Climate. American Journal of Plant Sciences, 8, 1593-1606. https://doi.org/10.4236/ajps.2017.87110