Abstract:
Combination of global circulation models (GCMs), local-scale climate variability and crop simulation models were used to
investigate rain-fed sorghum yield response under current and future climate in central Tanzania. Decision Support System for
Agrotechnology Transfer (DSSAT) v.4.5 and Agricultural Production Systems Simulator (APSIM) v 7.4 were calibrated and evaluated
to simulate sorghum (Sorghum Bicolor L. Moench) var. Tegemeo in 2050s compared to baseline. Simulated median yields from both
crop models for the baseline (1980-2010) agree with the trend of yield over the years realistically. The models predicted yields of
sorghum in the range from 818 to 930 kg ha-1 which are close to the current national average of 1000 kg ha-1. Simulations by both
models using downscaled weather data from two GCMs (CCSM4 and CSIRO-MK3) under the Fifth Coupled Model Intercomparison
Project (CMIP5) and Representative Concentration Pathway (RCP 4.5) by mid-century show a general increase in median sorghum
yields. Median sorghum yields will increase by 1.1% - 7.0% under CCSM4 and by 4.0% - 12.5% under CSIRO-MK3. Simulations
for both current and future periods were run based on the present technology, current varieties and current agronomy packages. This
examination of impacts of climate change revealed that increase in sorghum yield will occur despite further projected declines or
increase in rainfall and rise in temperature. Modifying management practices through adjustment of sowing dates and the choice of
cultivars between improved and local are seemingly feasible options under future climate scenarios depending on the GCM and the
direction of the management practice. Our simulation results show that current improved sorghum cultivars would be resilient to
projected changes in climate by 2050s, hence bolstering the evidence of heat and drought tolerance in sorghum crop, thus justifying
its precedence as an adaptation crop under climate change. We conclude that despite the uncertainty in projected climate scenarios,
crop simulation models are useful tools for assessing possible impacts of climate change and management practices on sorghum.
