dc.description.abstract |
Maize is the second most important cereal crop in eastern Ethiopia. However, climate change
and variability is affecting its productivity in the region. Thus, studies that included survey,
climate data analysis, and field experiment were therefore conducted with five objectives: 1) to
assess smallholder maize farmers’ perception of climate change, their current adaptation
options, and factors affecting their use of adaptation options in eastern Ethiopia; 2)to analyze
past and projected trends of rainfall and temperature parameters in Eastern and Western
Hararghe Zones, Ethiopia; 3) to calibrate and evaluate CERES-Maize model for the study
environment; 4) to assess the projected impact of climate change on maize productivity, and 5)
to evaluate the selected adaptation strategies to minimize the impact of climate change. In the
first chapter, data were collected from 364 household heads in three districts and six kebeles
based on maize production potential to assess the perception and response of maize farmers to
climate change. The multinomial logit model was used to evaluate determinants of climate
change perception and adaptation. The results of the study showed that smallholder maize
farmers perceived an increase in temperature (78%) and a reduction in rainfall (83%) amount.
Farmers also perceived climate variability in terms of erratic rainfall, late-onset and early
cessation were consistent with observed historical climate data analysis. Adaptation strategies
that the farmers apply to counteract the negative impact of climate change were found to be
influenced by socioeconomic and institutional factors. In the second chapter, a climate analysis
was made using data from five stations selected from East and West Hararghe Zones, based on a
relatively long period of past data records. Projected changes in rainfall and temperature under
the future climate periods (2030s and 2050s) under (Representative Concentration Pathways)
RCP4.5 and RCP8.5 from 17 CMIP5 (Coupled Model Inter-comparison Project Phase Five)
GCMs (Global Circulation Models) were also analyzed. The result of the study revealed that for
the past three decades rainfall showed variability. Maximum and minimum temperature showed
an increasing trend with significant Belg season minimum temperature across the study districts.
The ensemble model projection of rainfall and temperature in 2030s (2021–2050) and 2050s
(2041–2070) under RCP4.5 and RCP8.5 indicated a significant change in the parameters
compared to the baseline period (1988–2017). The mean annual minimum temperatures are
projected to increase by up to 2.92 °C in 2030, and 4.15 °C in 2050 while the mean maximum
temperature is expected to increase by 1.14 °C in 2030, and 1.87 °C in 2050. Annual rainfall
amount is also projected to increase by up to 29% in 2030, and 32% in 2050 under both RCP. In
the third chapter, a field experiment was conducted in 2019 and 2020 main crop growing
seasons using four maize cultivars at Haramaya, eastern Ethiopia to calibrate and evaluate the
CERES-maize model. In both experiments, treatments were arranged in a randomized complete
block design (RCBD) and replicated three times per treatment. Growth, development, and yield
data were collected for model calibration and evaluation. The result indicated that the CERES maize model well simulated the growth, development and yield of maize cultivars with observed
and simulated values in good agreement indicating that the model can be used to simulate maize
response to environmental factors in the study area. Hence, it can be used further for assessing
the impact and adaptation strategies under the conditions of Haramaya, eastern Ethiopia’s
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ecological conditions. In the fourth chapter, an impact analysis study was performed using
2030s and 2050s projected climate data under RCP4.5 and 8.5 with and without CO2
fertilization.The result of the study indicated that the projected changes in temperature and
rainfall by 2030s and 2050s without CO2 fertilization are expected to reduce the grain yields of
the maize cultivars by up to 12.3%, and 9.2%, respectively across GCMs under both RCP.
However, increased CO2 concentration across the studied cultivars and climate models
predicted an increase in grain yield by up to 1% in 2030s and 2% in 2050s compared to
simulated yield without CO2 fertilization under both RCP. In the fifth chapter, potential
adaptation practices (five planting dates, four nitrogen fertilizer rates, and two maize maturing
groups) were evaluated. According to the predicted result, the interaction effect of cultivars,
planting dates and nitrogen fertilizer rates significantly (p < 0.01) influenced maize grain yield
in the baseline climate. Planting late maturing (BH661) in the early 01 and mid (31 May) with
an application of 130.5 kg N ha–1
gave a higher yield than the rest of the treatments under the
baseline climate. In 2030s and 2050s under RCP4.5 and 8.5 the interaction effect of cultivars,
planting dates, and nitrogen fertilizer rates is predicted not to significantly influence maize grain
yield. However, in 2030s the interaction effect of cultivar and planting date, cultivar and
nitrogen fertilizer rate, and nitrogen fertilizer rates and planting date is projected to significantly
(p < 0.01) influence maize grain yield under RCP4.5 and 8.5. The results of the study indicated
that planting a late-maturing cultivar (BH661) on the 15th of May with an application of 130.5
kg N ha–1
predicted a higher yield than the rest of the treatments studied. In 2050s the
interaction effect of cultivar and nitrogen fertilizer rate under both RCP as well as nitrogen
fertilizer rates and planting dates under RCP8.5 significantly (p < 0.01) influence maize grain
yield. Planting late maturing (Raare-1) cultivar with 87 kg ha–1 nitrogen fertilizer application
under RCP4.5 and late maturing (BH661) cultivar with 130.5 kg ha–1 nitrogen fertilizer
application under RCP8.5 is predicted to give higher maize grain yield. The study, in general,
indicated an increase in temperature and variability of rainfall under the future climate affect
the productivity of maize in Eastern Ethiopia. Using late-maturing maize cultivars by optimizing
planting dates and fertilizer applications showed promise to offset the impact of climate change
on maize productivity in Eastern Ethiopia and similar environments. |
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