Abstract:
Potato is a very important food and cash crop especially in the high and mid altitude areas of
Ethiopia. However, its production and productivity are seriously affected by temperature and
rainfall variability. Hence, it is important to identify the degree of climate change in specific
locality either by determining the perceptions of farmers on the change or analyzing weather
variables obtained from meteorological station and projected values through Marksim Weather
generator obtained from different GCM models. Therefore, the current study was carried out
with specific objectives (i) to analyze past and future climate parameters in the major potato
growing areas of eastern Ethiopia; (ii) to calibrate and evaluate the potato crop model
(SUBSTOR-potato) for eastern Ethiopia; (iii) to understand and analyze farmers’ perception of
climate change and variability, and factors influencing their coping mechanisms and adaptation
measures; (iv) to estimate the impact of climate change on potato productivity under different
climate change scenarios; and (v) to identify and evaluate adaptation options for potato
production under future climate. For the analysis of annual and seasonal trends of rainfall and
temperature, onset and cessation dates of rainfall, length of growing period (LGP) and dry spell
length; long term data(1980-2017) were used from three meteorological stations in Eastern
Ethiopia (Haramaya, Chiro and Kombolcha). A total of 222 sample households were used from
four districts (Haramaya, Kombolcha, Kersa and Jarso) to understand farmers’ perception and
the data were analyzed using descriptive statistics and Multinomial Logit Model (MNL). For
climate impact assessment MarkSim weather generator was used to downscale future climate
data (2030s and 2050s) of three stations for two emission pathways (RCP4.5 and RCP8.5). The
Decision Support System for Agro-technology Transfer (DSSAT) model was used to assess the
impact of future climate on the yield of three potato varieties (Bubu, Zemen and Bate). The
model was also run to simulate the projected yield of the crop under different crop management
(adaptation) options of nitrogen fertilizer levels and planting dates. The Mann-Kendall test
revealed a non-significant decreasing trend of the annual rainfall at Haramaya, Chiro and
Kombolcha and significanly increasing trend of Kiremt rainfall at Haramaya. Both seasonal and
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annual maximum temperatures at Haramaya showed significantly increasing trend whiles
minimum temperature revealed a non-significant increase both for annual and Kiremt season.
On the other hand, the projection study indicated that the mean annual future maximum
temperature could rise by up to 1.4ºC and 0.35ºC for RCP4.5 in 2030s and 1.53 ºC and 0.5 ºC,
for RCP8.5 in 2030s at Haramaya and Chiro, respectively. Both minimum and maximum
temperature projected increase was higher for Haramaya than Chiro. The calibration and
evaluation of the DSSAT-SUBSTOR potato model for Haramaya University (Rare field site)
showed good performance for tuber leaf area index (LAI), tuber initiation and tuber yield. The
normalized root mean square error (RMSEn) values for tuber fresh dry yields were less than 20
indicating a good performance of the model. The survey result indicated that 87% of the
respondents perceived the existence of change in climate variables. About 77.6% of the
respondents perceived a decrease in rainfall while 59.4% responded increasing trends in
temperature. During the last 30 years almost 54% of the households perceived a decreasing
trend of potato tuber yield. In connection with this they indicated as the decrease in potato
production was due to climate change. Different adaptation options were used by the
respondents such as water harvesting (61.6%), intensifying use of irrigation (84.3%), change to
a new variety (71.1%), use of soil conservation practices (77.4%), and diversification of crops
(76.1 %). However, lack of information (4.6%), lack of capital (29.8%), lack of water and access
for irrigation (9.2%) affected adaptive capacity of the respondents. Analysis of the impact of
climate change indicated a decrease in potato yield under the future climate by 2030s and 2050s
compared to the baseline period (1980-2017). By 2030s, potato yield was projected to decrease
by 10-12 % under the RCP4.5 emission pathway and by 26-28% under the RCP8.5 emission
pathway. The yield reduction predicted due temperature increase both under the two pathways
and periods could be compensated by the fertilization effect of CO2. An increase in nitrogen level
increased the simulated mean tuber dry yield of potato for all scenarios included in the study.
Hence, increasing nitrogenous fertilizer rate could be considered as one of the potato adaptation
options in the future climate. Therefore, it is concluded that proper choice of adaptation options,
enhancing the awareness of farmers and supporting them with the required credit and inputs
supply mechanisms would help adapt potato to the future climate and reduce the negative
impacts of climate change in the potato growing areas of eastern Ethiopia.