POTENTIAL IMPACTS OF CLIMATE CHANGE ON POTATO (Solanum tuberosum L.) PRODUCTION AND ADAPTATION OPTIONS IN EASTERN ETHIOPIA

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 xxiii 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.