Abstract

Agro-climatic characterization of western Oromia was performed using indigenous knowledge and historical meteorological data indices in a statistical software. Rainfall and temperature of selected meteorological stations representing different Agro-ecological zones (lowland, midland and highland) of western Oromia were analyzed on annual, seasonal and monthly time scales using long period data. Quantitative data were analyzed through SPSS and qualitative data through content analysis. Instant Statistical Packages for Agro-climatological data was used in analyzing the 30 years meteorological data of western Oromia meteorological stations. This study looks at growing season dates in terms of dry spell lengths, onset, cessation and length of growing season among others using INSTAT software. The spatial distributions of different annual and seasonal rainfall variables were mapped. A survey research design was used, and data collected through focus group discussions, questionnaires and key informant interviews. Simple random and purposive sampling methods were used, where 210 small scale farmers and 30 key informants from western Oromia participated. The study conducted surveys of 210 households in the selected woredas of Western Oromia to characterize the agro climate of smallholder farmers. Rainfall, minimum temperature and maximum temperature data of western Oromia (1980-2014) were analyzed to assess agro-climatic characterization and climatic trend of the area. The rainfall and temperature data over the western Oromia are analyzed on an annual basis using historical datasets. Over western Oromia, the observed average total annual rainfall showed a significant decreasing trend (43.67 mm per decade) in the last 30 years analysis period, with a relatively large inter-annual variability, while the maximum, mean and minimum temperatures have increased at a rate of 0.22°C and 0.21 8°C per decade, respectively. The study revealed that most significant change has been unpredictable rains (60.48%), very hot season (20.95%) and prolonged drought (14.29%). The historical climate results across the selected stations shown that a late start has an early end of rainfall hence a short growing season observed. Farmers’ perceived late on set of rain, poor distribution within the season, and sometimes early cessation. Local community perceived the onset date of Kiremt (Ganna) rainfall of study area was on the first week of May and the cessation date of Kiremt rainfall starting from the last week of November over the last 20 years. But, the historical climate results show the onset date of the growing season was in the early June and the cessation date of Kiremt rainfall on the mid October. Therefore, Knowledge on the date of onset and cessation rains and length of growing period (LGP) will help to plan the agricultural operations better, particularly, land preparation and sowing.

Keywords: Agro climate; Characterization; Indigenous knowledge; Growing season; Historical climate