Rainfall is the most important element that limits the productivity of crops. Proper analysis of rainfall trend and understanding of its relationship with land productivity may help in planning purposes. Accordingly, a study was conducted to assess the statistical behavior of monthly, seasonal and annual rainfall in south west Ethiopia (Arba Minch). Furthermore, correlation statistics was employed to explain the relationship between land productivity and the pattern of rainfall for two major crops (teff and maize). The analysis for recent rainfall data (2005 to 2016) showed that the mean annual total rainfall was 962 mm, where the highest was recorded in 2007 (1,141 mm), and the least was in 2009 (638 mm). Similarly, the mean total rainfall for the short and main rainy seasons were 373 and 417 mm, respectively. The main rainy season (June to October) covered nearly 42% of the total rainfall and 39% of the annual rainfall was recorded during the short rainy season (March to May). With respect to the variability of the rainfall record, the short rainy season was more unpredictable than both (which had 34% coefficient of variation), the main rainy season and the total annual rainfall (26 and 15% in their respective orders). The nature of the variability is in agreement with the rest locations in the country, where in most cases, the total annual rainfall is expectable. The correlation analysis revealed that maize productivity had strong positive relationship with the rainfall record of the main and short rainy season, while teff negatively correlated with the distribution of the rainfall during 2011 and 2016. Similarly, rainfall during the month of June had high correlation (0.76) with the yield of teff, while for the same crop, the total rainfall for the month of September had equal negative correlation with the productivity (0.78).
Key words: Coefficient of variation, correlation, land productivity, rainfall, trend.
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