Analysis of historical rainfall data and associated risks on rain-fed tef production at Debre Zeit, central Ethiopia

Abstract

As drought is the major bottleneck for the rain fed tef (Eragrostis tef) production, developing workable strategy that can mitigate its impacts is mandatory. To draw this strategy knowledge on how the rainfall behaves in the past decades is important. The central theme for this paper is studying the rainfall behavior over the past six decades in relation to the major rainfall induced risks for the rain-fed “tef” production system using 59 years of rainfall data. Risk of dry spell during germination and flowering is computed whereas crop water requirement satisfaction index is generated using water balance approach. The study shows strong intra annual ariation but no trend on the annual and monthly mean rainfall totals, and number of rain days. The existence of this intra annual variation has enabled a wide range of possible planting dates that runs from late June to late August and there was no indication of trend that the planting date has a tendency to be either later or earlier in recent years. The result also depicts once in five years early and once in nine years late onset of the rain. Existence of these wide range of possible planting dates, early and late onset of the rain, high intra year variability in rainfall amount and number of rain days and absence of any apparent trend on the rainfall amount and number of rain days may shed some light how farmers are now facing frequent extremes that may consequence frequent crop failures. This signifies the need for every year rainfall forecasts and their appropriate analysis to have successful planting as well to minimize related risks and consequently to have better and consistent production system.

Keywords: Start of the rain, Planting dates, Dry spell, LGP, CWSI, End of the season