Trend of Growing Season Characteristics of Semi-Arid Arusha District in Tanzania

The timing and distribution of rainfall determine both the length and quality of the growing season, and hence have important implications for agricultural production and food security. Using over 50 years of climatic data for Arusha District in Tanzania, the paper presents an analysis of growing season characteristics and other meteorological variables. Results indicate that the climate of Arusha District and Oljoro in particular is changing. Both the length of the growing season and number of wet days within the season are showing a decreasing trend as rains appear to be starting later than they used to in the past. Other meteorological variables such as temperature, wind speed and reference evapotranspiration are showing an increasing trend. Changes in land use/cover in and around the study area in the 1970s through 1990s due to expansion of agricultural land and population pressure would seem to have fuelled the observed changes in the growing season characteristics. This does not augur well for rain-fed agriculture and thus judicial use of scarce water resources including rainwater harvesting would seem to be a viable option for sustainable agricultural production.