The Temporal-spatial Variation And Tendency Analysis Of Staple Crop Water Requirement In Ethiopia

Ethiopia, which depends mainly on rain-fed agriculture, is one of the countries suffering most vulnerable impact to climate change. In this study, Penman-Monteith method recommended by the United Nations Food and Agriculture Organization(FAO) was used to calculate the staple crop water requirement in Ethiopia. Based on 20 meteorological stations data in Ethiopia, we analysed the temporal-spatial distribution of crops water requirement of teff(Eragrostis tef), maize(Zea mays) and wheat(Triticum aestivum Linn.) from 2002 to 2009 as a means of geographic information system(GIS). The conclusions are following:(1) Ethiopa is becoming warming and drying from 2002 to 2009 overall. In the low altitude area, the warming and drying trends in crop growing season are the most intense, the trends in non-growing season is moderate, while warming and drying trends of growing season in high-altitude region is the weakest.(2) The growth period of teff in Ethiopia is short, about 85 days. At the initial and development stages, it coincides with the heavey rainy season and abundant rainfall can basically meet the crop water requirement. Mid-season and late-season stages are critical to the growth of teff, land area which crop water deficit reaches over 50% is more than half region of Ethiopia. Suitable planting areas for teff, such as Afar, Tigray, Amhara and parts of Oromia Region, are becoming more arid. Therefore, these areas should be increased irrigation practices, in order to compensate for teff water deficit at mid-season and late-season stages.(3) The initial stage of maize coincides with the shorter rainy season in Ethiopia, and crop water requirement is not its growth restrictions. At the development stage, the radio of land areas which crop water deficit is 50%-80% reaches the maximum of 23.37%, while the radio of no water deficit areas reaches the minimum of 27.70% through the whole growing season of maize. So the development stage is the limited period of maize growth. Especially in the Tigray, Amhara and east of Oromia Region should be supplemented for irrigation. Only Somali and southeastern part of Oromia Region are arid at mid-season and late-season stages, while in rest of lands, precipitation during heavy rainy season can meet the demand of crop water requirement for maize.(4) The precipitation in most parts of Ethiopia is larger than that of crop water requirement during the initial and development stages of wheat. Until the mid-season stage, the amount of precipitation can not meet the water demand of wheat. However, the late-season stage of wheat is the dry season in Ethiopia. The proportion of no water deficit zone decline to minimize(11.64%), while the proportion of water deficit >80% region has reached the highest(41.89%). The area of crop water deficit <35% has been reduced to the southwest corner of Ethiopia while it is in most parts of the country during the initial stage, so it is particularly important to supplement irrigation at the late-season stage of wheat.In summary, mid-season and late-season stages of teff, development stage of maize, late-season stage of wheat are the critical periods to their crop water requirements, respectively. Irrigation at these stages should be increased to make up for their crop water deficit.