3    The resource base and production systems

3.1 Physical and climatic features

3.2 Physiography, soils, land and water resources

3.3 Economy and production systems

It has been shown in the conceptual framework that outcomes at a point in time in terms of productivity, natural resource conditions and human welfare are based on the past resource base and their use by households and communities in response to market, policy and other rules and norms. Therefore, the natural resource base and production systems in the Oromiya region are described briefly to provide the context for understanding the problems of land degradation, its evolution and causes.

3.1 Physical and climatic features

Oromiya region is located in the central part of Ethiopia extending from 3°20' N to 10°35' N and from 34°05' E to 43°11' E with a total land area of 353,690 km² (Figure 2). It constitutes about 31.15% of the total land size of the country making it the largest of all the regions. The region is divided into 12 administrative zones and 180 woredas (annaas).

Figure 2. Regional State of Oromiya (including agro-ecological zones).

The region has common borders with six national regional states, Sudan and Kenya. It shares the longest border (1860 km) with the Southern Peoples' Nation and Nationalities Regional State followed by the Somali Regional State (1410 km) (see Figure 2).

Oromiya region's topography consists of a high and rugged central plateau and the peripheral lowlands. From a topographic point of view, the region can be divided into three parts namely:

The Eastern Plateau: This part of the region, which also includes the associated lowlands, gradually slopes down from the edge of the eastern escarpment of the Rift Valley and extends to the Somalia region. The administrative zones of West Hararghe, East Hararghe, Bale, Arsi and Borana are included in this plateau.

The Rift Valley: This is part of the Great African Rift Valley extending from Jordan in the north through Ethiopia, Kenya and Tanzania to Mozambique in the south.

The Western Plateau: This part of Oromiya region extends westwards from the edge of the western escarpment of the Rift Valley to Benishangul and Gambella regions. This area is made up of a wide plateau, mountains of medium height dissected by the Awash, Baro, Gibe and Abay rivers and their associated tributaries. North Shewa, West Shewa, East Wellega, West Wellega, Illubabor and Jimma zones are included here (Berhanu et al. 1998a).

Elevations in the region range from less than 500 to over 4300 meters above sea level (masl). The highest plateau includes mountains such as Batu in Bale (4377 masl), Kaka in Arsi (4245 masl), Chilalo in Arsi (4170 masl), Arba Guna in Arsi (3625 masl), Mul'ata in Hararghe (3405 masl), Selalle in North Shewa (3544 masl), and Wenchi in West Shewa (3387 masl). The highest mountains are concentrated on the Eastern Plateau of the region.

The highlands (>1500 masl) constitute about 48% of the region's total area while areas between 1000 to 1500 masl constitute 38% (OBPED 1997a). The highlands are home to more than 80% of the total human population and 70% of the livestock population of the region and account for over 90% of the cropland. Almost 90% of the region's economic activities are concentrated in the highlands (Haile-Yesus 1996).

In terms of climate, highlands in the region are cool and the lowlands are warm. The most prevalent agro-climatic conditions in the highlands, although there are considerable variations from locality to locality, are tepid to cool temperature and moist to sub-humid humidity. The lowlands have a semi-arid to arid climate (Berhanu et al. 1998a).

Spring (March–May) and summer (June–August) are periods of high solar radiation. However, in the western flank and highland portion of the eastern flank, because of high humidity and frequent cloud cover, temperatures are lower in summer. Spring is the warmest season with May being the warmest. Autumn (September–November) and winter (December–February) are seasons of relatively low sunshine with cool winds from the northern hemisphere reducing temperatures in winter with December being the coldest month (Berhanu et al. 1998a). In general, temperature is inversely related to elevation: the mean annual temperature in the highlands is between 10°C and 22°C, while it is between 22°C and 30°C in the lowlands.

The major rainy season extends from June to September and covers most parts of the region while October to May is normally dry. However, an entirely different atmospheric circulation system takes place in some parts of the region during March and April when the East African low-pressure system moves south and pulls moisture-bearing winds from the Indian Ocean which induces some precipitation. These small rains are sufficient for the 'belg' crops in some areas and are a relief from the long dry season in other areas. This characteristic seasonality in the rainfall distribution pattern needs the classification of its regimes based on the designation of a month to be either rainy or dry. ¹ Furthermore, the whole region is grouped in two rainfall regimes: Rainfall regime 1 is characterised by one rainy season with only one dry season. The number of rainy months varies from 7 to 10. It is the type of rainfall, which characterises part of the Rift Valley and the whole western flank of Oromiya. Rainfall regime 2 is characterised by two rainy seasons (double maximum). It characterises the areas in the eastern flank of Oromiya in which the number of rainy months varies from 5 to 8 (Table 1).

1. This classification involves the calculation of the rainfall coefficients for each month for selected representative stations. The rainfall coefficient is the ratio between the mean monthly rainfall and one twelfth of the annual mean. Those with rainfall coefficients of 0.6 and above are categorised as rainy and the rest as dry (OBPED 1997b).

Table 1. Rainfall regimes in Oromiya region.

Reliability of rainfall is important in the region because the livelihood for the rural population is based mainly on rain-fed agriculture. In general, the annual average amount of rainfall decreases from west to east. The highest amount is in Gore (2122 mm), while the lowest is in the eastern border area (200 mm). This annual pattern is about 70% and 30% reliable in the highlands and lowlands, respectively (OBPED 1997b).

3.2 Physiography, soils, land and water resources

The major physiographic divisions of tectonic structures in the region that resulted from past geologic activities are summarised in Table 2. About one-half is covered by laval highlands and massifs. Ancient crystalline rocks cover about 24% of the region: 13% in the highlands of north-western Borana and central South Bale and 11% in the lowlands of south-western Borana.

Table 2. Physiographic divisions of tectonic structures of Oromiya region.

In general, there are 21 main soil units recognised in the region (Table 3). The major soil groupings in the region are Vertisols, Nitosols, Luvisols, Acrisols, Cambisols and Phaeozems. Each of these has properties, to be discussed later, that affect soil degradation differently.

Table 3. Major soil types, their area coverage and distribution in Oromiya region.

Out of the total land area of 353,690 km², vegetation cover accounts for 67.5%, while cultivated land accounts for 29.5%. Grassland, water bodies, urban and built up areas and wastelands constitute the rest (Table 4). The land use pattern varies significantly across zones due to differences in physiographic conditions and population density. Over time, cultivated area has increased while other types of land like forest and bush land have decreased.

Table 4. Land use pattern by zone in the Oromiya region, 1993.

The climatic condition of the region results in high precipitation during the rains which in turn causes stream flows. However, as precipitation is seasonal, the volume of discharge of rivers is also subject to seasonal fluctuations. There are seven major drainage basins in the region, the largest being Genale covering 32% of the area followed by WabiShebelle (21%) and Blue Nile (16%). High rainfall in the highlands also results in high runoff. Annual run off rates vary from under 50 cm/h to over 600 cm/h (Table 5).

Table 5. Annual runoff in the Oromiya region.

Preliminary estimates by water resources master plan studies conducted for twelve basins show that there is 2.9 billion cubic m of ground water resources in Ethiopia. Out of this, 2.0 billion cubic m is within the Oromiya region. The region is also endowed with large quantities of surface water capable of producing large amounts of electricity and able to irrigate vast areas of land. The source for most of the hydroelectric power generated in Ethiopia are the following rivers in the region: Qoqa, Fincha'a, Malka-Wakena and Gilgel Gibe. Out of the total of about 377 MW of hydropower currently produced in the country, 366 MW is produced in Oromiya region. There are several naturally occurring lakes and man-made reservoirs of variable sizes and irrigation potential. Some of the lakes are Zuway, Langano, Shala, Abiyata, Haro Maya, Wancii, Abbaya, Bushoftu, Hora, Fincha'a, Qoqa and Gafarsa. The irrigation potential of the region, suitable for large-scale development, is estimated at about 800 thousand hectares, though only 7% of the potential has been developed and is in use (Berhanu et al. 1998a).

3.3 Economy and production systems

Oromiya region has predominantly an agrarian economy. Agriculture, services and industry account for about 70%, 24% and 6% of the regional GDP, respectively. Also, these sectors account for 92.2%, 6.5% and 1.3% of employment, respectively. The region accounts for about 51% of the total major crop production in Ethiopia and is considered the source of the country's agricultural surplus. It is also the major source of food supply for the country's major urban centres and deficit areas. Oromiya also produces 63% of the national exports and is a major source of raw materials for domestic industries (Berhanu et al. 1998a).

The region is generally divided into three main zones according to agricultural production potential which is based on agro-climate, soil and production systems: high potential cereal zone, low potential cereal zone and perennial zone (Figure 2). Out of 146 highland woredas in the region, 93 are located in the high potential cereal zone, 18 in the low potential cereal zone and 35 in the perennial zone. Forty-four woredas, including most located in low potential areas, have recently been identified as food insecure and there is widespread malnutrition and chronic food insecurity in many rural areas of the region.

Within each zone there are various subsystems of production but there are two broad categories: The mixed crop–livestock farming system and the pastoralist system. Oromiya region has the largest livestock resource base in Ethiopia. Cattle, sheep, goats, donkeys and camels are the major types of animals reared and there are about 18.8 million tropical livestock units (TLU) in the region. The mixed crop–livestock farming system of the highlands carries 70% of the total livestock resource base while the remaining 30% is owned by pastoralists in the arid and semi-arid lowlands. Pastoralists of the lowlands almost totally depend on livestock. They are a multipurpose resource providing draught power and manure for crop production and food (meat, milk, butter and cheese) and other by-products and are also the principal form of saving. Livestock also provide manure for fuel and serve as a living bank and insurance during crop failure. At medium to high altitudes (>500 masl), about 90% of crop production is carried out by using draught power (Berhanu et al. 1998a).

The mixed crop–livestock farming system can be further divided into four sub production systems. These systems (discussed below) have implications for how the land resource is used and the resulting effects on degradation.

• The enset–coffee–cereal–livestock production system: This production system occurs along the Wolliso to Jimma region. Coffee and enset are grown in home gardens at altitudes below 2200 masl while on the main fields are planted cereals. Enset is the main food crop in the system. Maize and sorghum are the main cereals followed by teff, wheat and barley. Pulses (haricot and lima beans) are grown as garden crops. Prominent root crops are taro, yam, and sweet potato. Although crop rotation (alternating cereals with pulses) is practised, legumes cover about 11% of crop area. Fertiliser use is also low. Fallowing is practised on hilly and extensively cultivated parts where population pressure is lower. Crop residues from teff, sorghum, maize and enset are used as fodder.
• The forest coffee–enset–cereal–livestock production system: This production system is practised in parts of Jimma zone and in the highlands of Borana. Enset is grown in home gardens and cereals on fields. Coffee is normally grown under shade trees in the forest. The forest undergrowth is occasionally cleared as an agronomic practice to promote coffee growth and development. The coffee plants are mostly wild but with selection and management some improvement is taking place. The rainfall is as high as 2200 mm and the region has a bimodal rainfall pattern.The most important cereal crops are maize, sorghum, teff and millet. The importance of cereals is less compared to that under the enset–coffee–cereal–livestock production system. Pulses include haricot and faba beans, chickpeas, lentils and pigeon peas. Oil crops include noug, linseed, rape seed and castor beans. Some vegetables, root and tuber crops and spices are also grown. Fallowing and crop rotation are practised and cattle manure is mainly used for crops grown in the home gardens (enset, maize etc.). Fertiliser use and other soil conservation practices are not common, and crop residues are used as fencing and cementing materials. Cultivation is mainly with hoes and ox ploughing is limited because of widespread trypanosomosis.
• The mixed cereal–livestock production system: This is the prevalent production system in almost all zones in the region. Among the crops, teff covers the largest area (31%), followed by wheat (18%), maize and sorghum (11%), barley (8%), oats and finger millets (5%), pulses (10%), oil crops (6.5%) and other crops (10.5%). In Hararghe, in areas such as Garamuleta and Chercher, inter-cropping is widely practised. Beans are usually mixed with crops such as sorghum and maize, and chat fields are inter-cropped with sweet potato. Ox ploughing is prevalent in these parts of Hararghe although hand ploughing, locally called dongora culture, is practised by certain groups of farmers in preparing land with either steep slopes, stones or wood stumps. Farmers practice dongora often in groups. Fallowing is not practised under this production system and soil fertility is traditionally maintained through crop rotation (cereals with pulses). Chemical fertiliser application is common in Shewa and Arsi zones but not in other areas. Terracing is practised on the hilly slopes of the eastern and north-eastern highlands of the region. Crop residues are used as fodder, construction material and fuel.
• The barley–wheat–livestock production system: Arsi, Bale, East Wellega and North Shewa zones practice this production system. Compared to the mixed cereal–livestock production system, this one is generally practised at slightly higher altitudes. The crops grown include barley, wheat, oats, faba beans, field peas, lentils and oil crops with barley covering about 54% of the total production area. Home gardening is not common except for rape seed and maize. The temperature in the regions which practice this system limits the number of crop types grown. Ox ploughing is more common than hoe culture. Fallowing is practised the area. Soil fertility is maintained through crop rotation and the use of cow dung as manure is minimal due to the high dependence of the communities on it for fuel. The use of chemical fertilisers is not common except in some parts of Shewa and Arsi. Crop residues are used as fodder, construction material and fuel.