Nzega district is among seven districts of Tabora region. Most parts of the district are located in the northern part of Tabora region, shares borders with Shinyanga rural district in the North, Uyui district in the South, Kahama district to the West and Igunga district on the eastern side. In terms of international identification, the district lies between latitudes 3045’ and 5000’ South of the Equator and between longitudes 32030’ and 33030’ east of Greenwich.
Land Area, Land Use Pattern and Administrative Units
Nzega district has a total land area of 6,961 sq. kms most of which is a rolling plain with very few small hills and escarpments. The land available for agricultural production is 6,343 sq. kms. Out of this arable land of the district, an average of 1,600 sq. kms is cultivated annually, leaving 5,361 sq. kms of useable and unusable land due to rock outcrops and other reasons such as poor soil fertility, soil erosion, river beds and human settlements. About 4,296 sq. kms are either forest reserves or natural forest while land used for grazing covers about 1,065 sq. kms.
Administratively, Nzega District is divided into 4 divisions and 37 wards with a total of 151 villages and 1,010 hamlets distributed unevenly . Nyasa division covers about 33.0 percent of total land area of the district followed by Puge division with about 22.9 percent. Mwakalundi division has the smallest land area in the district constituting only 21.5 percent of the total land area. Bukene division accounts for 22.6 percent of total land area.
Topography, Soils and Climate
The district forms part of the Central Plateau of Tanzania which is relatively homogeneous with gently undulating plains intersected by seasonally flooded valleybottoms. In the extreme north east this pattern gives way to open flat land suitable for cultivation and covered by well or moderately drained soils of sandy loam texture.
The soils vary from red lateritic earth grey sand to silt hardpan and iron crust mbuga as shown below:
Rock and very Shallow Soils – These are mostly found on hills with steep slopes though also used for cultivation they are very susceptible to erosion and suitable ideally for grazing and fuel wood production. These soils are found in Itobo, Mizibaziba, Mwakanshahala and Semembela wards;
Well – Drained Sandy Soils – Their soil texture is sandy and loamy or coarser within 100 cm of the surface, easily leached and therefore of little intrinsic fertility. They are found in Ikindwa, Shigamba, Mwamala, Mwangoye, Miguwa, Isanzu, Ijanija, Utwigu and Mbogwe wards;
Well – Drained Medium Mixture Soils – Soil colour ranges from red to yellow loamy sand and or clay loam. The soils have greater ability to retain nutrients and therefore are of better potential for agriculture, but need more water. They are found in Puge, Nkiniziwa, Ndala, Karitu, Kasela, Itilo, Tongi, Isanzu and Itobo wards;
Black Clay Soils – These soils are calcareous, which develop cracks on drying and about half are sodic with high fertility and are most suitable for cotton. They are found in Mwakashanhala, Nata, Mbogwe, Miguha, Lusu, Mwangoye and Mwamala wards;
Upland Soils with Impeded Drainage – These soils are easily saturated with water within 100cm of the surface long enough to restrict the range of crops that can be grown. Their textures range from sand to sandy clay, suitable for paddy production. They are to be found in Mogwa, Kahamanhalaga and Igusule wards; and
Mbuga Soils – Mbuga soils include all types of soil in areas where the water table is within 100cm from the surface, which can cause flooding during wet season. They range from sand to clay, of which sandy clay loam and clay are prominent. They are found in Lusu, Nata, Wela, Isanzu, Muhugi, Miguwa, Tongi and Ndala wards. Other places are Mwakanshahala, Ikindwa, Semembela, Igusule and Mwamala wards.
Although the majority of these soils have good nutrient content and are considered suitable for a wide range of food and cash crops and therefore have the potential for profitable cultivation, Nzega district soils can at best be described as moderately fertile.
The district receives rainfall of between 650mm and 1,200mm annually, falling between the months of October or November and December and a dry period from January to February/March and a second lower peak occurring soon after the dry spell is over in February or March and the rains then tail off in April/May
Nzega district forms part of the vast central plateau of Tabora region, an area of flat and gently undulating plains broken in places by prominent hills. Most parts of the district lie between 1,100 meters and 1,300 meters above sea level and form the main watershed separating rivers flowing north eastward into the Manonga River and the Wembere Swamps. The district harbours the second largest basin in the region, that of the Manonga river and Wembere Swamp, draining ultimately into Lake Eyasi.
Agro – Ecological Zones (AEZ)
Basically the district has two distinctive agro - ecological zones, namely, the High Rainfall Zone and the Low Rainfall Zone.
The High Rainfall Zone
This zone covers the western part of the district in parts of Bukene division and to the north parts of Puge division. The terrain of the zone is low lying used successfully for paddy cultivation and has been the paddy producing area of the district. A small part of this zone has good tobacco growing potential, while on the north of the zone is suitable for cotton growing. Soils are sandy loam and alluvial. This zone being about 100 percent tsetse fly – free area is good range land and hence cattle’s rearing in this area is popular. The main food crops grown in this zone are maize, paddy, groundnuts and cassava. Cotton and paddy are grown as cash crops.
The Low Rainfall Zone
This zone lies in the central, northeast and southeast part of Nzega district and is covered with alluvial soils. It covers Mwakalundi and Nyasa division and part of Bukene and Puge division. The zone has low rainfall of between 450mm and 850mm and hence limits maize yields leaving groundnuts and paddy as the major cash crops. Cattle rearing is practised in this zone as it is a 100 percent tsetse-free area.
Temperatures range from 28oC to 30oC. The highest temperatures are experienced in October just before the onset of rainfall. Temperatures fall gradually to December and thereafter remain relatively constant up to May. From May to August the district experiences low temperatures.
Nzega district is covered by miombo woodland, acacia woodland and grassland. The miombo woodland is natural forest for the district which is found in Bukene division and some parts of Mwakalundi division. Miombo woodlands are associated with well drained soils on high ground while acacia woodlands and grasslands thrive in low lying areas of some impeded drainage.
Population Size and Growth
Over the years the population of Nzega District has grown significantly. According to the 2002 Population and Housing Census the district had 415,203 people compared to 296,082 inhabitants counted in 1988 Population Census resulting in a big increase of 119,121 people or an average annual growth rate of 2.5 percent during intercensal period down from 2.8 percent of the previous intercensal period of 1978 to 1988. Inspite of its high growth rate Nzega had the least rate of growth among the districts of Tabora region during the 1988 to 2002 period. The projections for 2009 put the district population at 529,234, out of which, females accounted for 51.1 percent of the population. Table 1.3 shows the population size and its growth for Tabora region and its districts for the 1988 and 2002 population censuses.
Compared to other districts of Tabora region, Nzega district is the second smallest rural district in terms of land area but was the most populous rural district at the time of the 2002 population census. Accordingly, the district contributed the highest share of the regional population at 28.5 percent in 1988 and 24.3 percent at the time of the 2002 Population and Housing Census. Between 1988 and 2002 the district’s population grew at an average annual growth rate of 2.5 percent compared to the regional growth rate of 3.6 percent and national average growth rate of 2.4 percent.
Nzega district, with an average population density of 43 and 60 persons per sq. km in 1988 and 2002 respectively, is the most densely populated rural district of Tabora region. The regional average population density was 14 and 22 persons per sq. km. in 1988 and 2002 respectively. It is logical that as the population increases so will population density because the district’s land area is inelastic.