Tanzania - FAO wheat database

Wheat production potential in Tanzania

Tanzania's population is about 20 m and nine tenths of the people depend on agriculture, directly or indirectly, for their livelihood. The inhospitably long dry season, and the infestation of large areas with tsetse fly, restrict two thirds of the population to one tenth of the area of the country. Tanzania's economy is, and will continue to b e , agricultural. Since 1970, however, food production has expanded at a rate of only 2.9 percent, while the population has grown at a rate of 3.3 percent annually. During this period, Tanzania has changed from a net exporter of food to a net importer on a large scale.

Climate

Tanzania is situated between latitudes 1 0 S and 11 0 S , and between longitudes 30 E and 43 E. Since it is so close to the equator, Tanzania has a typically tropical climate in all lowland areas, with warm temperatures, slow wind velocities, humid air in most months., and no winter. Altitude modifies the climate of the highlands to a temperature regime suitable for wheat. In the south-east the climate is warmed by the Indian Ocean.

In the east and south-east annual rainfall generally ranges between 750 mm and 1,250 mm. Some parts of the Southern Highlands receive more than 1,250 mm. Large areas in central and southern Tanzania receive much less than 750 mm of rainfall. Rainfall increases towards the west and north, and parts of the Northern Highlands receive more than 1,250 mm.

Mean monthly temperatures for January range between 20 0 C and 26 0 C, coolest in the Northern and -Southern Highlands and warmest along the coast of the Indian Ocean. The range of mean monthly temperatures for July is between 16 0 C and 220C.

In much of Tanzania, lack of water limits the growing of wheat more than temperature. Under the prevailing conditions of temperature, sunshine and wind, the minimum annual rainfall required for wheat is 750 mm. The following tables give the proportions of the total area of the country receiving various amounts of rainfall.

Percentage of total area
Annual rainfall with a 90 percent probability over 10 years
32

47

18

3

less than 500 mm

500-750 mm

750-1,250 mm

over 1,250 mm

[Source: FAO, 1976]

The total land area of Tanzania is estimated at 88.6 m ha. The area with sufficient rainfall (more than 750 mm per year) for reliable crop production is thus about 18.6 m ha. The total area harvested during 1979/80 was 6.3 m ha, while potential arable land (regardless of rainfall) has been estimated at 28 m ha. Thus '-he potential for the development of rainfed crop production, including wheat, to sustain the growing rural population, is satisfactory.

Soils

Soils with medium to high potential are found mostly in the highland and plateau regions of Mbeya, Njombe, Iringa, Rukwa, Kigoma, Tabora, Kagera, Shinyanga, Mwanza, Singida, Dodoma, Kilimanjaro, Meru and the Usambaras. The level to gently undulating terrain of these areas favours cultivation, but this very feature is often associated with flooding, inadequate drainage and saline soils. These soils cover an area of about 8 m ha.

Soils of slight to medium fertility, with moderate potential, cover considerable areas in most regions. Another group of soils, which are infertile but have moderate potential when fertilized, is fairly extensive in central and south-eastern Tanzania. Together these two groups of soils occupy about 20 m ha.

Wheat production in Tanzania depends almost entirely on rainfall. At present, only 144,000 ha are under partial or full-scale irrigation. Potential irrigable land is estimated at 933,000 ha.

Present wheat production

Wheat is grown entirely under rainfed conditions. Production falls short of requirements and the country relies heavily on wheat import, which ranged between 47,000 and 76,000 tons between 1982 and 1984.

Wheat is the preferred food grain in towns, while the rural population lives mainly on other cereals. As people move into the towns, consumption of wheat in the coming years is likely to grow faster than that of all other cerals. Evidently, unless a determined effort is undertaken in the research and development of wheat, Tanzania's wheat production will remain inadequate for a long time.

There are three modes of wheat production in Tanzania, each with a different level of technical management:

(1) Large-scale mechanized production is being carried out by the National Food and Agriculture Corporation (NAFCO) with the assistance of the Canadian International Development Agency in the Arusha and Kilimajaro regions. Since 1970 these agencies have established six farms totalling 20,757 ha in the Hanang Wheat Complex in the Arusha region . in addition, NAFCO has 6,000 ha under wheat in the Kilimajaro region. Wheat cultivation on these farms is fully mechanized and average yield is 1.6 tons/ha without the use of fertilizer. Erosion problems at Hanang are discussed below in Chapter 7 , item 15. To conserve water in the soil and to prevent erosion, the technique of minimum tillage is now being practised, using chisel and sweep ploughs. About three quarters of Tanzania's commercial wheat production comes from these farms.

(2) Small- to medium-scale mechanized wheat cultivation has been practised in parts of the Arusha and Kilimanjaro regions, and in the Irenga region, since 1945. Medium-sized wheat estates, established by expatriate (British) farmers, still continue under state management. Alongside these estates, small-scale farmers grow wheat, hiring tractors and combine harvesters from specialist local contractors.

(3) Hand-tool cultivated wheat is traditional in parts of the Southern Highlands in the Iringa and Mbeya regions. The average plot is a quarter of a hectare. Growers use no input other than seeds and family labour, and they consume practically all that they harvest. Tanzania's evolving rural development programme may improve the output of small-scale wheat farming.

Production potential

All areas below an 0 altitude of 1,500 m experience temperatures above 20 C for most of the possible growing period and are, therefore, not suitable for wheat. Annual precipitation in these areas may appear to be adequate, but the amounts received during the season when wheat would be grown (April to October) are small and erratic. Areas above 1,500 m are relatively cool, have more reliable precipitation and offer good prospects for rainfed wheat production.

Land with potential for wheat is delineated in seven mapping units:

Land with medium potential (P2)

P2c. Potential limited by climate. This land has no limitation except that temperatures are too warm to achieve large wheat yields.

Three fifths of this mapping unit consist of nearly level to gently undulating land with deep, brown, medium-textured soils (chromic, eutric and calcic cambisols). A quarter of the mapping unit consists of deep, dark-coloured, clayey soils with a fair amount of organic matter and a good surface structure (pellic vertisols) and brownish-coloured, clayey soils, containing little organic matter but with a medium-textured surface (chromic vertisols). These soils, together constituting some 85 percent of this mapping unit, are moderately suitable (P2c) f or wheat . The remaining 15 percent of the unit has very shallow, gravelly soils (lithosols) which have no potential (N) for wheat production.

P2h. Potential limited by hard pans. This mapping unit occupies nearly level to undulating plateaux, about four fifths of which have deep, medium-textured soils with hard lime layers at shallow depths (petrocalcic phases of calcic cambisols, eutric cambisols and eutric nitosols). The hard layers occurring in these soils restrict aeration and the penetration of plant roots. In about a third of these soils, the hard pans are fairly deep and the soils are moderately suitable (P2h) for wheat. In the remaining part, mostly where the surface is undulating, the pans occur near the surface so that any attempt to improve the land, such as by levelling or terracing, would be likely to expose tha pans; this difficulty renders the land unsuitable (N) for wheat.

The remaining fith of the mapping unit comprises deep, dark-coloured, clayey soils containing a moderate amount of organic matter (pellic vertisols); shallow., medium-textured soils with hard pans just below the plough layer (eutric planosols); shallow. dark-coloured, steep soils containing much organic matter and lime (rendzinas); and very shallow S 0 11 S (lithosols). The vertisols are moderately suitable (P2c) and the others unsuitable (N) for wheat production even with a high level of inputs.

P2e. Potential limited by erosion risks. Half this mapping unit (not counting the enclaves near Mbeya in south-west Tanzania, and Arusha in the north-east) consists of gently sloping to steeply dissected. reddish, medium-to fine-textured soils (haplic, eutric and dystric nitosols).

A fifth of the unit consists, in almost equal proportions, of brownish, medium-textured soils (eutric and calcic cambisols) and black to greyish-brown volcanic ash soils (humic and ochric andosols). Two fifths of all these have a small risk of soil erosion and have moderate potential (P2e) for wheat. Three fifths have a medium to severe erosion risk, and small to no potential (P3/N).

Some 15 percent of this mapping unit is covered by strongly leached, reddish-brown to dark red acidic soils (orthic and ferric acrisols) which have a low potential (P3s) for wheat production. The remaining 15 percent comprises dark-coloured, clayey soils (pellic vertisols), imperfectly-drained soils (gleysols), organic soils (histosols) and very shallow soils (lithosols), of which the vertisols have a moderate potential (P2c) while the others have no potential (N) for wheat.

About three fifths of the area of the enclaves near Mbeya and Arusha have steeply dissected topography and medium- to fine-textured, black volcanic ash soils, containing much organic matter (mollic andosols). These soils are very fertile, but are mostly unsuitable (N) for wheat because of their steep slopes, except for limited areas where potential would be large (P1) after terracing. A quarter of the land in the enclaves has gentle slopes and deep, reddish-coloured soils (eutric nitosols). These soils have a medium risk of erosion and a medium potential (P2e) f or wheat. . The remaining 15 percent of the area has very shallow soils (lithosols) with no potential (N) for wheat production.

P2s. Potential limited by infertile soils. Half this mapping unit has nearly level to undulating terrain with leached, reddish-brown to dark red soils (ferric acrisols, rhodic ferralsols and ferric luvisols), which are poor in nutrients and have medium to low potential (P2s, P3s and P 2 s , respectively).

About 30 percent of the mapping unit has reddish-brown soils with an iron pan at shallow depths (plinthic acrisols). These soils have a limited rooting depth and are infertile, and thus either marginally suitable or unsuitable (P3h/N) for wheat.

The remaining fifth of the mapping unit has deep, reddish-brown soils (eutric nitosols), imperfectly-drained soils with an iron pan at shallow depths (plinthic gleysols) and dark-coloured, clayey soils (pellic vertisols) which have medium (P2c), no (N) and moderate (P2c) potential, respectively.

Land with low potential (P3)

P3e. Potential limited by erosion risks. This mapping unit occurs in an area with plentiful rainfall and an undulating to steeply dissected landform. Erosion risks are severe. Three fifths of it have medium- to fine-textured, leached, reddish-coloured soils that contain much iron (ferric acrisols). one third of these soils has an iron pan at shallow depth (plinthic acrisols). None of the acrisols are very fertile, and the erosion risks moderate to severe. One third of them occupy relatively gentle slopes and have low potential (P3e) for wheat, while the rest are unsuitable (N).

About 15 percent o f t he unit consists o f imperfectly-drained soils with an iron pan at shallow depths (plinthic gleysols) while the remaining quarter of the unit has very sandy soils containing much iron (ferralic arenosols). These soils are not suitable (N) for wheat production.

P3t. Potential limited by stony soils. Seven tenths of this mapping unit are consist chiefly of undulating to steeply dissected land with brown, medium-textured, gravelly and stony soils (chromic cambisols/dystric regosols). Their main constraint is that stones in the surface soil hinder cultural operations. They are also subject to medium to severe risks of erosion. one tenth of their extent, however, is not too stony or gravelly, and has a low potential (P3t) for wheat. The remaining part has no potential.

One tenth of the mapping unit has deeply leached, reddish-coloured, fine-textured soils (orthic acrisols) with iron pans at shallow depths in places (plinthic acrisols); they have small to no potential (P3s and P3h/N respectively) for wheat.

The remaining fifth of this mapping unit has very shallow soils (lithosols) that. have no potential (N) for wheat production.

P3h. Potential limited by hard pans. Three quarters of this mapping unit have nearly level to undulating terrain with storngly leached, reddish-coloured, medium-textured soils and very hard pans at shallow depths (duripan phases of orthic, ferric and plinthic acrisols). These soils are not very fertile, and the hard pans restrict water movement and the penetration of plant roots. In a third of this area the pans are not too close to the surface and the soils are marginally suitable (P3h) for wheat; the rest have no potential (N) because the pans are close to the surface.

The remaining quarter of the mapping unit is occupied by different soils which include highly weathered, sandy soils containing much iron (ferralic arenosols), river-deposited, stratified soils (fluvisols), imperfectly-drained soils ( pellic vertisols) These soils have no (N) and moderate (P2c) potential respectively for wheat production.

Tanzania: land potential sub-classes by mapping unit in '000 ha.
Designation
Description
Extent
Land potential sub-class
Extent
P2c
Land with medium potential, limited by climate
190
P2c

N

160

30

P2h
Land with medium potential, limited by hard pans
412
P2h

P3c

N

111

21

280

P2e
Land with medium potential, limited by erosion risks
1 923
P2e

P2c

P3s

P1

N

654

96

180

192

801

P2s
Land with low potential, limited by einfertile soils
687
P2s

P3s

P2c

P3h

N

227

116

96

103

145

P3e
Land with low potential, limited by erosion risks
692
P3e

N

138

554

P3t
Land with low potential, limited by stony soils
2 931
P3t

P3s

N

205

146

2 580

P3h
Land with low potential, limited by hard pans
182
P3h

P2c

N

45

21

116

Land with no potential (N)

This class of land comprises all parts of Tanzania below an altitude of 1,500 m, which are too warm for wheat, and all areas with soils that are not suitable for rainfed wheat production.

Concluding remarks

In general, the regions of Tanzania in which wheat could be produced are known. However detailed soil investigations are urgently needed within these regions, to select suitable areas for extending wheat cultivation.

Research on wheat in Tanzania is at present concerned mainly with large-scale, mechanized production. This research is necessary but. an over-dependence on machinery also limills the expansion of the crop. Intermediate methods of production which might be u s e f u 1 to small- and medium-scale producers, should also be investigated. For this purpose, research at Uyole Agricultural Centre, near Mbeya, should be strengthened.

There has in the past been a long period of small and unchanging producer prices for wheat. Although this is over and producer prices have increased in recent years, they should continue to be adjusted regularly, taking into account the cost of production and the prices of alternative crops.

Finally Government should recognize that such inputs as electric power, seed, fertilizer and pesticides, and access to agricultural credit, marketing and transport, are vitally important components of any policy for crop improvement.

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