Cassava production trends and land area expansion in Tanzania had been fluctuating over a period of years. In all major cassava production zones the production declined from 1985/86 to 1988/89 except in the Eastern zone where cassava production increased(Figure 2). Other zones Eke, the Western, Central, Northern and Southern Highlands experienced low and almost constant production (Appendix 1). There was an increase in production in the season of 1989/1990 in all zones except eastern. The highest cassava production was reported in Southern zone in the season 1991/92, and it was over 750,000 tons of dried cassava chips. This was followed by decline of production in the subsequent seasons. The changes in production are reflected very well in the land area under cassava especially in the areas where extensive farming is practised. Обучение за рубежом учеба за рубежом обучение.
The area under cassava in most of the zones declined from 1985/86 to 1988/89 except Southern zone where a slight increase was observed. In all zones the area under cassava was fluctuating over seasons. Also cassava yields which is a measure for productivity has been fluctuating with season,
the highest yield was observed in Eastern zone in 1985/86 and 1989/90 which was almost 4.5 tons/ha. In the subsequent seasons, the zone recorded low yields, probably due to the outbreak of cassava mealybugs. The only zone which indicated increase in yield was the Central zone. The estimated yields by the national statistics department are far below than the average of 10.5 t/ha recorded during the countrywide study by the Collaborative Study of Cassava in Africa (COSCA) project between 1989 to 1992 (COSCA Tanzania, 1996). Also FAO information shows that the national average yield in Tanzania was 10.4 t/ha in 1991. The disparity in the yield estimates might be due to numerous difficulties encountered during these studies. therefore at country level very few farm level studies have included yield measurements for cassava. The interpretation of these records should put these into account.
Cassava with major competing crops.
Estimates of production of other food staples in the country namely maize, Paddy and millets/sorghums are presented in Table 1. The annual production figures for the period from 1986/87 to 1995/96 showed that the highest annual mean production of 2151.3 millions tomes per
Source: Planning and Marketing Division. Ministry of agriculture and Cooperatives, Dar es Salaarn, T
Appendix 2 shows the trend in production of major food crops. In the countrywide survey by COSCA, the farmers groups interviewed in the 45 representative villages indicated that cassava land area was increasing in about 50% of the villages. The majopr crops considered to be replacing cassava are maize, and Paddy and where cassava land area was reported to be
increasing it was replacing pasture. The major Factors reported to be affecting cassava production and Increase in land area are disease Incidences particularly cassava brown streak virus (CBSd) and cassava mosaic disease(CMD). Also pests mainly cassava grew mites (CGD and cassava mealybug (CM) [Table 2].
Table 2. Percentage distribution of villages which reported decreasing cassava land area by reasons for the decrease
|Reason for decrease in land arm||Percentage distribution of villages|
|Shortage of planting material||6|
|Preferred crops available||6|
Of the disease and pests mentioned, CGM was the most wide spread, This was observed in more than 90% of the representative villages (COSCA Tanzania, 1996).
Cassava is an important subsistence food crop in the semi-arid areas and sometimes considered as a famine reserve when cereals fail due to its drought tolerance, and the fact that the roots can readily be stored under the ground (Department of Research and Training, 1991). Studies conducted by COSCA project b etween 1989 and 1992 showed that cassava in Tanzania is used in chips/flour form in most villages, and in fresh form and alcoholic beverages in a relatively few villages (COSCA Tanzania, 1996).
Africawide, cassava roots are used in a wide range of forms of food products which can be grouped into fresh roots (unprocessed), granules, pastes, chips/fiour, starch etc
Analysis of the information on the farmers rank of three major cassava products showed that the range of the products is low in Tanzania where more than 90% of the representative villages reported that their most important cassava product was chips/flour (Table 3). Other products reported as being of primary importance were starch, alcohol and fresh (unprocessed) roots (COSCA Tanzania, 1996). Cooked paste was reported in one village but as of secondary importance.
In the few areas that use cassava root in fresh form cassava was grown in 50% of the staple land. These are pen-urban areas which supply the cities with fresh cassava roots. Where cassava roots were used for alcoholic beverages or staidi, cassava was found in an average of 35% of staple land area.
These two cassava products are produced for sale rather than for home consumption- In contrast, cassava chips/flour is used more for home consumption than for sale. Cassava chips production for export is however a growing activity particularly in the Southern zone of Tanzania (COSCA, 1996).
Cassava leaves are also used both in fresh and processed form. Succulent cassava leaves are crushed or pounded and boiled/cooked before eating. For processing, cassava leaves can be sundried for 3 to 5 days to get a local vegetable known as 'sansa' (Tanznia Department of Research and Training, 1991). This is a processed form of cassava leaves common in areas around Lake Victoria.Table 3. Percentage distribution of representative villages by most widely used cassava food product, all representative countries compared with Tanzania
|Percentage distribution of villages|
* Starch accounts for 1%
Source: COSCA Tanzania, 1996
These include manufacture of livestock feeds and industrial starch. In livestock feeds a small percentage of processed cassava is utilized in domestic animal feeds. In 1985 the Tanzania Animal Feeds Company used dry cassava in feeds for poultry and pigs (MALD, 1987). The poultry feeds contained 5% to 10% cassava flour and the feeds for pigs contained 20% cassava
flour (Msabaha et al 1986). The manufacturing of such cassava based feeds was however, stopped because it was expensive when compared to meal based substitutes. Industrial processed cassava starch was produced by the Tanzania Starch Company located at Sengerema Mwanza in 1984. The Factory had a capacity of producing 40 tons of wet cassava or 15 tons of dry cassava per day WILD, 1987) but was closed down in early 1990's due to shortage of fresh roots (raw materials). Plans are underway to reestablish it in Dar-es, Salaam with the assurance of raw materials from the cassava farms owned by the starch Factory
COSCA surveys showed that there were some attempts particularly in Tanga region, eastern zone for farmers to extract starch locally. Tins starch was part of the 1% in other cassava products mentioned in the surveyed villages.
Cassava green mites (Mononychellus sp.) were first reported in the country in 1972 at Ukerewe islands (Msabaha, 1990). At present cassava green mites have spread throughout the country. Studies to establish the distribution of different mite species were initiated in collaboration with the International Institute of Tropical Agriculture (IITA) in Nigeria and the International Centre for Insect Physiology (ICIPE) in Kenya. It was noted that mite population density is highest during the driest periods; and high humidity conditions tends to suppress major outbreaks and damage (Msabaha, 1990). Estimated losses in yield of cassava roots in Tanzania vary from 50% to 80% (Shukla, 1976) depending on the susceptibility of cassava varieties.
Cultural control measures such as early planting, intercropping with other crops, and use of NPK fertilizers appeared not effective in controlling the green mites. While breeding programmes for host-plant resistance or tolerance to cassava green mite are in progress. There are good chances for the development of resistant cultivars as several clones showing resistance to green mites have been idenfified and mechanism of resistance studied.
Todate the national root and tuber crops improvement programme, has selected some few varieties namely: Alpin valenca, Ali Mtumba, Liongo, Kwimba, Msitu Zanzibar, Kibaha, Kigoma-red and Maparigano that show moderate resistance to the pest. These are being multiplied under proper sanitation technique so as to generate enough planting material for farmers. The experiences under multiplication tasks will be highlighted in the coming sections.
Surveys undertaken recently between 1992 and 1993 to establish the distribution of CMD in the country showed that, CMD is widely distributed all over the country with much incidence along the coastal belt of Indian ocean and the Lake zone. The two areas mentioned above have higher CMD may be due to long establishment of the crop (Raya el al 1993). These two areas are the major cassava producing areas in the country with long history of cassava cultivation.
Another reason of the persistence of the disease is due to the continuous use of affected planting materials by farmers It was noted that CMD is mostly tramsnitted through cutting infection (81%) and only 19% by whitefly vector (Raya et al 1993). Surveys conducted throughout the major growing areas by COSCA showed that CMD was next to cassava green mite in spreadits symptoms were observed in about 70% of the villages (COSCA Tanzania 1996)[Table 4]. As of recent the East African Cassava Mosaic Disease (EACMD) was found distributed along the coastal belt of Indian Ocean and the Lake zone (Ogbe el al 1996).
CBSD incidences were observed along the coast of indian ocean particularly in Mtwara and Lindi regions. As of recent tins disease has spread to the coast region. The disease is more devastating because heavy attack by CBSD can result into high magnitude yield loss and storage root quality.
For cassava bacterial blight (CBB) the disease is sporadic in nature. In Tanzania, the disease was very much widely distributed in the 1970' s (Nyango, 1990). CBB appeared to be widely spread in the lake victoria zone this necessitated to set up quarantine measures to stop movement of planting material from these areas to other parts of the country.
For all major three diseases the following are being done to contain these major diseases
(i) Host - plant resistance
(ii) Cultural practices
(iii) Regulatory control/Sanitation measures
There are other diseases attacking cassava in the field but are not of economic importance. These include brown leaf spots (Cercospora henningsii), white leaf spot (Phaeramularia manihots) and blight leaf spots (Cercospora vicosea).
Table 4. Incidence and severity of cassava plant pests/diseases
|% Villages1||% Landraces2||Number3||score4|
|Cassava green mites||92||51||157||1.3|
|African cassava mosaic||72||27||83||1.3|
|Cassava bacterial blight||23||7||22||1.1|
1- Percartage of 39 villages where problem was observed.
2- Percent of 308 landraces assessed infected/infested
3- Number of landraces infected /infested,
4- On a 14 scale
Source: COSCA Tanzania, 1996.
Cassava is known to be an easy crop to cultivate. Most farmers thus tend not to manage the crop properly (Masabaha, 1988). Most of the time, cassava is planted into exhausted soils. Recent studies have established that infertile sods produce cassava storage roots yields less by 40% and the same trend was observed in cassava shoot yield (Roots Tubers Annual report, 1994). In areas where crop rotation cycle is practised, usually cassava is grown at the end of the cycle, when the soils have already been exhausted.
Late planting of the cassava crop is also a problem, even though cassava is drought tolerant relative to other arable crops. Studies done have shown that cassava planted earlier yields higher than that planted late. Unweeded cassava crop, especially when in monoculture is a constraint to increased cassava yields. Work done on weed management in the 1970' s indicated that if weeding was not done within the first two months, there was a 70% reduction in yield. One hand weeding only at one month after planting gave 3 1 of the expected yield (TARO, 1983).
Lack of adequate planting materials is another constraint to expanding cassava land area. There is no institution in Tanzania responsible for multiplication and distribution of the improved varieties of cassava (Msabaha, 1988). Consequently farmers plant any materials they come across. Most of the varieties grown by farmers have been selected mainly on their characteristics. Most of such varieties have low genetic potential for yields/or resistance to the major pests and diseases.
Recent studies by COSCA have revealed that shortage of planting materials is generally a constraint in dry areas where biomass production is usually low in comparison with moist areas; and when new materials such as improved varieties are being introduced for the first time (COSCA Tanzania, 1996). This is because multiplication rate is low in comparison with crops such as grains propagated by seeds. This problem has also been accelerated by lack of irrigation facilities at the stations where multiplication is being done. This has contributed to tremendous loss of many materials particularly during the dry period and also it makes it impossible to multiply cassava planting materials for the future use.
There is limited knowledge of the extension personnel shortage of extension personnel, topped with severe logistical problems in most regions where cassava is grown. Inadequate transport, makes it impossible for the extensionist to cover a number of villages. Poor farmer - research extension linkages and lack of integrated research approach have sometimes led researchers to come up with messages which are not farmer problem oriented. Tins ultimately leads to low adoption rate of extension messages (Lema and Hemskeerk, 1996). Even when researchers want fully involvement of extensionists in transfer of technology, but meagre resources do not allow for this.
Low level of interaction between researchers and extension agents has also contributed to the farmers' lack of improved varieties. Presently however, research-extension linkages have been emphasized, and there has been bimonthly workshops between researchers and extensionists.
Under the National Agriculture and Livestock Extension Rehabilitation Project, some logistical support has been provided in some regions. However it is still not adequate to fulfil the requirements of executing extension workload.
limited transport and storage facilities makes access to market a problem (Masabaha, 1990). Both local and external markets for cassava are available, however due to bulk nature of the crop, farmers are obliged to sell their cassava at nearby markets mainly at reduced prices. Roads to producing areas mostly not good (Appendix 5)
In COSCA studies it was noted that the cassava production cash income was higher in villages which had easy access to markets or to production credit (COSCA Tanzania, 1996). Farmer who had my access to market earned more cash because they had greater access to market demands for the products. Also the same farmers earned more cash from cassava because they had greater access to supply of inputs which -enabled them to expand production. A farmer produces a crop with a purchased inputs orgy if he is able to earn cash to recover his cash expenditure on the production of the crop.
Ile preferred crops available was cited as a reason for declining cassava land area in T a (COSCA,Tanzania. 1996). A crop can be preferred if it is available in a form which the housewife finds it convenient to prepare into food. Cassava is not a homogenous food product. it is transformed into several products during processing which vary in taste, texture, and particularly in convenience.
The main cassava product processed in most cassava growing zones is cassava chips/flour. This product is not able to compete effectively with food grains such as maize and rice in the market.
During the COSCA studies-, it was shown that in the areas where cassava was reported to be dechning, cassava was mostly being replaced by various cereal grams. These grams included maize which was in 36% among the villages surveyed, rice was in 22%, sorghum and millet was in 21%, sweet potato was in 7% and cotton was in 17% (COSCA Tanzania, 1996).
Data from the COSCA study, show that almost all the villages which processed cassava into convenient food products reported expanding cassava land area. The use of the unproved postharvest handling facilities expanded market demand because it improved product quality.
Quality processed cassava products are more convenient to urban consumers and are more competitive with food grains in the market. Easy access to market centres did not make as much impact on the cassava land area expansion as the improved, post harvest handling practices.
Farmers would be able to expand cassava land area under conditions of difficult access to market centres. provided improved processing technologies were available.
Lack of diversified cassava products in Tanzania have very much hindered the widespread uffization of cassava in the country. The cassava flour obtained as the final product after milling or pounding the chips is only consumed as! ugali. The recent research advances on the improvement of processing techniques and diversified uses of cassava flours into cakes, chinchin and doughnuts might increase the demand of cassava in urban areas where there is an assured market.
The recent introduction of the low-cost storage technology for fresh cassava roots in some arm to extend the shelf life of the roots for urban consumers will also contribute positively to increased utilization of cassava.