Issue Pack: Cassava value chain in Tanzania – production

Backgrounder

1.      Introduction and how to use this issue pack

This issue pack is designed to provide broadcasters with the information needed to help create effective and entertaining radio programs on cassava. The issue pack focuses on cassava in Tanzania, but much of the information will be relevant to other sub-Saharan African countries where cassava is grown.

The issue pack begins with this introduction, then tells two stories about people in different parts of the cassava value chain.

Section 3 presents information on growing cassava, and about the cassava value chain in Tanzania. Please see Resource Pack 95, Item 9 – An introduction to value chains – for the definition of a “value chain,” and to understand why value chains are important for both broadcasters and farmers.

In section 4, we offer some suggestions on formats to use in creating a program on cassava.

In the final section, we list sources for further information, including resource organizations, online radio programs, online videos, and online documents.

You could use the information in this issue pack in several ways. For example:

• You could use the stories in section 2 as starting points for creating stories in your own area, by interviewing cassava farmers.
• You could use the information in section 3 as background information in any program on cassava.
• You could use the suggestions in section 4 as starting points for creating a cassava program, possibly also using information in section 3 to inform your program.
• You could contact one or more of the organizations mentioned in section 5 for information or for experts to interview.
• You could use the information in the online, audio and video resources in section 5 to help create programs on cassava.

2.      Cassava stories

Mr. Sospeter Njingo, 43, and his wife Faustina William, 31, live in Nyamikoma village, near Mwanza, in northwestern Tanzania. The couple have five healthy young children, two in primary school and three not yet in school. Mr. Njingo has been growing cassava for 15 years. He has five acres of cassava, plus maize, groundnuts, cowpeas and green gram.

Cassava ranks first as a food and cash crop for the couple. Mr. Njingo says it keeps hunger at bay. This season, heavy rains came late and destroyed their maize. Fortunately, the family was able to rely on cassava, though they will have almost none to sell. Mr. Njingo has a message for other farmers: “A farmer who looks down on or undervalues cassava is not yet a farmer.”

The couple face challenges. Because the cassava market is poor, producing a lot means that much ends up rotting. After harvest, prices go down. After three months, storage pests attack stored cassava. Diseases are also a challenge, and more resistant varieties are needed.

Mr. Njingo keeps his own planting materials. He plants in October and harvests in October of the following year. He used to plant a local bitter variety known as Lyongo, but now plants a new sweet variety called Lwabakanga which is more resistant to pests and diseases.

Last year, the family got 20 bags of cassava flour from one acre of cassava. Three bags were for the family and the rest sold for 45,000 Tanzanian shillings each ($28 U.S.) to middlemen. Mr. Njingo used the money to finish constructing his modern house, and was able to attend to some family needs and save a little.

Said Lingano and his wife Salima Ismael have two acres of cassava on their land in Nitekela village, near Mtwara in southeastern Tanzania. Though their cassava yields enough to feed the couple and their four children year round, their post-harvest losses are so high that the family does not have enough to eat. Mr. Lingano sun-dries the cassava and stores it in the kitchen, treating it with smoke. But he finds that 70% of the cassava is spoiled by maize borers.

Mr. Lingano says his family needs information on affordable cassava storage techniques to help them be food secure year round. There are no cassava processing centres in his village. But the family has learned how to make cassava dishes such as bread, cakes, chips and crisps.

He says that, even without processing centres, he could extend the shelf life of his cassava if he knew improved post-harvest management techniques. His plan is to process cassava to earn the income required to sustain his household over the long-term.

3.      Background information on cassava production and the cassava value chain in Tanzania

Cassava production

Cassava is an important food crop in Tanzania, especially in drier areas. More than 80 per cent of Tanzania’s cassava production is used as human food. The remainder is used to feed livestock, make starch, or is exported. Normally, small-scale farmers grow enough for the family, with sometimes a small surplus for sale. Both the roots and the leaves are important for food security in Tanzania.

Cassava was brought to East Africa from its native South America in the 1700s. It is grown in all regions of Tanzania. The main growing areas are: Mtwara, Lindi, Tanga, coastal regions, Zanzibar, Ruvuma, Shinyanga, Mara, Mwanza, and Kigoma.

The flesh of cassava roots (or tubers) is white or yellowish. Cassava roots have a lot of starch, and also contain the nutrients calcium, phosphorus, and vitamin C. The roots have very little protein, but the leaves are a good source of protein. Leaves also contain iron, calcium, vitamin A and vitamin C.

Cassava varieties are categorized as either “sweet” and “bitter.” Bitter varieties contain up to 50 times as much cyanide gas (which must be removed by processing) as sweet varieties. Many farmers, however, prefer bitter varieties because they are high yielding, resistant to pest and diseases, and they repel animals, and thieves.

Because it is drought-tolerant, cassava is sometimes considered a “famine food.” In other words, it reliably provides families with some food even when cereals and other crops fail. During dry periods, the plant stops growing and sheds some older leaves. When moisture is again available, cassava resumes growing and produces new leaves. Cassava has deep roots that find water far down in the soil. Pores on cassava leaves “close up” during dry periods, which reduces water evaporation from the leaves. These qualities allow cassava to survive and yield during dry periods. However, cassava does not like flooding. Submersion in water for a few days or less can destroy a whole crop. In wet soils, cassava yields poorly and is vulnerable to root rot.

Cassava is normally grown during the long rains in Tanzania, with much smaller production in the short rains. Roots can be left underground in the soil for up to three years before harvesting, though older roots are less flavourful, less nutritious, at higher risk of disease, and can be “woody” in texture and fibrous. Because it can be stored in the ground and is drought-tolerant, farmers in almost all regions of Tanzania plant cassava as a back-up in case other crops fail.

When cassava is grown on the same piece of land for a number of years in a row, either by itself or in rotation with other crops, some soil nutrients are reduced. High-yielding cassava varieties can quicken this soil depletion. Using commercial fertilizers or animal manure will increase yields, but these may not be available or affordable. If manure is available, it should be applied when land is prepared for planting. Manure will increase soil fertility, improve soil structure, and the soil’s ability to hold moisture.

Because cassava grows slowly after planting, it is critical to control weeds. Typically, hand pulling weeds requires almost half of the labour involved in growing cassava.

Cassava is often intercropped with crops such as maize, cowpeas, beans, groundnuts, sorghum, bananas (ndizi bukoba), or cashew nuts. According to the Tanzanian Ministry of Agriculture, 40% of cassava acreage is intercropped. The most common reasons for intercropping are: to reduce the risk of a poor harvest, to improve soil fertility, and to control weeds. Intercropping provides the farmer with a variety of food products and sources of income.

Cassava and soil fertility

Infertile soils may be the single most important barrier to high and sustainable cassava yields. But because of the low value of cassava products, farmers may not be able to afford the cost and time required to buy or apply manure or chemical fertilizers.

Most of cassava’s nutrients are in the leaves and stems. If leaves and stems are returned to the soil, the loss of soil nutrients is minimized. In places where leaves and stems are harvested or removed from the field for other reasons, loss of soil nutrients can become a serious concern.

If neither manure nor fertilizers are available, another option is to rotate annually with grain legumes such as beans, lentils, and groundnuts. Intercropping cassava with grain legumes may improve soil fertility, especially if the legumes are well-fertilized and the crop residues returned to the soil. However, it is not possible to get or maintain high yields for long without using fertilizer or manure.

Yield and reasons for low yield

The average cassava yield in Tanzania is about 7-9 tonnes per hectare. Reasons for this low yield include intercropping, the low use of manure and fertilizers, weeds, poor seed, and poor coordination among organizations that are assisting farmers with producing cassava. Late planting also decreases yield. In general, Tanzanian farming families tend to plant cassava late because they concentrate on planting maize, cowpeas, groundnuts and sorghum first, then plant cassava, knowing they will get some yield even when planting late. But since the 1990s, the biggest threat to Tanzania’s cassava production has been diseases and insects.

Also, although cassava is drought-resistant, if it faces serious water shortages in the five months after planting, it loses more than half of its yield. After the fifth month, water shortages do not lead to such heavy losses in yield.

Pest and disease management

To manage cassava diseases, it’s important to use disease-resistant varieties. But the availability of these varieties varies from place to place in Tanzania, and there can be problems meeting demand.

Almost all cassava diseases are spread by planting infected stem cuttings. So it’s important to select clean, disease-free stems. Avoid using stems from plants with discoloured leaves, streaks on the stems, or other signs of disease. Stem cuttings from plants with these symptoms can sprout into diseased seedlings, or not sprout at all.

The two most important cassava diseases in Tanzania are cassava mosaic disease and cassava brown streak disease. To avoid diseases, when chopping stems into stem cuttings for planting, choose the middle brown-skinned portions of the stems. These parts are more likely to sprout into healthy plants than the top green parts of the stem. Also, early planting allows the crop to grow more vigorously and better withstand diseases later in the dry season.

Good farm sanitation helps prevent cassava disease. After harvest, destroy all stems and crop residues that show signs of disease. Clean farm tools before and after tilling to reduce the spread of root rot.

Other general recommendations to reduce disease in cassava are:  

• Choose planting sites with dense vegetation, deep loamy soils, and flat or gently sloping land
• Improve soils by manuring, mulching, and intercropping to encourage vigorous plant health so cassava can tolerate some disease damage

The best way to control pests is to grow a healthy crop of cassava rather than concentrating on killing pest organisms. Identify the main insect and other pests in your area, and choose varieties which tolerate these pests. Some of the most important cassava insect pests – cassava mealybug, cassava green mite, spiraling whitefly (Aleurodicus disperses), and white scale (Aonidomytilus albus) – are spread through infested stem cuttings. Always use clean stem cuttings and reject plant materials infested with stem borne or other kinds of pests.

Also, early planting allows good growth before the dry season when plants are invaded by pests. Cuttings can be treated with insecticides to prevent pests from becoming well-established in a newly planted field, especially in areas where pest populations are large.

Cassava as food

Households typically eat cassava in a variety of forms, including: fresh roots, dried roots, grits (chenga za mihogo) and chips, traditional cassava flour, and cassava leaves.

Fresh roots are often prepared for breakfast, and raw sweet cassava roots are often eaten as a snack between meals. Fresh roots are roasted over an open fire, boiled in water and mixed with coconut juice and beans, or fried in oil. Fresh roots are also dried and stored and known as makopa. These can be stored in the house for later use or sold as grits or chips. Cassava grits or chips are also pounded into traditional cassava flour with a pestle and mortar a few hours before the evening meal.

Cassava leaves (kisamvu) are commonly eaten as a vegetable with stiff cassava porridge (ugali wa muhogo) or rice. Leaves are usually prepared by pounding them into pulp with a pestle and mortar and then boiling in water along with groundnuts and coconut juice or peas. This pounding, washing and boiling process eliminates the poisonous cyanide in the leaves and makes them safe to eat. Methods of processing and preparing the roots also reduce cyanide content and make the roots safe to eat.

Gender and cassava

Cassava is not a men’s crop or a women’s crop. Both men and women are involved in growing cassava, though they tend to specialize in different tasks. Men are ordinarily responsible for land clearing, ploughing and planting, while women specialize in weeding, harvesting, transporting, storage and processing.

If cassava becomes a cash crop, it is likely that women’s and men’s roles will change. From a gender perspective, the impact of turning cassava into a cash crop is difficult to predict. One research study in Tanzania (referenced in document 6 in section 5 below) found that men usually control profits when cassava is grown as a cash crop, while women control small cassava sales and often use the money to buy household needs and pay school costs.

Description of the cassava value chain in Tanzania

The diagram below is a representation of the cassava value chain in Tanzania[1]. It shows that 70% of cassava is consumed at the household (HH) level as fresh roots or processed products such as chips and traditional flour. Thirty per cent of cassava is sold off the farm, with 25% destined for human consumption. Three percent is processed into high-quality cassava flour (HQCF) (used to make food), 1% is made into livestock feed, and 1% made into starch for industrial use.  The left side of the diagram shows the different stages of the cassava value chain.