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Crop Management

Increasingly, sub-Saharan African (SSA) farmers are responding to the decline in cultivable land size due to increasing population by growing more root and tuber crops, which yield more per unit area than grain crops do. Sweetpotato is one of the most widely grown root crops in Sub-Saharan Africa. 

 

The crop is highly tolerant to weeds, growing in poor soils, with relatively few natural enemies, which means that harmful pesticides are rarely used to produce it, and it needs less fertilizer and labor than other crops.It is considered a low labour, low cost and low risk crop which helps families struggling with illness, increasing care requirements and resource losses due to the impact of HIV/AIDS. It is a crop that is predominantly grown by resource poor smallholder farmers, particularly women. 

 

As agriculture becomes more market-oriented in SSA, sweetpotato is one of several crops that farmers can produce to obtain cash income in addition to subsistence food security. Markets for fresh roots and vines do exist but are not yet large. However, with rapid urbanization, it is projected that anticipated food system changes are likely to lead to an increase in demand for fresh roots and value-added sweetpotato-based products. 

 

Sweetpotato roots are a healthy food: all varieties have high levels of vitamins C and E, several B vitamins, iron, zinc, potassium and fiber. The orange-fleshed varieties are very high in pro-vitamin A or beta-carotene, which when eaten is converted into vitamin A. They also have anti-carcinogenic and cardiovascular disease-preventing properties. 

 

There are real opportunities to boost the productivity and utilization of sweetpotato, and investing in this will directly benefit the poor through improving their incomes and nutritional status.

 

 

Since agriculture began farmers have selected, used, exchanged and transported planting materials over short and long distances, and natural selection has also worked on these plants. As a result it is difficult to assemble information on the origin and evolution of agricultural crops, including sweetpotato.

 

Oral and written histories and molecular markers are used to try and trace the origins of different crops. Sweetpotato (Ipomoea batatas (L.) Lam.)  It did not originate in Africa, it was domesticated at least 5,000 years ago in tropical America. Central America is believed to be the centre of origin of sweetpotato, with it being brought to Africa by Portuguese traders in the 16th Century. It was probably introduced on both the east and west coasts of Africa (possibly Angola and Mozambique), and then spread inland. Further introductions from India to East Africa occurred later under British colonial influences. Sweetpotato was already widely grown from Zanzibar to Egypt and used as food and for making beer by the time of the Speke-Grant expedition in the 1860s.

 

Today, sweetpotato is the seventh most important food crop in the world. In 2011, about 8 million of the world's agricultural land was used to grow sweetpotato, and over 95% of the world's sweetpotato output was from developing countries.

 

In Africa, sweetpotato is particularly important in countries surrounding the Great Lakes in East and Central Africa; Malawi, Angola, Mozambique and Madagascar in Southern Africa, and Nigeria in West Africa.

Sweetpotato has the potential to produce remarkably high yields if given the right growing conditions. Sweetpotato can also yield more reliably under unfavourable conditions than many other crops, which is why it is so important for household food security in many places in Sub-Saharan Africa (SSA).

 

Unlike the potato, which is a tuber, or thickened stem, the sweetpotato is a storage root and is vegetatively propagated (sown by vine cuttings rather than seeds). Planting material can be easily and rapidly multiplied from very few roots. 

 

There is ongoing work across the SSA, addressing the best environmental factors that influence sweetpotato production - soil and nutrients, water, light and temperature – with their management, and with production practices that can help to reliably produce good sweetpotato crops.

 

Farmer knowledge of best management practices for sweetpotato may vary between farmers, gender and regions. In most parts of SSA, the gender dimension of land ownership and decision making also plays a role in sweetpotato production and management practices.

Many sweetpotato plants in Sub-Saharan Africa are infested with plant diseases. Fungal and bacterial diseases usually have special resting stages in which the disease organism can survive long periods of time, often in dead leaves, and may be blown in the wind onto young, previously unaffected crops. These resting stages can germinate and penetrate into the new host plant.

 

 Increased sweetpotato production in sub-Saharan Africa is hampered by high incidence of virus diseases.  Sweet potato virus disease (SPVD), caused by synergistic interaction between Sweet potato feathery mottle virus (SPFMV) and Sweet potato chlorotic stunt virus (SPCSV), can cause up to 98% yield losses.  The crop is vegetatively propagated, and so viruses accumulate with each generation, and are difficult to control. Virus disease are usually transmitted through other organisms (vectors), such as whitefly, leafhopper or aphid.

 

In addition, sweetpotato weevil is a major source of economic loss in developing countries. Although the crop can be produced under difficult growing conditions with minimum inputs, weevils continue to plague production. Other sweetpotato pests include nematodes.

 

In order to manage pests and diseases, it is important to know where they come from, how they spread, when they typically arrive and how to recognize and manage them. A lot of work has been done to address the issues of pest and disease management through breeding, production and management practices. Typically, researchers, agronomists and farmers combine a variety of different pest management practices and experiment with these practices to find out which one best suits their unique circumstances.

 

 

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