The Cassava Transformation: Africa's Best-Kept Secret

Chapter 6. Agronomic Practices

CHAPTER 6 Agronomic Practices Introduction We have shown in chapter 5 that the development of high-yielding cassava varieties represents a powerful but incomplete engine of growth of the cassava industry. Ultimately, the adoption and spread of high-yielding varieties will be influenced by the development of improved agronomic practices and labor-saving harvesting technology. This chapter draws on the COSCA findings to discuss the evolution of the following agronomic practices: length of fallow period; quality of planting material, plant density (plant spacing) and planting date; cropping pattern (intercropping or mono-cropping); labor use; and cassava harvesting. The analyses in this chapter will show that farmers adopt profitable agronomic practices that save labor. The chapter also shows that progressive farmers who are adopting improved agronomic practices need labor-saving harvesting technology because production and harvesting labor bottlenecks are limiting the amount of cassava farmers are able to produce. 85 The Cassava Transformation Three Types of Fallow Systems There are three main types of fallow systems in Africa. The first is long fallow and it refers to fewer than ten years of continuous cultivation followed by ten or more years of fallow. The second type, short fallow, is fewer than ten years of continuous cultivation followed by fewer than ten years of fallow between crops. The third type, continuous cultivation, refers to at least ten years of continuous cropping. An average of 4 percent of the cassava fields surveyed in the six COSCA study countries were under the long fallow system, 79 percent were under short fallow, and 17 percent were under continuous cultivation (table 6.1). • long Fallow System When population density was low, long fallow was common and there was no guarantee that farmers would return to the original farmed area after a definite period oftime (Okigbo 1984). The COSCA study found that cassava cultivation under the long fallow system has declined in all six study countries because of population growth. In each COSCA study country, farmers reported that they believed that most of their fields would recover soil fertility in ten years or fewer of fallow. • Short Fallow System Data from the six COSCA study countries show that farmers produce cassava under short-fallow system for a variety of reasons, among them are cassava's long growth period, pest and disease problems, and compatibility with crops grown in association with cassava. Pest and disease infestations increase with repeated cultivation of cassava in the same field in most environments. The COSCA study found that under high population pressure on land, farmers produce cassava under short fallow in order to break the pest and disease cycles when the problems are serious. For example, Kazimzumbwi village in the coastal strip along the Indian Ocean in Tanzania is characterized by a high population density (ninety-six persons per square kilometer) and good road access to markets where cassava is sold. Yet farmers in the Kazimzumbwi village practice cassava production under the short fallow system because of 86 Agronomic Practices Table B.1. Percentage of Fields of Different Crops under Different Fallow System: Average for Six COSCA Study Countries. Source: COSCA Study. CROP LONG FALLOW Cassava 4 Yam 14 Rice 2 Beans (or peas) 10 Sweet potato 0 Average 5 SHORT CONTINUOUS FALLOW CULTIVATION PERCENTAGE 79 17 82 4 69 29 66 24 62 38 75 20 TOTAL 100 100 100 100 100 100 serious problems with the cassava mosaic disease and green mite. Cassava is intercropped with beans and maize. The three crops are planted in November, with maize being harvested three months after planting, beans six months after planting, and cassava twelve months after planting because of high market demand due to high population density and easy access to markets. The field is left in fallow for twelve months to break the cycles of the mosaic disease and green mite. In West Africa, cassava is often grown in association with yam, which requires fertile soil. Farmers in high population density areas who grow cassava in association with yam adopt a short fallow system.' Cassava production in Nimbo, a village in Eastern Nigeria, is an example of cassava and yam production under short fallow. The village is characterized by high population density (one hundred persons per square kilometer); a market center that is visited regularly by cassava middlemen (traders and processors); and mild attacks of cassava pests and diseases. In Nimbo, yam, maize, and melon are planted in April and...