Africa is rich in both natural and human resources, yet nearly 200 million of its people are undernourished because of inadequate food supplies. Comprehensive strategies are needed across the continent to harness the power of science and technology (S&T) in ways that boost agricultural productivity, profitability, and sustainability -- ultimately ensuring that all Africans have access to enough safe and nutritious food to meet their dietary needs. This report addresses the question of how science and technology can be mobilized to make that promise a reality.
Diversified systems have been thoroughly studied in the past, but there has been no concerted effort to systematically exploit their potential benefits. Addressing these issues along the lines of the production ecological framework may offer new insights that will further enhance the obvious benefits of mixed intercropping (Box 4.13).
An appealing effort to this end is the integrated approach of maize-soybean cultivation in the Northern Guinea Savannah. Over the past 10 years breeders have produced the so-called dual-purpose soybean for maize cropping systems. They developed soybean varieties that produce a higher biomass in addition to good grain yields, fixing higher amounts of nitrogen. The soybean lines now available can produce about 2.5 tonnes of grains and 2.5-3 tonnes of forage per hectare, and there is every indication that further progress can be made. Farmers are starting to reap the benefits from maize-soybean rotations that systematically address the various aspects of production ecology.
A successful combination of intercropping is maize with pigeonpea or cowpea (promising drought-tolerant legumes that thrive on residual moisture). Both legumes can be successfully cultivated with maize, without significant compromise on yield. While both crops are sown simultaneously, the legumes start to grow only after the maize is harvested. Research in Malawi shows that pigeonpea and maize can grow sequentially in the same row, rather than in separate rows. The combination of legumes with cereals also shows increased fertilizer-nitrogren use efficiency (Mapfuno and Giller, 2001).
Refocusing breeding strategies may even lead to a complete change in farming systems. During the 1970s and 1980s, cowpea breeders sought high-yielding grain varieties. This strategy did not succeed as farmers rejected the new cultivars, due to severe attacks from various pests. The past decade has seen development of dual-purpose cowpeas, producing higher amounts of both grain and fodder. These varieties have affected agricultural intensification through crop-livestock integration in the dry savanna regions of West and Central Africa. Cowpea fodder as a supplemental feed increases animal weight during the dry season, with up to 50 kilograms of extra meat per annum from animals in some instances. Over 300 kilograms per hectare more cereal grain can be obtained as a result of improved soil fertility gained directly from the cowpea and from more and better quality of manure from the animals. The better-fed ruminants also give more milk and provide stronger traction, resulting in more and timely land preparation and better crop yields (Brader, 2002).
Box 4.14 illustrates that while the introduction of new technologies may be beneficial to some groups, it may unintentionally adversely affect others (see also Bernus et Pouillon, 1990).