Plantains, otherwise known as cooking bananas, are an important food crop in Tanzania and require fertile soil for a good harvest. For around four centuries now, banana-growing land has been enriched by supplements of manure from cattle grazing on nearby pastures.

The strongly increasing population pressure in recent decades has led to a decrease in pastureland and, consequently, manure, causing a reduction in banana harvests. Green manure crops such as herbaceous legumes provide a solution embraced by local farmers, writes Frederick P. Baijukya in his doctorate thesis Adapting to change in banana-based farming systems of northwest Tanzania, which he will be defending on Monday 8 October at Wageningen University.

In his research, Baijukya examined agronomical and socio-economic aspects of the integration of leguminous plants into the agricultural system and reached some encouraging conclusions. His study began with making an inventory of changes in land use via geographical information systems, interviews with local growers and historical documentation. In addition, field tests involving various legume varieties were carried out together with farmers to determine which species were the most suitable.

Local farmers had various reasons for legume cultivation, including weed suppression, increasing harvests and improving the availability of cattle feed. Models were computer-designed, allowing Baijukya to propose optimal solutions tailor-made to the objectives of individual farmers.

As a consequence of evolutions in the agricultural system, the role of livestock has also changed. Traditional free-ranging cattle are increasingly being replaced by dairy stock (crossed with Dutch varieties) that stay in sheds all year round. The cattle are mostly fed food crop remains, and their manure is used for soil improvement.

The agricultural system in Tanzania can be compared to the traditional farming on sandy soils in the Dutch province of Drenthe. Originally infertile, the soils here were also enriched by man in order to become suitable for farming.

According to Baijukya, local farmers view green manure and fodder crops with favour, and there is already a large demand for legume seeds. His research has generated new practical insights that will provide solutions for a sustainable continuation of traditional banana cultivation in Tanzania.

Research into the role of legumes in African agriculture will be expanded within the framework of the EU project AfricaNUANCES, and Baijukya's study will be extended to eight African countries.

Frederick P. Baijukya will defend his thesis Adapting to change in banana-based farming systems of northwest Tanzania on 8 October 2004 at 16.00 in the assembly hall of Wageningen University at Generaal Foulkesweg 1a in Wageningen.