Opportunities for and constraints to adoption of improved fallows: ICRAF's experience in the humid tropics of Cameroon

Food crop production in highly populated areas of the African humid tropics is increasingly faced by problems of soil fertility with declining crop yields and higher incidence of weeds reported. Between 1988 and 1998, ICRAF has developed two improved fallow technologies using a fanner participatory approach. The first technology, a rotational tree fallow with Calliandra calothyrsus, has been proven to increase crop yields provided farmers cut back at 0.05 m above ground level and prune the trees twice during cropping. In addition to soil fertility improvement, Calliandra calothyrsus fallows have many additional short-term benefits that, if properly promoted, can accelerate adoption: reducing weeds, providing fuel wood and stakes and forming excellent apiaries as the calliandra trees flower almost all year round. However, the following constraints are likely to hamper the adoption of tree fallows by certain farmer categories: (1) trees occupy the land permanently, (2) tree management is often incompatible with current cropping system, (3) soil fertility improvement is only observed after a number of years. Therefore, a shrub fallow was designed, using Cajanus cajan in a relay cropping system. Farmers' response to this technology was positive. Benefits reported were higher crop yields, easier clearing of cajanus fallows, and the shading out of weeds by the shrubs. Women particularly appreciated the technology for its low labour demand and because these shrubs can be planted on land with less secure tenure. However, wider dissemination of tree and shrub fallows has been slowed down by lack of a targeted extension approach and adequate seed supply strategies, which should be based on joint efforts between farmers, extensionists, the private seed sector and farmers.