Improved tree fallows in smallholder maize production in Zambia: do initial testers adopt the technology?

In eastern Zambia, population growth has reduced per-capita land availability to such an extent that traditional bush fallows can no longer be practiced, and low soil fertility is a major constraint to crop production. Improved fallows (IF) based on leguminous trees are a low cash-input agroforestry practice to restore soil fertility. The objective of the study reported here was to assess the adoption of IF by farmers who tested the technology, including the extent to which the technology is practiced relative to its potential scale. The socioeconomic and agroecological determinants of the incidence and scale of adoption are estimated using a two-stage Heckman regression model that corrects for sample selection bias. Seventy-five percent of the testers have adopted the technology, which shows that IF are a suitable practice under conditions of capital scarcity, inadequate access to markets for fertilizer, and relatively low population density, which prevail in large parts of southern Africa. Adopters practice the technology to 42% of its potential scale; a non-linear relationship was found between wealth and the incidence as well as the scale of adoption; land and labor availability limit further expansion. Hence, future on-farm research should emphasize IF options which reduce land and labor requirements such as intercropping IF species with maize, and IF species which can be seeded directly.