Sesbania sesban improved fallows in eastern Zambia: Their inception, development and farmer enthusiasm

In eastern Zambia, nitrogen deficiency is a major limiting factor for incre ased food production. Soil fertility has been declining because of nearly c ontinuous maize (Zea mays) cultivation with little or no nutrient inputs. T he use of short-duration tree fallows was one of several agroforestry optio ns hypothesized to restore soil fertility. Sesbania sesban, an indigenous N -2-fixing tree was the most promising among species tested in screening tri als. Several studies since 1987 have demonstrated the dramatic potential of two- or three-year sesbania fallows in restoring soil fertility and increa sing maize yields. Analyses showed that these improved fallow systems were feasible, profitable, and acceptable to farmers. Results suggest that high maize yields following fallows are primarily due to improved N input and av ailability by the fallows. The potential to increase maize production witho ut applying mineral fertilizers has excited thousands of farmers who are en thusiastically participating in the evaluation of this technology. The numb er of farmers who are testing a range of improved fallow practices has incr eased from 200 in 1994 to over 3000 in 1997. Presently, a strong network of institutions comprising government, NGOs, development projects, and farmer organizations is facilitating the adaptive research and expansion of impro ved fallow technology in eastern Zambia. Key elements in the research proce ss that contributed to the achievements are effective diagnosis of farmers' problems, building on farmers' indigenous knowledge, generating several di fferent fallow options for farmers to test, ex-ante economic analysis, farm er participation in on-farm trials, and development of a network for adapti ve research and dissemination.