Monitoring N-leaching and exploring coffee farmers' adaptation strategies to higher N-fertilizers price in Costa Rica

Slash-and-burn agriculture (S&B) is the leading factor behind the degradation of tropical forests and represents an ecological and economic dead end. Many authors have noted that this system is very difficult to improve without the support of public policy. In dryland Africa, especially in Niger and northern Cameroon, grants funded by projects and through levies on profits from bundled cotton sales have made it possible to support the conservation of young trees on fields when fallows are cleared and during weeding. This Assisted Natural Regeneration (ANR) support policy was promoted by the state corporation responsible for the development of cotton crops and was accompanied by a delimitation and demarcation of fields. From 1990 to the present, this policy has resulted in the conservation of over one million Faidherbia albida, and, in so doing, the expansion and densification of agroforestry parklands. In the equatorial wetland, of D R Congo, the experience is much more recent. Simple Management Plans of village territories were put in place since 2010 to secure rural land tenure. ANR methods have also been promoted to conserve young trees growing spontaneously in cultivated fields, after S&B, when fallows are cleared and during weeding. In areas where environment was too degraded, leguminous trees have been planted using taungya method. Trees conserved or planted improve fallow productivity in terms of firewood and other forest products, accelerate the restoration of soil fertility and block the invasion of savanna pyrophytic vegetation, before a new 'slash-and- charcoal' cycle. Over 150 farmers have used ANR and 1700 ha of Acacia auriculiformis have been planted. The use of simple techniques requiring little labour or inputs, associated with land tenure security policies, allows a gradual transition from S&B to more productive and sustainable agroforestry systems (parklands in the Sahel and improved fallow in forest areas). (Résumé d'auteur