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Evolution of soil and water conservation strategies ‐‐ Towards land husbandry Volume 15, issue 1, JANVIER-FÉVRIER-MARS 2004

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Institut de recherche pour le développement (IRD), Réseau Érosion BP 64501, 34394 Montpellier cedex 5 <roosempl.ird.fr>

Faced with the damages caused to the environment as a result of erosion, man has long tried to reduce them through traditional strategies adapted to land pressure and geared to improving water control for a better soil fertility and productivity. The fact that they have been dropped does not mean that these strategies are not efficient, but simply that they are no longer adapted to today‘s socio‐economic conditions. From the mid‐1850s onwards, centralised governments started sending their engineers to the countryside with a view to reduce the damages to the quality of the water and to industrial or urban equipments erosion brought in its stride. Parallel to a series of economic and ecological crises, agricultural hydraulic equipment strategies were gradually designed : soil restoration in mountain terrains (RTM, restauration des terrains de montagne) in 1850, in the Alps and the Pyrenees ; soil and water conservation (SWC) during the 1930 Great Plain crisis in the United States ; and soil and defence restoration (DRS, défense et restauration des sols), from 1940 to 1980 in the mountains of the Mediterranean. Analysing the various reasons for the failure of SWC‐based projects, the Porto Rico workshop of 1987 pointed out to the non‐involvement of the farmers in the decision‐making process as well as to the inefficiency of the techniques proposed to improve soil productivity. A new strategy (land husbandry) was proposed that would better take into account the vital problems of the farmers, i.e. how to survive while making the best possible use of land and labour. To soil conservationists, this was a revolution entailing a redefinition of priorities : i) first of all, improve the management of the « best » land to increase farmers‘ benefits and then deal with the « bad » lands which produce most of the sediments ; ii) second, initiate a participative approach bringing together technicians and farmers, right from the beginning of a project, so as to find out how farmers perceive erosion problems and how these can be best dealt with ; iii) develop new farming systems for a more cost‐effective and more sustainable water, biomass, and soil fertilily management ; iv) let government‐appointed specialists tackle catastrophic erosion damages (torrential gullies, landslides, floods and river control) while letting farmers be responsible for improving the rural environment. As a conclusion to this paper, the evolution of erosion control techniques in Africa from the colonial period till the « Man & Erosion » Colloquium held in 2000 in Yaoundé, is presented. Research has demonstrated the tremendously negative impact of sheet erosion on topsoil fertility, but it has also shown the possibility to restore and even improve soil productivity using simple techniques such as direct drilling under litter or under leguminous cover. Organic matter control must be complemented by mineral nutrient to be combined with SWC techniques in order to enhance soil and labour productivity.