Programs to develop the traditional livestock farming of the Sahel have often been ineffective despite great human and financial contributions. Efforts directed at better pasture and herd management, pasture improvement. livestock fattening, and increased marketing, have failed to improve the overall productivity of the herds and to stop range deterioration. A major reason is that many of ophy that the problems have to be solved primarily by preventing overgrazing, since at present the climate cannot be influenced and irrigation can only be used locally. Smaller herds and the development of areas of nonuse (wells). in addition to improvement of the herd composition and animal health, will improve the output of livestock farming. Future good management of the rangeSummary. Results of a Malian-Dutch research project on the Sahelian pastures and their utilization suggest reasons why some efforts to develop traditional livestock farming in this area have been unsuccessful. Failure to appreciate the effects of low soil fertility as well as low rainfall on pasture production has tesulted in underestimation of the productivity of the nomadic and semi nomadic livestock farming system and overestimation of the possibilities for increasing production by better management and by modernization.

No abstract

No abstract

No abstract

The article presents a critical evaluation of agroforestry systems as regards their potential to increase primary production in the Sahelian and Sudanian zones of West Africa. The suggestion that trees would always and everywhere be profitable for the region will be counterproductive, the basis for disappointments and a waste of money. One has to consider carefully which properties of woody species could serve which objective, where and under what circumstances.Primary production is limited by water availability in the north Sahelian zone only+ elsewhere in the region nutrient availability is critical. Woody species influence the water balance via rainfall interception+ the influence on evapotranspiration and the influence on water infiltration. The ultimate result for grasslands and crops depends upon local conditions: positive effects of windbreaks should be particularly attributed to protection against mechanical stress. Processes that influence nutrient availability under trees are those acting via redistribution, those reducing nutrient losses and those increasing soil fertility. Of the latter processes, serious limitations exist in the region concerned: nitrogen fixation is limited by phosphorus shortage mainly and deep rooting is very limited and so is possible uptake of minerals from deep soil layers.The positive influence from woody species on soil fertility and primary production varies with average annual rainfall and soil type; its importance increases more than proportionally with rainfall going south. This positive influence is basically linked to the redistribution of nutrients and water, the internal nutrient cycling and the related enlarged plant-litter-soil nutrient cycle. Taking advantage of its effects is difficult and risks further depletion of soil fertility. Moreover, since woody species generally compete with the herb layer+ it will be difficult to develop agroforestry in such a way that the positive influences are not overridden by negative ones. The potential to increase nutrient availability by agroforestry systems is limited and windbreaks are more beneficial under conditions which are rare in the region.More research is needed to determine under which conditions introduction of woody species may be beneficial. 42 R~rmeLe potentiel de l'agroforesterie pour augmenter la production primaire dans les zones sahOlienne et soudanienne de l'Afrique de l'Ouest Une 6valuation critique de l'agroforesterie est prrsentre, en ce qui concerne la possibilit6 d'augrnenter la production primaire dans les zones sahrlienne et soudanienne de l'Afrique de l'Ouest. La supposition que dans cette rrgion des arbres seraient toujours et partout avantageux, n'est pas productive, mais plut6t une cause de drceptions et un gaspillage de ressources. I1 faut se demander quelles proprirtrs des esprces ligneuses pourraient servir quels objectifs, off et sous quelles conditions. Seulement dans la zone nord-sah+lienne la production primaire est limit~e par la disponibilit6 en eau; aiUeurs c'est la disponibilit6 des 6lrme...