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Une démarche agronomique pour accompagner le changement technique. Cas de l'emploi du traitement herbicide dans les systèmes de culture à sorgho repiqué au Nord-Cameroun

Abstract : The spread of dry season sorghum, which concerns the whole lake Chad basin, is now attaining remarkable proportions in the farming systems of far-northern Cameroon. The crop is grown in vast areas of clayey soil, partially flooded, that are difficult to till during rainy season, and achieves its cycle with the use of soil water reserve. Herbicide treatment, introduced recently, is more and more used because of its agronomic advantages to clean the fields faster and to control perennial weeds, but also economic, by slightly reducing the costs in comparison to farm labourers employment. An adaptive research has been carried out to reach the most moderate use of herbicide. Two levels were considered for this agronomic approach : one concerns the understanding of farmers problems through analysis and formalisation of their decision rules to monitor the crop ; the other deals with the assessment of new decision rules concerning the use of herbicide, on sorghum yield and weeds populations. The combination of these both levels of agronomic knowledges allows to support farmers on the most proper way to integrate a new technology in their cropping systems, by taking advantage of their know-how. This approach relies on farmers interview at the farm level and cropping system experiments at the field level, in two study sites. Analysis shows a strong soil heterogeneity between and inside plots, on which farmers rely to achieve successive cultivation techniques and to realise transplantation in optimal soil moisture conditions in spite of the slowness of manual work and the short period to set the crop. Soil water reserve appears to be the principal limiting factor for transplanted sorghum. Weeds competition has an impact on crop production especially in the most humid soils, often flooded during years of high rainfall. In those situations, herbicide treatment offers a yield increase of, at least, 20 % and more in areas infested by perennial weeds. In situations dominated by annual Gramineae, herbicide doesn't lead to an improvement of sorghum production and should be used only as a punctual solution, especially during years with low rainfall to avoid farmers to delay implantation of their fields. These results allow to specify decision rules concerning the use of herbicide for an integrated weeds management : localisation of treatments and adjustment of dose according to the heterogeneity of cultivated environments; succession of herbicide treatment and manual cleaning mode, according to the climatic scenario and the weeds population. This research, lead in a development program, closely contributed to reinforce advisory services at a regional scale, in order to limit negative impacts of this innovation on natural environment and local employment
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Submitted on : Friday, February 3, 2006 - 8:00:00 AM
Last modification on : Monday, October 19, 2020 - 11:12:38 AM
Long-term archiving on: : Friday, September 10, 2010 - 3:28:03 PM


  • HAL Id : pastel-00001183, version 1


Bertrand Mathieu. Une démarche agronomique pour accompagner le changement technique. Cas de l'emploi du traitement herbicide dans les systèmes de culture à sorgho repiqué au Nord-Cameroun. Agronomie. INAPG (AgroParisTech), 2005. Français. ⟨NNT : 2005INAP0002⟩. ⟨pastel-00001183⟩



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