Effets des modes de gestion des terres en zone sahélienne sur les termes et l'évolution de leur bilan organique et biologique : consequences pour une production céréalière soutenue :cas du Sénégal

Abstract : In the sahelian zone, sail organic matter (SOM) and microbial biomass (MBc) are two essential components of soil fertility, SOM because of it's role in sail physical properties and stock of nutrients, and MBc as the key of most of the biological processes involved in SOM evolution. Our objective is (1) to evaluate the effects of organic inputs on sail fertility, using chemical and biological variables as well as yield components and (2) to determine the relationships between these variables so as to define types of soil behaviour that could explain the large variability of the response to manure in field conditions. We worked on medium-term and annual experiments as weil as a multilocal experiment in field conditions. Our variables are soil physico-chemical caracteristics, MBc, nitrification determined in situ (Nitn1) and in controlled conditions (Nitpot) as the biological variables, and plant prùductivity as an integrative variable. Our results confirm the fast degradation of SOM the first year of cultivation after 15 years of herbaceous fallow (-40% C the first year). This study also presents new results : (1) it validate, in field conditions, the increase of MBc during the cultivation period observed by other authors in agronomical station and precises the relationships between soil biological component (MBc and Nitm) and chemical ones (CEC, SOM) ; (3) it shows that the variability of the soil and plant reponse to manure is a function of it's composition and of the ecological zone; this variability is used to define types of sail behaviour; (4) it shows that residual effects of manure is still sensible, even after two years, on yield and MBc. This work also led to methodological studies. Controlled conditions are necessary for a better knowledge of biological mecanisms.
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Paula Fernandes. Effets des modes de gestion des terres en zone sahélienne sur les termes et l'évolution de leur bilan organique et biologique : consequences pour une production céréalière soutenue :cas du Sénégal. Sciences agricoles. Institut National Polytechnique de Lorraine, 1999. Français. ⟨NNT : 1999INPL110N⟩. ⟨tel-01749907⟩

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