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Impact de pratiques agricoles conventionnelles et innovantes sur la fertilité des sols et les acteurs microbiens impliqués dans la zone de savanes humides de Côte d’Ivoire

Abstract : In West Africa, humid savanna soils are characterized by extremely low concentrations of organic matter, mineral nitrogen, phosphorus and basic cations, which limit primary production. We analyzed how particular changes in land-uses can influence the functioning and fertility of soils, to support the production of agroecosystems in this savanna zone. We compared six land-use types at 9 experimental plots across a landscape: traditional slash-and-burn; conventional chemical fertilization; and innovative use of mulching (tested with or without inserting legumes in the crop rotation). Bare soil was also considered as a reference situation. Soil was sampled on the 54 sub-plots, before and 3 times after treatment inception. We surveyed seven soil enzyme activities (denitrification, nitrification, β glucosidase, N-acetyl-β-D-glucosaminidase, acid and alkaline phosphatase, dehydrogenase), key soil variables (moisture, organic C, mineral and total N, pH, and available P) and the abundances and diversity of microbial communities involved in the N cycle (bacterial and archaeal ammonia oxidizers; Nitrobacter; Nitrospira; and nirS-, nirK- and nosZ-like denitrifiers). Our results showed that (i) C. org, K, Mg and soil enzymes activities decreased with soil depth, reflecting a low rate of nutrient accumulation in soil depth. In contrast, fallow periods (0 to 10 years) did not significantly affect the majority of soil properties, excepted soil Ntot and K, which were high in old fallows. In addition, C. org decreased as a function of the fallow period, but Mg follow-up an inverse trend; (ii) the land use type strongly affects most soil enzymatic activities and the microbial communities involved in nutrient cycling; (iii) innovative mulching practices have a positive impact on soil characteristics and microbial communities, thereby maintaining the maintenance of soil fertility and the sustainability of agricultural production in the long term. According to our results, the practice of mulching, possibly with the insertion of legumes, could be less expensive and more appropriate to progressively and sustainably increase nitrogen availability in these agro-ecosystems
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Submitted on : Monday, October 15, 2018 - 7:21:06 PM
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Embi Féline Laurenza Assemien. Impact de pratiques agricoles conventionnelles et innovantes sur la fertilité des sols et les acteurs microbiens impliqués dans la zone de savanes humides de Côte d’Ivoire. Biochimie [q-bio.BM]. Université de Lyon, 2018. Français. ⟨NNT : 2018LYSE1103⟩. ⟨tel-01896147⟩

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