Terroirs comparison in terms of biomass flows and nitrogen balance : study case of Diohine and Barry Sine in the former groundnut basin
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- Master's theses (IPV) 
Physical, socio-political and economical changes impacted the former Senegalese groundnut basin what resulted in a strong natural resources use competition and therefore an agrarian transition that disconnects cropping and livestock farming sectors. Two terroirs were studied, one within a traditional model that conserved common fallows (Diohine), the other one that adopted livestock fattening practice (Barry Sine). Multi-scale nutrient balances based on surveys were sustainability indicators for the selected options and a participative workshop gathered their fertility management perceptions and dynamic per terroir and per gender. Plot scale nitrogen balances are both negative but higher for Diohine (-13 kgN.ha-1 for - 24kgN.ha-1 in Barry Sine) as well as nitrogen efficiency (116 for 4 à Barry Sine). On the other hand household and terroir scale nitrogen balances are positive and Barry Sine presents higher results (24kgN/ha-1 for 11 at household scale, 25kgN.ha-1 for 9kgN.ha-1 at terroir scale). Household nitrogen efficiency is higher in Diohine (1.11 for 0.92) but lower at terroir scale (0.12 for 0.64). Finally, soils fertility improvement tools described are different according to the terroir and genders with preferences per agricultural specialisation. Improvements are mainly based on existing practices intensification and on external funds but innovations and internal funding are considered.
Knowing the on-going population growth, climatic change, environmental deterioration, market regionalisation (nay globalisation) processes and observing that national food security is still not guaranteed, agricultural intensification (both crop and livestock) will be investigated for the former Senegalese groundnut basin. In soils impoverishment and yield stagnancy context, noting that extensive bovine herds progressive disappearance in the groundnut basin moved deeply soils fertility management system, it is relevant to wonder how the different agricultural strategies adopted by Barry Sine and Diohine villages can impact terroir’s environmental sustainability. We will question nowadays the interest of i) maintaining traditional system remainder adapted to new environmental constraints (Diohine case) ii) or favouring new fertility management rise structured around bovine fattening (Barry Sine case). These divergent managements impact biomass and nutrient flows differently according to the analysis scale adopted: plot, household or terroir scales. Nutrient and biomass flows analysis informs each scale functioning while nutrient balance is a largely admitted environmental sustainability indicator (Roy et al. 2005). In other words, we will focus on system opening multi- scale effects on nutrient balance and especially for the terroir scale adopting a systemic approach. To be able to plan agricultural future of the former groundnut basin, it is primordial to consider actor’s terroir perception in terms of soils fertility evolution and to grasp the fertility management practices evolution dynamics in order to increase production. In that purpose, a multiple perspective analysis that distinguishes both terroirs (Barry Sine and Diohine) and genders 22 (men and women) will be necessary to take into account the different social status distinction, their role within the household and their position into agricultural activities.