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Assessing autonomy and nutrient use efficiency of dairy sheep farming systems in Roquefort (France) through systemic nitrogen flow analysis
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Edité par CCSD -
CONTEXT: Because of climate change and the forecast trends, the sustainability and resilience of the intensified dairy sheep farming systems are threatened. To adapt, there is consensus about the interest in redesigning key farm operations (e.g. feeding system) by relying more on agroecological principles.
We aimed to characterize and assess a dairy sheep farming system in the main basin for this sector in France (Roquefort), to determine to what extent the quest for autonomy is at the expense of nutrient use efficiency, leading to identifying opportunities for improving sustainability METHODS: An in-depth analysis of nutrient flow was carried out by studying the nitrogen (N) flows with a systemic approach and using the ENA (ecological network analysis) methodology. Data were collected from the INRAE La Fage experimental farm, in Roquefort, France's main dairy sheep production region, during the period 2015-2019. Structural and agroecological indicators of the system's functioning were calculated. RESULTS AND CONCLUSIONS: Farm feed (supplement) and forage autonomy were at 78.0 and 90.6 %, respectively. On average, the system was up to 69 % self-sufficient, indicating the existence of farming practices enhancing closing N cycles. The farming system's N efficiency was low (12.6 %) compared to the N efficiency of the livestock (48.7 %) and crops (65.0 %) compartments considered separately; hence the importance of the holistic approach and the contribution of the various components of the livestock farming system for a better understanding of the system's performance-building process. The system's annual N flow network productivity was low (22.6 kg N ha-1). Overall, the system was strongly influenced by natural N inputs, especially rainfall and symbiotic fixation (49 % of total inputs). Leaching caused most of the N losses within the system (67.0 %) and represented 87.0 % of the total arable land N losses. Overall, 80.0 % of the effluents produced in the sheepfold were recycled through manure spreading in the cropping system plots to produce feed (i.e., hay, silage, and barley). Around half of the total system N flows were provided by internal nutrient flows between the crop and livestock sub-systems (45.0 %) while 36.0 % came from inputs. Results revealed high autonomy levels (78.0 % for feed and 90.6 % for forage), and opportunities to increase the overall farming system's performance mainly through reducing N losses and enhancing the nutrient use efficiency.
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