Multi-level analysis of nutrient cycling within agro-sylvo-pastoral landscapes in West Africa using an agent-based model

Abstract

Livestock-driven nutrient flows are the main sources of soil and crop fertilization in West African agro-sylvo-pastoral landscapes. They result from nutrient recycling between farm activities and the spatial transfer of nutrients within the landscape. "Extensive" systems, based on livestock mobility are tending to be replaced by more "intensive" systems based on in-barn livestock fattening. We built an agent-based model to compare these systems in terms of nitrogen cycling at land plot, herd, household and village levels. Model evaluation, based on field-data from two real contrasted villages, showed that the model satisfactorily reproduces the differences between an "extensive" and an "intensive" system with key parameters such as variability among households and soil fertility gradients. Simulations highlighted bottlenecks along the nitrogen (N) cycle like accumulation of N in manure heaps and housing areas, reducing N recycling efficiency, especially in "intensive" systems. The model can be further used to explore improved agro-sylvo-pastoral landscapes.

Élevages au pâturage et développement durable des territoires méditerranéens et tropicaux

“…La thèse de Daniel Pinillos a produit un premier jeu de données permettant de quantifier des services écosystémiques sur la commune de Paragominas et de réaliser des simulations en fonction de réglementations locales (Pinillos, 2021a) Ces résultats illustrent que l'azote est un facteur limitant majeur de la productivité des agroécosystèmes en Afrique de l'Ouest, et qu'accroître les entrées d'azote dans les villages sous forme d'aliments pour les animaux permet à la fois d'accroître la production de viande, la production de céréales et la fertilité des sols. En effet, ces ressources alimentaires extérieures au territoire permettent de maintenir des chargements animaux élevés, intensifier les processus écologiques (dont la concentration de la fertilité par l'intermédiaire des animaux) et accroître les efficiences techniques et environnementales des SASP (Grillot et al, 2018a). La dépendance aux ressources extérieures pose question en ce qui concerne la durabilité ; elle reste acceptable tant qu'elle se limite à une valorisation des coproduits de l'agro-industrie nationale par les animaux, puisqu'elle n'entre pas en compétition avec l'alimentation humaine.…”

Ecological and financial strategies provide complementary benefits for smallholder climate resilience: insights from a simulation model

“…This representation generally follows Liebig's law of the minimum, which assumes that yields are influenced solely by the most constraining of these factors and plateau when each factor is above some threshold (Tittonell andGiller 2013, Ferreira et al 2017) (i.e., the crop can be water-or nutrient-limited). Similar representations are used in other more complicated process-based models of crop yield (e.g., CENTURY (Metherell et al 1993), STICS (Brisson et al 2003)) and in other simulation models (Grillot et al 2018).…”

Sustainable Agroforestry Landscape Management: Changing the Game

“…Water, nutrients, biomass, labor, information and money move in the landscape, while many studies focused on biomass production at farm scale only considering single households [116][117][118], without their interactions. Biomass management through farmers' decisions on biomass allocation [119], include use of crop residues as livestock feed [120], indirectly influencing manure availability for crop production. At village scale, biomass production is determined by farmers' organization, the spatial and temporal interactions amongst farmers, and between farmers and their biophysical environment (soil fertility), as farmers can organize themselves in "labor-groups" to till each other's fields and thus be able to cultivate more land.…”