Limited food availability

While food security is a major worldwide issue, it is a much more serious problem in Low-Income (LI) and Lower Middle-Income (LMI) countries. Currently, sub-Saharan Africa is the sub-continent with the highest proportion of undernourished people, the largest gap between current and potential yields, and between cereal consumption and production. Looking to the future, population growth and climate change may worsen the situation, particularly in Africa. African countries are still facing rapid population growth with uncertain prospects about the ability of their agriculture to meet growing food demand. In addition, without sufficient adaptation measures, climate change will negatively impact food production in most African regions

Resource over-exploitation and running out

Food systems around the world are highly dependent on both renewable and nonrenewable resources. Drivers such as population growth, urbanisation and climate change put a lot of pressure on resources that have become core issues for the future of food systems. Cropland availability is limited in most parts of the world, adding pressure for cropping intensification. Fossil energy and phosphorus shortages are expected to occur within a few decades, with particular impact in Low-Income (LI) countries where farmers are more vulnerable to volatile prices. The availability of very unevenly distributed freshwater resources shows a similar picture, with an increasing number of regions reaching alarming levels of water scarcity. Some world fish stocks have been overexploited and are now depleted. But the situation is not without hope. While we need to intensify food systems to meet the challenge of a growing population, new ways to produce with less impact on the environment and more resilience to climate change need to be widely adopted

Conception and engineering of cropping systems: how to integrate ecological approaches?

The science of agroecology, which is defined as the application of ecological concepts and principles to the design and management of sustainable agroecosystems has known these last years a tremendous renewal of interest among the community of agricultural scientists but also amongst policy makers. This is mainly due to the important ecological disservices and often failure to ensure food security provided by intensive modern agriculture and associated techniques based on the combined use of agrochemicals and high-yielding varieties in monocropped systems. The main principle of agroecology consists in assembling and increasing functional biodiversity in agroecosystems to enhance synergisms in order to provide various categories of ecological services such as the activation of soil biology, the recycling of nutrients, and the enhancement of beneficial arthropods and antagonists. Functional diversity may be enhanced through different practices and strategies which include crop rotations, cover crops, intercrop ping, crop/livestock mixtures, agroforestry mixtures, etc. New strategies incorporating ecological knowledge gained from the observation of natural ecosystems and or traditional agroecosystems may be a credible alternative to design such innovative systems. Designing such novel agricultural systems calls for in-depth knowledge of biological regulations in ecosystems, but also for the integration of traditional agricultural knowledge held by local farmers. Integration of these two aspects is one of the challenges that agricultural science has to deal with today. In addition, although practices are ap plied at the plot and / or farm scale by farmers, their efficiency and associated services are expressed mainly at the landscape scale. This paper reviews the main initiatives that lie behind these trends, analyzes the basic concepts underlying the design of such systems, and suggests new frameworks for action that include Nature observation, experimental and model-based designs and participatory approaches. (Texte intégral

Pour un continuum de l'agronomie au développement local

Au sommaire - L'agronomie : délimitation du champ scientifique, définition, interface avec les sciences humaines pour contribuer au développement local. Les enjeux et les concepts scientifiques. La validité de ces concepts pour les agricultures tropicales. Trois domaines scientifiques complémentaires : l'évolution des états du milieu au sein des écosystèmes cultivés; le fonctionnement des peuplements végétaux au sein des écosystèmes cultivés; la gestion des écosystèmes cultivés. Les méthodes et les outil

A food web based model for cropping system simulation : A first application to banana systems

Recent experiments an agricultural ecosystems have shown that resilience is the key factor of their sustainability. Here, we suggest that to assess the resilience of agricultural systems with models, it is necessary to consider the complete food web of the simulated systems and not only the productive crops, soil chemistry and eventually crop parasites as usual plant focused cropping systems models do. We attend to reconcile ecological and agronomical approaches through the concept of food web based cropping system model. Food web models are typically used to understand population dynamics and semmunities structures in many ecosystems e.g. aquatic or soil ecosystems. We specifically present a model aimed at simulating a cultivated field as a foil to the traditional cropping system models. We argue that this concept has different implication for understanding field resilience including the interaction between parasite and non parasite communities, physical and chemical soil characteristics. To this end, we offer contrasting prediction of soil characteristics, crop productivity and parasite populations using the SIMBA model with and without taking into account soil food web structure and interactions. Primary production and most damaging parasites of banana (e.g. plant-parasitic nematodes) are simulated by the standard modules of the SIMRA model. Other trophic levels (i.e. decomposers, primary consumers omnivores. predators) are accounted within a simple food web module based on bottunwup and top-down control of populations. Incorporating the variation in food web structure into cropping systems models parameterized for banana systems allows more precise and more realistic simulations of production and parasite dynamics. These results provide evidence that incorporating food web structure can he useful in the search for more accurate prediction of cropping system resilience and for designing more sustainable cropping systems.. The conceptual framework that we present here is generic and aim to tackle functional biodiversity in other contexts. As a perspective, we discuss the possibility to use measures of natural isotopic abundance to parameterize such a tool. (Texte intégral

Analyse de la variabilité des rendements chez l'ananas (Ananas comosus L. Merr.). II. Relations entre séquence climatique et fonctionnement du peuplement végétal dans les conditions de Côte d'Ivoire

Dans une étude portant sur 120 parcelles d'ananas plantées mensuellement en Côte d'Ivoire, les corrélations entre des indicateurs de croissance, le rendement et certains paramètres caractérisant la qualité du fruit ont été étudiées. Les différents schémas de fonctionnement observés ont pu être reliés à certains paramètres climatiques et plus particulièrement à l'énergie solaire reçue par la culture et à l'intensité du déficit hydrique. Le rayonnement et le déficit hydrique durant la phase végétative déterminent la biomasse présente au moment de l'induction florale, fixant ainsi un potentiel de rendement. Le rayonnement durant la fin de la phase de fructification jouerait ensuite un rôle déterminant dans l'orientation des assimilats dans la plante et sur le niveau de remplissage du fruit. Les résultats établis fournissent des éléments pour comprendre la variabilité des rendements obtenus en Côte d'Ivoire en culture d'ananas et permettent de mettre en évidence l'existence de période privilégiées de calage du cycle de la culture dans l'année. (Résumé d'auteur