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Rennes, France

Ridier A.,Agrocampus Ouest
Canadian Journal of Agricultural Economics | Year: 2012

In this paper, we propose an analysis and modeling of farmers' decision to convert a part of their annual crops area into woody crops: short rotation coppices (SRCs). Different criteria-technical, economic, and financial-are highlighted in the farmers' decision to adopt this production. A farm-level model is proposed and incorporates these decision criteria. The objective is to test several incentive scenarios to encourage risk-averse cereal farmers to plant trees. A multiperiod model of investment is built and tests possible adoption by farmers based on financial and structural parameters and according to the outlook of agricultural markets. The simulations show that if the cash crop prices fluctuate in the future and if farmers are risk averse the strategy of on-farm diversification toward woody crops under contractual arrangements could be relevant for farmers to mitigate the risks in the long run. Cet article présente une analyse et une modélisation de la décision d'un agriculteur céréalier qui souhaite convertir une partie de sa surface en grande culture en Taillis à Courte Rotation (TCR). Un modèle multi-périodique d'investissement est construit et incorpore différents critères techniques, économiques et financiers qui entrent dans la décision d'adopter ces nouvelles cultures pérennes. Le modèle permet de tester le rôle de différents types de soutiens, proposés aujourd'hui dans le cadre de la Politique Agricole Commune européenne, permettant d'encourager les agriculteurs averses au risque à planter des arbres. Les simulations montrent que si les prix des grandes cultures annuelles fluctuent à l'avenir, si la plantation d'arbres est soutenue et si les agriculteurs sont averses au risque, la stratégie de se diversifier vers la plantation d'arbres à croissance rapide, sous contrat, peut permettre d'atténuer le risque à long terme. © 2012 Canadian Agricultural Economics Society. Source


Gaucheron F.,Agrocampus Ouest
Journal of the American College of Nutrition | Year: 2011

Milk and dairy products contain micronutrients such as minerals and vitamins, which contribute to multiple and different vital functions in the organism. The mineral fraction is composed of macroelements (Ca, Mg, Na, K, P, and Cl) and oligoelements (Fe, Cu, Zn, and Se). From a physicochemical point of view, the chemical forms, the associations with other ions or organic molecules, and the location of macroelements such as Ca, Mg, Na, K, P, and Cl in milk are relatively well described and understood. Thus, it is admitted that these macroelements are differently distributed into aqueous and micellar phases of milk, depending on their nature. K, Na, and Cl ions are essentially in the aqueous phase, whereas Ca, P, and Mg are partly bound to the casein micelles. About one third of the Ca, half of the P, and two thirds of the Mg are located in the aqueous phase of milk. Dairy products are more or less rich in these different minerals. In cheeses, mineral content depends mainly on their processing. The Ca content is strongly related to the acidification step. Moreover, if acidification is associated with the draining step, the Ca content in the cheese will be reduced. Thus, the Ca content varies in the following increasing order: milks/fermented milks/fresh cheeses, soft cheeses, semi-hard cheeses, hard cheeses. The chemical forms and associations are less described than those present in milk. Concerning Ca, the formation of insoluble calcium phosphate, carbonate, and lactate is reported in some ripened cheeses. The NaCl content in cheeses depends on the salting of the curd. From a nutritional point of view, it is largely admitted that milk and dairy products are important sources of Ca, Mg, Zn, and Se. The vitamin fraction of milk and dairy products is composed of lipophilic (A, D, E, and K) and hydrophilic (B1, B2, B3, B5, B6, B8, B9, B12, and C) vitamins. Because of their hydrophobic properties, the lipophilic vitamins are mainly in the milk fat fraction (cream, butter). The hydrophilic vitamins are in the aqueous phase of milk. For one part of these vitamins, the concentrations described in the literature are not always homogenous and sometimes not in accordance between them; these discrepancies are due to the difficulty of the sample preparation and the use of appropriate methods for their quantification. However, there is no doubt of the significant contribution of milk and dairy products to the intake of vitamins. Milk and dairy are considered essential sources for vitamins. Source


Le Pape O.,Agrocampus Ouest | Bonhommeau S.,French Research Institute for Exploitation of the Sea
Fish and Fisheries | Year: 2015

Coastal zones are productive areas that serve as nursery grounds for a large number of marine species. However, the processes involved in survival success during the juvenile phase are not well-known. Some authors suggest that the availability of prey is important to support the production of pre-recruit fish whose fitness is enhanced through optimal feeding conditions. Accordingly, recruitment is limited by the carrying capacity of the nursery habitat. In contrast, other authors state that the carrying capacity of the nursery grounds is not fully exploited, suggesting that there is no effect of food limitation. This study combines an overview of the literature, focused on flatfish that are especially dependent on coastal and estuarine nursery grounds, an extension to other marine fishes and a modelling approach on growth and survival of juvenile fish to explore the controversy of food limitation in their nursery grounds. We demonstrate that the relative lack of growth limitation observed for young marine fishes at the individual scale is related to an observational bias: fish have been affected by size-selective mortality linked to food limitation, but only surviving individuals are observed. As the population is skewed towards the faster-growing juveniles, the growth of survivors remains close to optimal, even when food resources are limited. Food limitation is of major influence in determining the carrying capacity of the nursery habitat. To sustain marine fish populations and related fisheries, management action is needed to protect coastal and estuarine areas and maintain or restore nursery productivity. © 2013 John Wiley & Sons Ltd. Source


Gohin A.,Agrocampus Ouest
Renewable and Sustainable Energy Reviews | Year: 2016

The estimations of land use changes and greenhouse gas emissions induced by biofuels remain highly controversial. After some first estimates in 2009, the California Air Resource Board releases new estimates in 2014. This paper explains two striking new results. First, the absolute reduction in the estimate of average US soya biodiesel is much greater than the reduction in the estimate of average US corn ethanol (by respectively 33 and 10 g CO2 eq/MJ). According to the new estimates, these two biofuels now induce more similar greenhouse gas emissions. Second, the newly reported EU and US canola biodiesel estimates are very different (respectively greater than 35 and 10 g CO2 eq/MJ). Using the public and transparent methodologies developed by the California Air Resource Board, we find that these two striking results are mostly explained by some weak initial economic data. In both cases, the undervaluation of the initial oilmeal productions generates upward bias in the land use changes and carbon emission estimates by reducing the co-product effects. We find that the new closer estimates reported for the US soya biodiesel and corn ethanol are explained by an appropriate revision of the world production of oilmeal and the inclusion of oilmeal trade flows. We also find that the reported significant difference between the EU and US canola biodiesel estimates nearly disappears when the initial data on European land values, oilmeal production and trade values are improved. We then emphasize that any economic analysis is only as valuable as the quality of the supporting data allows. The current focus in academic and policy circles on unobserved elasticity values to assess biofuel impacts is not sufficient. © 2015 Elsevier Ltd. All rights reserved. Source


Michel J.-C.,Agrocampus Ouest
Vadose Zone Journal | Year: 2015

Hydrophobicity of organic matter is the primary factor affecting soil physical properties such as soil structural stability after drying. In horticultural production, the measurement of wettability is even more relevant due to the large use and high content of organic materials in growing media and to the large and rapid variations in water content in the media (due to the limited volumes of pots or containers), both of which can quickly create hydrophobic conditions. This review discusses the methods used for measuring the wettability of growing media, the evolution of wettability vs. water content, ways for limiting hydrophobicity, and finally the relationships between growing media wettability and physical properties. In addition to the indirect estimation of hydrophobicity based on physical properties such as water holding capacity, contact angles obtained from capillary rise and hydration efficiency tests are the most common methods describing the changes from hydrophilicity to hydrophobicity of organic growing media in relation to water content. Wetting agents and clay have been shown to reduce the water repellency of growing media under the driest conditions. A general trend of increasing water repellency during desiccation from highly decomposed peat > bark > weakly decomposed peat > wood products > coco fiber has been documented. As for water retention, hysteresis phenomena in contact angles have been shown during drying–wetting cycles. The influence of hydrophobicity on water retention characteristics has also been modeled, providing evidence that hydrophobicity is a function of the growing medium pore size domain. The reciprocal effects of physical and biological roles of roots on the wettability and physical properties of growing media should be investigated in future research. © Soil Science Society of America. Source

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