Strategies and economics of farming systems with coffee in the Atlantic Rainforest Biome

In the Zona da Mata of Minas Gerais State, Brazil, family farmers are adjusting to agroecological principles to reconcile sustainable agriculture, livelihood improvements and biodiversity conservation. Starting in 1993, experimentation with coffee agroforestry was gradually initiated on an increasing number of farms (37 in total), resulting in the simultaneous management of sun coffee (SC) and agroforestry coffee (AF) plots. We aimed (1) to identify factors that determine the farmers’ selection of trees used in AF; (2) to describe the agroecological farms in transition; and (3) to perform an economic comparison between AF and SC. These objectives were addressed by combining data from botanical surveys in 1993/1994 and 2007, by interviews with farmers and by detailed data on the production value and costs of labour and material inputs. The results showed considerable diversity in farming strategies and management among the farmers. Early adopters of AF had diversified towards production of different marketable products. The use of native trees in AF for this purpose, and for restoration of soil fertility (e.g., leguminous trees), had increased since the start of the experiments, while exotic tree species were eliminated. Over a period of 12 years AF was more profitable than SC due to the production of a diversity of agricultural goods, despite somewhat higher establishment costs. Other ecosystem services delivered by AF, such as biodiversity and cultural services are currently not valorized. Payment schemes for environmental services could further improve the economic benefits of AF for family farmers and alleviate establishment and learning cost

An empirical model for early resistance changes due to electromigration

A new heuristic description for electromigration-induced early resistance changes is given. The basis is formed by two coupled partial differential equations, one for vacancies, and one for imperfections. These equations are solved numerically for a grain boundary bamboo structure. It is shown that this model is capable of simulating the typical effects as observed in early resistance change measurements. These early resistance changes are due to the redistributions of the vacancies and the generation of imperfections. Simulations are performed that closely match the measured resistance change curves

The impact of long-term elevated CO2 on C and N retention in stable SOM pools

Elevated atmospheric CO2 frequently increases plant production and concomitant soil C inputs, which may cause additional soil C sequestration. However, whether the increase in plant production and additional soil C sequestration under elevated CO2 can be sustained in the long-term is unclear. One approach to study C-N interactions under elevated CO2 is provided by a theoretical framework that centers on the concept of progressive nitrogen limitation (PNL). The PNL concept hinges on the idea that N becomes less available with time under elevated CO2. One possible mechanism underlying this reduction in N availability is that N is retained in long-lived soil organic matter (SOM), thereby limiting plant production and the potential for soil C sequestration. The long-term nature of the PNL concept necessitates the testing of mechanisms in field experiments exposed to elevated CO2 over long periods of time. The impact of elevated CO2 and N-15 fertilization on L. perenne and T. repens monocultures has been studied in the Swiss FACE experiment for ten consecutive years. We applied a biological fractionation technique using long-term incubations with repetitive leaching to determine how elevated CO2 affects the accumulation of N and C into more stable SOM pools. Elevated CO2 significantly stimulated retention of fertilizer-N in the stable pools of the soils covered with L. perenne receiving low and high N fertilization rates by 18 and 22%, respectively, and by 45% in the soils covered by T. repens receiving the low N fertilization rate. However, elevated CO2 did not significantly increase stable soil C formation. The increase in N retention under elevated CO2 provides direct evidence that elevated CO2 increases stable N formation as proposed by the PNL concept. In the Swiss FACE experiment, however, plant production increased under elevated CO2, indicating that the additional N supply through fertilization prohibited PNL for plant production at this site. Therefore, it remains unresolved why elevated CO2 did not increase labile and stable C accumulation in these systems

Environnement humain de l'érosion

Dans le cadre des évaluations économiques des mesures de conservation des eaux et du sol, on propose d'utiliser des méthodes et modèles existants pour déterminer les effets de ces mesures sur l'érosion et sur les bilans d'eau et d'éléments nutritifs et ensuite les effets des changements sur les rendements. Dans ce texte on présente des "feuilles de calcul", y incluant ces bilans et effets, afin de calculer les bénéfices des mesures de CES. Un exemple concerne l'évaluation économique des cordons pierreux au Burkina Faso. (Résumé d'auteur

Rethinking erosion on Java: a reaction

In a recent article (Diemont et al., 1991) about erosion on Java, it has been postulated that low inputs, not surface erosion, is the main cause of low productivity of upland food crops on this island. In this article it is argued that this hypothesis is too simple. An analysis of empirical field data about the effect of erosion on crop productivity indicates that the effects of erosion and agronomic inputs are confounded. Erosion causes farmers to apply low inputs because only limited returns can be expected on eroded lands. The relations between erosion and crop productivity are site specific; the extent and quality of conservation measures and intensity of agronomic inputs varies per soil type

Multivariate Typology of Farm Households Based on Socio-Economic Characteristics Explaining Adoption of New Technology in Rwanda

The challenge for agricultural policymakers and planners, particularly in the context of Rwanda with high population density and consequently food insecurity, is how to enable farmers to adopt new technology. It is known that adoption of new technology may vary among farm households because of socio-economic characteristics. This paper intends to typify farm households in Rwanda based on the exploration of factors explaining adoption of new technology. Ultimately, typical farms obtained from the typology will be used, later as basis to develop representative mathematical programming models. Multivariate statistical techniques offer the means of creating such typologies, particularly when an in-depth database is available. This multivariate analysis approach, combining principal component analysis (PCA) and cluster analysis (CA), has allowed us to identify clearly five typical farm households and their socio-economic characteristics explaining adoption of new technology.. Multivariate statistical techniques, such as PCA and CA, are great tools to envisage building mathematical programming models on the basis of typical farm households.Agricultural and Food Policy, Community/Rural/Urban Development, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, Land Economics/Use, Marketing, Production Economics, Research and Development/Tech Change/Emerging Technologies,