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Abstract The objective of this work was to define experimental blocks for sugarcane experiments using geostatistical techniques, principal component analysis, and clustering techniques applied to soil properties. For this, data of soil chemical properties from a sugarcane experiment were used. Geostatistical techniques were applied to identify the spatial variability of these properties and to estimate the values for non-sampled locations through kriging. The principal components analysis was used for dimensional reduction, and, with the new variables obtained, the cluster analysis was performed using the k-means method to determine the experimental blocks with two to five replicates. Of the 12 analyzed variables, 10 showed spatial dependence. The principal component analysis allowed reducing the dimensionality of the data to two variables, which explained 82.27% of total variance. The obtained blocks presented irregular polygonal shapes, with different formats and sizes, and some of them showed discontinuities. The proposed methodology has the potential to identify more uniform areas in terms of soil chemical properties to allocate experimental blocks for sugarcane.

Testing emerging technologies, such as autonomous vehicles, predictive crime analytics, and smart city interventions under real-world conditions is an important strategy for robust and responsible technology development. However, the moral responsibilities of researchers towards the public when conducting such real-world experiments are often left unaddressed and unregulated. This article argues that there are problematic inconsistencies in research ethics demands and protections across different categories of research and development with emerging digital technologies. This differential treatment is problematic since there are no meaningful differences to justify it, and it creates the possibility of regulatory evasion at the cost of populations’ due protection. Hence, I argue that this differential treatment should be amended by harmonizing research ethics demands. In doing so, this paper contributes to several ongoing scholarly debates on the limits of current research ethics guidelines and protocols in the face of novel technologies and research formats.

Adoption of conservation farming practices such as zero tillage when planting field research plots is essential to the replication of on-farm practices. The problem is that most drill options fail to meet expectations as they are not built to the scale required, compromise the need for uniformity of plant emergence within plot areas, lack portability, or have been designed and equipped in a manner that is not relevant to farm-scale seeder technologies and practices. Agronomists and Technicians at Agriculture and Agri-Food Canada engaged with engineering expertise to design and build two prototype drills that are now in full operation. [ABSTRACT FROM AUTHOR]

Invasive alien species are a major threat to seabird species, and the number of impacted species is still increasing. A recent study revealed for the first time that feral cats predated a large albatross species and that without cat control, some albatross populations would markedly decline. We examined this new predator–prey system by individually monitoring known‐age wandering albatross chicks with camera traps in a colony experimentally divided into zones with and without cat control. Our design allowed us to investigate how cat control influenced cat abundance and how this in turn influenced the probability for a chick to be predated by a cat. After cat controls, cat abundance was lower in controlled zones than in uncontrolled zones, while a survival analysis showed that the probability for a chick to die from cat predation depended on the zone but not on cat abundance. Our monitoring also provided a fine‐scale investigation of the various sources of chick mortality. In addition to cat predation (24% of mortality overall), our data documented predation by giant petrels, for the first time in Kerguelen, and revealed a strong and unexpected effect of nest flooding on chick mortality. Overall, our results underline the need for future studies investigating interindividual variability in cat diet and spatial ecology. [ABSTRACT FROM AUTHOR]

Abstract Invasive alien species are a major threat to seabird species, and the number of impacted species is still increasing. A recent study revealed for the first time that feral cats predated a large albatross species and that without cat control, some albatross populations would markedly decline. We examined this new predator–prey system by individually monitoring known‐age wandering albatross chicks with camera traps in a colony experimentally divided into zones with and without cat control. Our design allowed us to investigate how cat control influenced cat abundance and how this in turn influenced the probability for a chick to be predated by a cat. After cat controls, cat abundance was lower in controlled zones than in uncontrolled zones, while a survival analysis showed that the probability for a chick to die from cat predation depended on the zone but not on cat abundance. Our monitoring also provided a fine‐scale investigation of the various sources of chick mortality. In addition to cat predation (24% of mortality overall), our data documented predation by giant petrels, for the first time in Kerguelen, and revealed a strong and unexpected effect of nest flooding on chick mortality. Overall, our results underline the need for future studies investigating interindividual variability in cat diet and spatial ecology.

Socially assistive robotics (SAR) is getting a lot of attention for its potential in assisting elderly users. However, for robotic assistive applications to be effective, they need to satisfy the particular needs of each user and be well perceived. For this purpose, a personalization based on user's characteristics such as personality and cognitive profile, and their dynamic changes is a crucial factor. Moreover, most of the existing solutions rely on the availability of specific technological infrastructures, generally requiring high economic investment, and that cannot be easily placed in different environments. Personalization and adaptation of assistive robotics applications to different user's characteristics and needs, and even to different technological environments, are still not fully addressed in real environments. In the present work, the results of the UPA4SAR project are presented. The project aimed at providing a social robotic system to deliver assistive tasks for home care of patients with mild cognitive impairment in a personalized and adaptive way. We introduce the general architecture of the system and the developed robotic behaviors. Personalization and dynamic adaptation of assistive tasks are realized using a service-oriented approach by taking into account both user's characteristics and environmental dynamic conditions. Field experimentation of the project was carried out with 7 patients, using the robotic system autonomously running in their homes for a total of 118 days. Results showed a reliable functioning of the proposed robotic system, a generally positive reaction, and a good acceptability rate from patients. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate the content and uptake of macronutrients (P, Ca, Mg, K) in Solanum tuberosum tubers and the effect of care with biostimulants from a three-year field experiment conducted at the Agricultural Experimental Station in Zawady, Poland. The experiment was set up in a split-plot arrangement with three replications. The first factor was two varieties of edible potato (Oberon and Malaga), and the second factor was five treatments with herbicide and biostimulants: (I) control facility, (II) herbicide (chlomazone + metribuzin), (III) herbicide and biostimulant PlonoStart, (IV) herbicide and biostimulant Aminoplant, (V) herbicide and biostimulant Agro-Sorb Folium. Biostimulants and herbicide increased the concentration of P, Mg, Ca, and K compared to tubers harvested from the control facility. The Oberon variety had the highest macro-nutrient uptake capacity. The application of herbicide with biostimulants increased the uptake of the mentioned mineral nutrients compared to the control variant. Climatic conditions affected the content and uptake of selected elements. [ABSTRACT FROM AUTHOR]

Current structural models used for the flexural design of prestressed concrete sleepers assume that ballast bearing support is static and located within a fixed region. This assumption implies a linear relationship between wheel load and bending moment. However, field data gathered from instrumented sleepers shows that this trend is non-linear, and the difference in flexural behavior between model predictions and field-measured demand is significant. Using back-calculation techniques and the development of a sleeper support analysis tool, this paper investigates the load-dependency of sleeper support condition. It is hypothesized that a given support condition redistributes ballast reaction forces due to the mechanical interaction of ballast particles with the sleeper's deflected shape. It was found that redistribution of support conditions can reduce the expected flexural bending moment up to 45% when compared with moments calculated using traditional design guidelines. This effect (non-linearity) is greater as wheel loads increase. Results from revenue service field experimentation provided insight into the interaction between sleeper and ballast and serve as a foundation for the development of more complex analytical models. This will facilitate revisions to the future flexural design procedures for concrete sleepers, to ensure they are optimized for their expected service loading conditions. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate the content and uptake of macronutrients (P, Ca, Mg, K) in Solanum tuberosum tubers and the effect of care with biostimulants from a three-year field experiment conducted at the Agricultural Experimental Station in Zawady, Poland. The experiment was set up in a split-plot arrangement with three replications. The first factor was two varieties of edible potato (Oberon and Malaga), and the second factor was five treatments with herbicide and biostimulants: (I) control facility, (II) herbicide (chlomazone + metribuzin), (III) herbicide and biostimulant PlonoStart, (IV) herbicide and biostimulant Aminoplant, (V) herbicide and biostimulant Agro-Sorb Folium. Biostimulants and herbicide increased the concentration of P, Mg, Ca, and K compared to tubers harvested from the control facility. The Oberon variety had the highest macro-nutrient uptake capacity. The application of herbicide with biostimulants increased the uptake of the mentioned mineral nutrients compared to the control variant. Climatic conditions affected the content and uptake of selected elements.

"Means efficacy" complements self-efficacy. It refers to one's belief in the usefulness of external resources or tools that may be useful for performance. Research has confirmed the hypothesis that enhancing means efficacy boosts performance. Course efficacy is students' belief in the usefulness of a course. Two pilot studies and three field experiments tested the means efficacy-performance hypothesis casting university courses as the means. The manipulation check validated the experimental treatment in only one pilot and there was no evidence that the treatment contributed to performance. Explanations of these results and ideas for future research are suggested. [ABSTRACT FROM AUTHOR]

The citrus fruit grower has hardly adopted innovations, resulting in reduced income and profitability. This study aims to apply andragogic training and extension techniques to a group of 150 citrus fruit growers from five different communities in Veracruz, Mexico, to improve the adoption of social and technological innovations, their income, and profitability. The percentage of adoption of innovations (PAI) was calculated using the equation: PAI = n/N × 100, where n was the number of innovations adopted by the grower and N the total number of innovations available in the technological package. Two previous surveys, social and technological, were conducted in 2012 and revealed a significant lack of coordination in innovation networks, mainly in deep relationships, and little use of technological innovations. After the andragogic training and extension, better coordination was achieved, reflected in numerous and robust links, more nodes, and higher density, especially at the level of trust, contributing to consolidating social networks for 2014. The most adopted technological category was fertilization management. A survey was conducted in 2016 to quantify the permanence of the adoption of innovations. We conclude that social and technological intervention through andragogic training and extension improved the yield of orchards by more than 50 %, increased the income of citrus fruit growers 4.5 times, and consolidated workgroups and the permanence of innovations.

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In order to prevent gas leakage, gas sensors are routinely deployed in chemical industrial parks to monitor it. However, because of the effects of weather conditions, such as wind speed and direction, these gas sensors may not be able to accurately monitor the concentration of the gas leak. Toxic and harmful gases not only do harm to the surrounding environment, but also to the health of nearby residents. In order to effectively monitor the occurrence of gas leakage, in this paper, a plan of setting up wireless sensor network on site is designed, which is based on the meteorological and gas characteristics. What's more, the plan includes the rectangle plan, the fan plan and the annular plan. Also, it stipulates the optimization standard of sensor node position and deployment scheme and field experiments were carried out in the chemical industrial park, whereby the monitoring values of gas concentration in different schemes were obtained. According to the standards, the optimal deployment scheme and the optimal location of sensor nodes in different schemes are also procured. The results show that the method is feasible and effective. It can optimize the deployment position of different elevation under certain wind speed and wind direction as well as optimize different solutions. [ABSTRACT FROM AUTHOR]

For the 30,000 km long French conventional railway lines (94% of the whole network), the train speed is currently limited to 220 km/h, whilst the speed is 320 km/h for the 1800 km long high-speed lines. Nowadays, there is a growing need to improve the services by increasing the speed limit for the conventional lines. This paper aims at studying the influence of train speed on the mechanical behaviours of track-bed materials based on field monitoring data. Emphasis is put on the behaviours of interlayer and subgrade soils. The selected experimental site is located in Vierzon, France. Several sensors including accelerometers and soil pressure gauges were installed at different depths. The vertical strains of different layers can be obtained by integrating the records of accelerometers installed at different track-bed depths. The experimentation was carried out using an intercity test train running at different speeds from 60 km/h to 200 km/h. This test train was composed of a locomotive (22.5 Mg/axle) and 7 “Corail” coaches (10.5 Mg/axle). It was observed that when the train speed was raised, the loadings transmitted to the track-bed increased. Moreover, the response of the track-bed materials was amplified by the speed rise at different depths: the vertical dynamic stress was increased by about 10% when the train speed was raised from 60 km/h to 200 km/h for the locomotive loading, and the vertical strains doubled their quasi-static values in the shallow layers. Moreover, the stress–strain paths were estimated using the vertical stress and strain for each train speed. These loading paths allowed the resilient modulus Mr to be determined. It was found that the resilient modulus (Mr) was decreased by about 10% when the train speed was increased from 100 km/h to 200 km/h. However, the damping ratio (Dr) kept stable in the range of speeds explored.

Climate change and cotton production in Senegal: alternate dissemination strategies of varieties. Description of the subject. Climate change challenges the strategy of varietal diffusion, employed by the Senegalese cotton company (SODEFITEX), based on the distinction of two cultivars: one adapted to humid conditions and the other to drought. Based on data collected in an experimental station and farmer plots from 2004 to 2011, the study provides an assessment of that strategy. Objectives. The aim of the study was to evaluate both the methodology used for varietal selection and the performance of released and candidate cultivars, under contrasted water environments due to variability in rainfall (spatial and temporal) and crop management. Method. The methodology used allowed the identification of the occurrence of severe water stress during the critical cotton development phases (flowering and boll development) and its effect on seed cotton yield and fiber quality. The resulting indicator of plant water status was then inserted into our statistical analysis as an environmental covariate. Results. The resulting indicator allowed the discrimination of seed cotton yield in the experimental station as well as in on-farm experiments. Despite an effect of cultivar on ginning outturn and fiber quality, all cultivars showed similar resilience to water status. Conclusions. Despite a lack of cultivar adaptation to water stress, results support the adoption of a single cultivar in the whole production basin. However, the diffusion strategy would benefit from a better consideration of farmer cropping conditions, which would thus allow for the evaluation of cultivars by the producers.

Turnover of deep organic carbon in cultivated soils: an estimate from a review of isotope data. Description of the subject. This study is an estimate of medium-term renewal (decades) of deep carbon in cultivated soils. Objectives. Sequestration of organic carbon in soils is a way to mitigate the global rise in CO2 and warming. Deep horizons (> 30 cm) contain about half of the soil organic carbon but, in agriculture, deep organic carbon and nitrogen are often neglected when the balance of these elements is calculated. Our goal in this study was to propose a quantification of deep C turnover. Method. We collected data from 41 profiles, where C turnover was studied using the natural 13C labeling technique. The studied cropping systems were basically tropical and temperate C4 plant monocultures. Results. Deep carbon (30 – 100 cm) turnover was on average four times slower than in topsoil (0 – 30 cm), but renewal was significant. The average depth-distribution of the carbon flux to organic matter build-up was 81% in the layer at the 0 – 30 cm level and 19% in the layer at 30 – 100 cm, with a standard error of ± 4%. Over the longer term (20 years), subsoil at 30 – 100 cm contained on average 23% of the recent soil carbon accumulated in the first meter. Conclusions. Deep organic matter should not be overlooked when considering the balance of C and N and we therefore propose a simple method for an initial first assessment. In the future, further estimates of the temporal evolution of the deep carbon stock and its factors of variation should be based on long-term agronomic experiments or modeling parameterized on heavily instrumented sites, and should be accompanied by detailed pedological descriptions.

Description of the subject. The geographic distributions of a species, be it native or alien, is expected to be limited at some point by environmental conditions. In this situation, a range edge equilibrium (REE) takes place, i.e., populations occurring beyond the edge have a growth rate reduced below replacement. The occurrence of REE has never been tested for an invasive species. In Western Europe, the invasive weed Ambrosia artemisiifolia L. has spread in most parts of southern and central France, where it can be found in very high densities in sunflower fields, but seems to be limited in its northwards expansion. It is currently unknown whether the range has reached a limit or not. Information about how the species responds to sunflower competition is also lacking. Objectives. This work addressed two questions: Has the northern part of A. artemisiifolia invaded range in Western Europe reached REE? How is A. artemisiifolia performance influenced by sunflower competition? Method. Plots were established in an agricultural field ca. 250 km north to the current invaded range, in Belgium. We planted A. artemisiifolia seedlings with or without sunflower competition. The following year, the population growth rates and the soil seed bank were assessed. Results. The species established populations with relatively high growth rates and soil seed bank. Sunflower competition did not have a significant impact on plant performance. Conclusions. The results invalidate the hypothesis of equilibrium at the current margin of A. artemisiifolia invaded range, and suggest a significant potential for invasion northwards.

Fresh market apple harvesting is a difficult task that relies entirely on manual labor. Much research has been done on the development of mechanical harvesting techniques. Several selective harvesting robots have been developed for research studies, but there are no commercially available robotic systems. This article discusses the design and development of a novel pneumatic 3D-printed soft-robotic end-effector to facilitate apple separation. The end-effector was integrated into a robotic system with five degrees of freedom that was designed to simplify the picking sequence and reduce costs compared to previous versions. Apples were successfully harvested using the low-cost robotic system in a commercial orchard during the fall 2017 harvest. A detachment success rate on attempted apples of 67% was achieved, with an average time of 7.3 s per fruit from separation to storage bin. By conducting this study in an orchard where problematic apples were not removed to increase the detachment success rate, current pruning and thinning practices were assessed to help lay the foundation for future studies and develop strategies for successfully harvesting apples that are difficult to detach. [ABSTRACT FROM AUTHOR]

Abstract: This study presents the electromechanical design, the control approach, and the results of a field test campaign with the hybrid wheeled‐leg rover SherpaTT. The rover ranges in the 150 kg class and features an actively articulated suspension system comprising four legs with actively driven and steered wheels at each leg’s end. Five active degrees of freedom are present in each of the legs, resulting in 20 active degrees of freedom for the complete locomotion system. The control approach is based on force measurements at each wheel mounting point and roll–pitch measurements of the rover’s main body, allowing active adaption to sloping terrain, active shifting of the center of gravity within the rover’s support polygon, active roll–pitch influencing, and body‐ground clearance control. Exteroceptive sensors such as camera or laser range finder are not required for ground adaption. A purely reactive approach is used, rendering a planning algorithm for stability control or force distribution unnecessary and thus simplifying the control efforts. The control approach was tested within a 4‐week field deployment in the desert of Utah. The results presented in this paper substantiate the feasibility of the chosen approach: The main power requirement for locomotion is from the drive system, active adaption only plays a minor role in power consumption. Active force distribution between the wheels is successful in different footprints and terrain types and is not influenced by controlling the body’s roll–pitch angle in parallel to the force control. Slope‐climbing capabilities of the system were successfully tested in slopes of up to 28° inclination, covered with loose soil and duricrust. The main contribution of this study is the experimental validation of the actively articulated suspension of SherpaTT in conjunction with a reactive control approach. Consequently, hardware and software design as well as experimentation are part of this study. [ABSTRACT FROM AUTHOR]

This article highlights current research into land and water resources, agroecosystems, and agricultural production systems published by the Natural Resources and Environmental Systems (NRES) community of ASABE journals (Transactions of the ASABE and Applied Engineering in Agriculture) in 2017. Context, scope, and key results of the published articles are reviewed and perhaps more importantly areas for increased research attention are recommended. This article describes experimental and modeling advances in hydrology, agroecosystems, climate change effects, soil erosion, agricultural irrigation, agricultural drainage, forest resource management, livestock systems, natural treatment systems, international water issues, and water quality topic areas. Three special collections were published (International Watershed Technology, Crop Modeling and Decision Support for Optimizing Use of Limited Water, and Advances in Drainage). Other focal areas included 14 articles relating to livestock waste management, 13 concerning irrigated agricultural systems, 8 addressing climate change effects on land, water, and agroecosystems, and 16 on various aspects of soil erosion measurement and modeling. Building on the articles reviewed from 2017 and toward a vision of future agroecosystems research, the NRES community of ASABE journals strives to expand its role in making new knowledge accessible to sustain agricultural and natural systems in a changing world. With this goal in mind, recommendations for future research needs are proposed with an emphasis on increased application of remote sensing data to agroecosystems research, improved assessment of agroecosystem resiliency and vulnerability to land and climate change, development of integrated models of agroecosystem services, meeting stubborn water management challenges in agricultural production systems, and focusing on publishing fully reproducible model results. [ABSTRACT FROM AUTHOR]

Although small starfish may exert significant grazing effects on hard substrata, quantification of these effects has been difficult because of methodological limitations. Previously, caging small starfish for field experiments has failed because animals can escape through cage meshes and confounding effects may arise as the starfish can feed on organisms growing on the fences themselves, rather than the surface under investigation. Here, we investigated the efficiency of alternative barrier methods, such as antifouling paint and sticky barriers, for shorter-term experimental manipulation of the herbivorous starfish Parvulastra exigua. Laboratory and field manipulations tested the hypotheses that barriers are efficient in retaining starfish within plots and that the chemical repellent of the barriers does not affect the normal functioning of starfish. The results showed that the sticky barrier did not deter P. exigua, but antifouling paint retained greater numbers of individuals within barrier plots than in controls, with no short-term effects on starfish righting response. [ABSTRACT FROM AUTHOR]

This paper presents a study of the implementation of Participatory Plant Breeding in Cuba, a methodology based on the experience gained by a group of researchers, farmers and technicians. The proposal presents in materials and methods the four fundamental phases of this process: 1) Diagnosis, 2) Collection of plant genetic resources, 3) Establishments of demonstration plots and development of diversity fairs and 4) Peasant experimentation; The structure provides the necessary flexibility that will allow a proper application of the method and follows a logical order of the activities to be executed in a way that facilitates its execution in the different contexts in which it is of interest to apply it. It was obtained as a result that in addition to the four basic stages of Participative Plant breeding, other tools were used that allowed a successful process, they were: action learning according to interests, Farmers' schools, Innovation festivals, Exchange visits and coexistence, Training of students' capacities in the local innovation scenarios and creation of local seed banks. [ABSTRACT FROM AUTHOR]

This study focused on greening designs for building openings. Field experimentation was conducted and Computational Fluid Dynamics (CFD) software was used for simulation in order to analyze the influence of different greening design modes on indoor temperature. A greening design mode suitable for the opening of houses in Kaohsiung was proposed. This study took an architectural space with a pitched roof as the experimental site, where the main variable was the location of the plant facade outside the opening, and the distance between the plant and wall surface, as well as the number of plant layers, was the control variable. A plant (Rose of China) was selected for experimentation, and the indoor temperature distributions under various research module settings were discussed by numerical simulation. The conclusions are described, as follows: (1) The air temperature would be affected by the plants, and the indoor air temperature is reduced (over 0.5°C without direct sunshine in this study). (The difference between the indoor cooling effects with and without plants was 0.89~1.11°C. (2) While the cooling effect of the double-layer plant on indoor air temperature was better than a single-layer plant, the difference was limited and not proportional. (3) The plants should be located as close to the opening as possible, and be arranged partially sparse and partially dense. (4) When the outside wind speed is low, plant greening is highly recommended for cooling. [ABSTRACT FROM AUTHOR]

In the financial year 2009/10, the Great Britain (GB) rail infrastructure manager, Network Rail, spent £32 million on the failures within switches and crossings. Approximately 53% of those failures occurred within the switch panel. In addition, two major incidents in GB in recent years have highlighted a lack of understanding of the loads and vibrations experienced by, and the consequent rates of deterioration of, switch panels. This paper describes work which has been undertaken to help improve understanding of in-service loads experienced by switch panels and their consequent deterioration rate. Field experimentation has been designed and installed on four sites around GB, with the same design of switch. The change in response to loading, and the rate of deterioration, of the switch panels at each site was monitored over time. The effect of the vehicles and the deterioration were analysed individually before a comparison between the four sites. The analysis from the strain gauge measurements showed that there was an increase in the variance and maximum strains generated on the stock rail with the switch closed compared to when the switch is open. Finite element analysis was used to validate variation recorded by the strain gauges under similar loads. [ABSTRACT FROM AUTHOR]

Field experiments were conducted during the winter seasons of 1998-1999, 1999-2000 and 2000-2001 at the semi-arid region in north of Jordan, to study the effect of seeding dates (14 January, 28 January and 12 February), seeding rates (50, 75 and 100 plants per metre), phosphorus levels (0, 17.5, 35.0 and 52.5 kg P per ha) and two methods of P placement (banding and broadcast). Seeding rate, seeding date, and rate of phosphorus had a significant effect on most of the measured traits and the yield determinates. Method of phosphorus application had only a significant effect on seed yield and seed weight per plant. In general high yields were obtained by early seeding (14 January), high seeding rate (100-plant per square metre), and P application (52.5 kg P per ha) drilled with the seed after cultivation (banded).

[fr] On étudie la dynamique d'érosion de la surface du sol dans quelques versants de montagne de la source de la Ribera Salada (bassin du Sègre) en testant les modèles EROSION2D et EUROSEM. Trois usages du sol ont été différenciés: (1) Sous-bois du chêne pubescent, (2) terrasses agricoles et (3) bordures de buissons. En ce qui concerne le plan d'expérimentation, pendant six mois des épisodes climatiques naturels ont été contrôlés à l'aide d'un pluviographe et quinze parcelles à des canaux Gerlach. D'autre part, on a étudié des épisodes de haute intensité de precipitations grâce à six simidations de pluie. En outre, ont été réalisées les mesures topographiques, les échantillons et les experimentations nécessaires pour caractériser hydrologiquement la région et appliquer ainsi les modèles d'érosion choisis. Les conclusions principales sont les suivantes: a) des volumes très basses d'écoulement et d'érosion ont été observées et on a pu percevoir l'importance des flux hortoniens, facteur qui conditionne l'usage de ces modèles; b) le modèle E2D ne permet pas l'étude des épisodes d'intensités aussi faibles que ceux observés, et son application devrait être limitée aux terrains les moins poreux; c) l'application directe du modèle EUROSEM conduit à des erreurs considérables. On a calibré un paramètre pour réduire l'erreur dans le calcul de l'écoulement, et d) l'étude de la variabilité de l'humidité initiale du sol est extrêmement importante dans la modélisation de ces processus. [es] Se estudia la dinámica de erosión por escorrentía superficial en unas laderas montañosas de la cabecera de la Ribera Salada (cuenca del Sagre), distinguiendo tres usos de suelo: (1) sotobosque de quejigo, (2) terrazas agrícolas y (3) márgenes de matorral. Se analiza la aplicabilidad de los modelos Erosion2D y EUROSEM. En cuanto al diseño experimental, durante seis meses se controlaron episodios naturales mediante un pluviógrafo y quince parcelas con canales Gerlach. Se realizaron, asimismo, seis simulaciones de lluvia que permitieron estudiar episodios de alta intensidad. De manera complementaria se llevaron a cabo las mediciones topográficas, los muestreos y las experimentaciones necesarias para caracterizar hidrológicamente la zona y aplicar los modelos de erosión. Como principales conclusiones se pueden señalar las siguientes: a) las tasas de escorrentía y erosión registradas fueron muy bajas, y se constató la importancia de procesos diferentes al flujo hortoniano, lo cual condiciona el uso de estos modelos, b) el modelo E2D no permite estudiar episodios de baja magnitud como los registrados, y su aplicación se debería restringir a terrenos menos porosos, c) la aplicación directa del modelo EUROSEM origina errores importantes; se ha calibrado un parámetro para reducir el error en el cálculo de la escorrentía, y d) el estudio de la variabilidad de la humedad precedente del suelo resulta de gran importancia para la modelización de estos procesos.

This article explores the use of field experimentation in presenting an account of input inventory, material quantities, and the process flow for shea butter production in Ghana. The shea fruit is a non-timber forest product (NTFP) that is indigenous to ecosystems in semi-arid regions of Africa. Current methods and equipment for processing shea kernel into butter impose a dilemma of excessive harvesting of fuel wood for heating and the use of large quantities of water. Thus, the nature of input requirement and production process presents implications for conflict over natural resource use and for sustainability as more processing takes place. Material flow analysis was applied to the data generated from the processing experiments. The outcome was discussed in focus group discussion sessions and individual interviews as a way of data triangulation to validate study parameters. Results from this experiment showed that the quantity of water used in urban processing sites was higher than that used in rural sites. On the other hand, fuel wood use and labor expended were found to be higher in rural sites per unit processing cycle. The nature of the processing equipment, accessibility to input resources, and target market for shea butter were key determinants of the varying resource quantities used in the production process. [ABSTRACT FROM AUTHOR]