Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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De energiesector als lichtend of verblindend voorbeeld?
Giezen, M. ; Brouwer, Stijn ; Roest, Kees ; Vliet, B.J.M. van - \ 2017
H2O online (2017). - 6 p.
energie - water - hernieuwbare energie - systemen - economie - energy - renewable energy - systems - economics
De energiesector wordt in de watersector veelvuldig genoemd als voorbeeld voor de transitie richting een circulaire economie. In hoeverre werkt dit verhelderend of juist verblindend? In deze literatuurstudie laten de auteurs hun licht schijnen op de energiesector als voorbeeld wanneer het gaat om de introductie van nieuwe decentrale technieken. Vanuit zowel een technologisch, economisch, sociaal-cultureel als een institutioneel perspectief brengen de auteurs de contextuele systeemveranderingen die van invloed kunnen zijn op toepassing van decentrale technieken in kaart. Hiermee worden de overeenkomsten en verschillen tussen energie- en watersectoren helder en ontstaat ruimte voor relativering en nuance.
Agent-Based Modeling: A Powerful Tool for Tourism Researchers
Nicholls, Sarah ; Amelung, B. ; Student, Jillian - \ 2017
Journal of Travel Research 56 (2017)1. - ISSN 0047-2875 - p. 3 - 15.
agent-based modeling - complexity - simulation - systems - tourism
Agent-based modeling (ABM) is a way of representing complex systems of autonomous agents or actors, and of simulating the multiple potential outcomes of these agents’ behaviors and interactions in the form of a range of alternatives or futures. Despite the complexity of the tourism system, and the power and flexibility of ABM to overcome the assumptions such as homogeneity, linearity, equilibrium, and rationality typical of traditional modeling techniques, ABM has received little attention from tourism researchers and practitioners. The purpose of this paper is to introduce ABM to a wider tourism audience. Specifically, the appropriateness of tourism as a phenomenon to be subjected to ABM is established; the power and benefits of ABM as an alternative scientific mechanism are illuminated; the few existing applications of ABM in the tourism arena are summarized; and, a range of potential applications in the areas of tourism planning, development, marketing and management is proposed.
Self-assembly in a near-frictionless granular material: Conformational structures and transitions in uniaxial cyclic compression of hydrogel spheres
Walker, D.M. ; Tordesillas, A. ; Brodu, N. ; Dijksman, J.A. ; Behringer, R.P. ; Froyland, G. - \ 2015
Soft Matter 11 (2015). - ISSN 1744-683X - p. 2157 - 2173.
force chains - packing - systems - shear - continuum - networks - matter
We use a Markov transition matrix-based analysis to explore the structures and structural transitions in a three-dimensional assembly of hydrogel spheres under cyclic uniaxial compression. We apply these methods on experimental data obtained from a packing of nearly frictionless hydrogel balls. This allows an exploration of the emergence and evolution of mesoscale internal structures — a key micromechanical property that governs self-assembly and self-organization in dense granular media. To probe the mesoscopic force network structure, we consider two structural state spaces: (i) a particle and its contacting neighbours, and (ii) a particle's local minimal cycle topology summarized by a cycle vector. In both spaces, our analysis of the transition dynamics reveals which structures and which sets of structures are most prevalent and most likely to transform into each other during the compression/decompression of the material. In compressed states, structures rich in 3-cycle or triangle topologies form in abundance. In contrast, in uncompressed states, transitions comprising poorly connected structures are dominant. An almost-invariant transition set within the cycle vector space is discovered that identifies an intermediate set of structures crucial to the material's transition from weakly jammed to strongly jammed, and vice versa. Preferred transition pathways are also highlighted and discussed with respect to thermo-micro-mechanical constitutive formulations.
Caterpillar-inspired design and fabrication of a self-walking actuator with anisotropy, gradient, and instant response
Li, B. ; Du, T. ; Yu, B. ; Gucht, J. van der; Zhou, F. - \ 2015
Small 11 (2015)28. - ISSN 1613-6810 - p. 3494 - 3501.
transfer radical polymerization - polyelectrolyte brushes - thin-films - driven - contraction - expansion - bilayers - solvent - devices - systems
A caterpillar–mimetic bilayer actuator is reported, based on a wrinkled polydimethylsiloxane elastomer decorated with a hydroresponsive polyelectrolyte brush. The actuator can fold ultrafast into complex three-dimensional structures upon a change in relative humidity of the surrounding air. The folding direction is determined by the geometry of the actuator, the orientation of the wrinkles, and the gradient in polymer height on the surface. And some unique structures such as helicoid and gradient can be obtained that are seldom reported in the case of bilayered devices. The adaptive bending movement is very fast, anisotropic, highly efficient, and reversible. When the environmental humidity is repeatedly cycled up and down, the small device walks on a surface with a roughness gradient, which is reminiscent of the muscle-like movements.
Disciplines in the field of communication for development and social change
Lie, R. ; Servaes, J. - \ 2015
Communication Theory 25 (2015)2. - ISSN 1050-3293 - p. 244 - 258.
natural-resource management - innovation networks - perspective - systems
This article provides an overview of subdisciplines in the field of Communication for Development and Social Change. Different subdisciplines of communication science are analyzed to assess their connection to the field. Building on these subdisciplines the article reviews health communication, agricultural extension and rural communication, and environmental communication as practice-based subdisciplines of Communication for Development and Social Change. By assessing the current development and communication approaches within the different subdisciplines, the article aims to better understand the current state-of-the-art of the field and identify future imperatives.
Leverages for on-farm innovation from farm typologies? An illustration for family-based dairy farms in north-west Michoacán, Mexico
Cortez Arriola, J. ; Rossing, W.A.H. ; Amendola Massiotti, R.D. ; Scholberg, J.M.S. ; Groot, J.C.J. ; Tittonell, P.A. - \ 2015
Agricultural Systems 135 (2015). - ISSN 0308-521X - p. 66 - 76.
impact assessment - management - diversity - systems - scale - indicators - households - migration
Knowledge on farm diversity provides insight into differences among farms, enables scaling from individual farm to farm population level and vice versa, and has been used in the definition of recommendation domains for introduction of novel technologies. Farm diversity can be broadly described in terms of resource endowment and resource use strategy, or in other words, in terms of scale and intensity of production. Measuring intensity of production requires much greater monitoring effort than measuring scale of production, and often only proxies of production intensity are used. Using data from a regional farm survey and from intensive on-farm monitoring the question addressed in this paper is to which extent results of farm surveys that measure primarily scale of production can inform on-farm interventions aimed at improving farm performance. The survey included a random sample of 97 out of 664 smallholder dairy farmers in a community in north-west Michoacán, Mexico. Farm types were identified by a combination of Principal Component Analysis to reduce the dimensionality of the dataset, followed by Cluster Analysis. The survey was complemented with detailed analyses of costs, revenues and productivity on 6 farms over the course of one year. Survey results revealed considerable variation among the dairy farms in land area, livestock units, amount of hired labour, and infrastructure and equipment, which led to the distinction of 4 farm types. Indicators for animal health management and feeding strategies were uniform across the 4 types. The farm types matched the distinction of family-based and semi-intensive farm types used in Mexico. The detailed analyses of the individual farms belonging to the different types, however, revealed differences in resource use strategies reflected in differences in animal productivity, labour productivity and return to labour. Differences in animal productivity and labour productivity were explained by stocking rate, albeit in different ways. Return to labour was strongly related to cost of feed. Profitability was negative for all farms and was on most farms related to high external feedstuff costs, which constituted 59–89% of the feed cost of the animal ration. The results indicate that in addition to variables reflecting resource endowment or scale of production, typologies that aim to inform on-farm interventions need to consider farm characteristics that reflect intensity of production. Which variables should be selected will need to be determined in a preliminary assessment. To enhance internal resource use efficiency as was the purpose in the current study, candidate variables expressing intensity could include the share of external feed in the ration and proxies of internal resource use, e.g. reflected in crop and milk yields. Opportunities for on-farm innovation arising from the analyses are discussed from the perspective of labour flexibility, low costs and use of internal resources.
Modeling an inventory routing problem for perishable products with environmental considerations
Soysal, M. ; Bloemhof, J.M. ; Haijema, R. ; Vorst, J.G.A.J. van der - \ 2015
International Journal of Production Economics 164 (2015). - ISSN 0925-5273 - p. 118 - 133.
service-level constraints - transshipment - heuristics - systems - stock - time
The transition to sustainable food supply chain management has brought new key logistical aims such as reducing food waste and environmental impacts of operations in the supply chain besides the traditional cost minimization objective. Traditional assumptions of constant distribution costs between nodes, unlimited product shelf life and deterministic demand used in the Inventory Routing Problem (IRP) literature restrict the usage of the proposed models in current food logistics systems. From this point of view, our interest in this study is to enhance the traditional models for the IRP to make them more useful for the decision makers in food logistics management. Therefore, we present a multi-period IRP model that includes truck load dependent (and thus route dependent) distribution costs for a comprehensive evaluation of CO2 emission and fuel consumption, perishability, and a service level constraint for meeting uncertain demand. A case study on the fresh tomato distribution operations of a supermarket chain shows the applicability of the model to a real-life problem. Several variations of the model, each differing with respect to the considered aspects, are employed to present the benefits of including perishability and explicit fuel consumption concerns in the model. The results suggest that the proposed integrated model can achieve significant savings in total cost while satisfying the service level requirements and thus offers better support to decision makers.
Organising a safe space for navigating social-ecological transformations to sustainability
Pereira, L. ; Karpouzoglou, T.D. ; Doshi, S. ; Frantzeskaki, N. - \ 2015
International Journal of Environmental Research and Public Health 12 (2015)6. - ISSN 1660-4601 - p. 6027 - 6044.
transitions - innovation - framework - systems - perspective - governance - complexity - knowledge - responses - pathways
The need for developing socially just living conditions for the world’s growing population whilst keeping human societies within a ‘safe operating space’ has become a modern imperative. This requires transformative changes in the dominant social norms, behaviours, governance and management regimes that guide human responses in areas such as urban ecology, public health, resource security (e.g., food, water, energy access), economic development and biodiversity conservation. However, such systemic transformations necessitate experimentation in public arenas of exchange and a deepening of processes that can widen multi-stakeholder learning. We argue that there is an emergent potential in bridging the sustainability transitions and resilience approaches to create new scientific capacity that can support large-scale social-ecological transformations (SETs) to sustainability globally, not just in the West. In this article, we elucidate a set of guiding principles for the design of a ‘safe space’ to encourage stronger interactions between these research areas and others that are relevant to the challenges faced. We envisage new opportunities for transdisciplinary collaboration that will develop an adaptive and evolving community of practice. In particular, we emphasise the great opportunity for engaging with the role of emerging economies in facilitating safe space experimentation.
Stochastic uncertainty and sensitivities of nitrogen flows on diary farms in The Netherlands
Oenema, J. ; Burgers, S. ; Keulen, H. van; Ittersum, M.K. van - \ 2015
Agricultural Systems 137 (2015). - ISSN 0308-521X - p. 126 - 138.
manure management-practices - nutrient management - use efficiency - systems - balances - budgets - losses - europe
Nutrient management decisions and environmental policy making must be based on sound data and proper analysis. Annual data collection and monitoring of farm and nutrient performance are wrought with uncertainties. Such uncertainties need to be addressed as it may lead to ambiguities and wrong conclusions. We developed an input-output N balance model to describe and quantify N flows in dairy farming systems. Input for this model was based on monitored data for one year (2005) from one experimental (detailed monitoring) and 14 pilot commercial dairy farms (less detailed monitoring). A Monte Carlo approach was used to quantify effects of uncertainty of input data on annual farm N surplus, soil surface N surplus and N intake during grazing, followed by a sensitivity analysis to apportion the different sources of uncertainty. Uncertainties in data input were described with probability density functions. Farm N surplus of the 14 pilot farms ranged between 81 and 294¿kg¿ha-1, soil surface N surplus between 35 and 256¿kg¿ha-1, and N intake during grazing between 27 and 108¿kg¿ha-1. The uncertainties of N flows – both relative and absolute – increased from farm N surplus (CV¿=¿8%; SD¿=¿15¿kg¿N¿ha-1) to soil surface N surplus (CV¿=¿12%; SD¿=¿16¿kg¿N¿ha-1) to N intake during grazing (CV¿=¿49%; SD¿=¿28¿kg¿N¿ha-1). Variation in uncertainty among farms in farm and soil surface N surplus and N intake during grazing was substantial and was related to the farm structure and farm characteristics such as production intensity, N fixation by clover and annual changes in stocks of roughage and manure. We found that a monitoring program based on more measurements instead of estimates and/or fixed rate values from literature will not always result in a better quantification of farm and soil surface N surplus on clover-based dairy farms. However, on farms with no N fixation, an intensive monitoring program reduced the uncertainty in farm and soil surface N surplus by 23% and the uncertainty of N intake during grazing was reduced by more than 30%. Knowledge about uncertainties of N flows is necessary to correctly interpret the N performance on dairy farms and its evolution through time. A first step is to get insights into the most uncertain N flows on a dairy farm. The next step, where possible, is to improve the estimation of the most uncertain N flows. Based on the insights from this study, these steps will underpin the validation of trends in N performance and justify decisions in environmental policy making and/or decisions for making on-farm improvements.
Spatially explicit fate modelling of nanomaterials in natural waters
Quik, J.T.K. ; Klein, J.J.M. de; Koelmans, A.A. - \ 2015
Water Research 80 (2015). - ISSN 0043-1354 - p. 200 - 208.
engineered nanomaterials - aquatic environments - nanoparticles - aggregation - systems - exposure - sedimentation - calibration - matrices - silver
Site specific exposure assessments for engineered nanoparticles (ENPs) require spatially explicit fate models, which however are not yet available. Here we present an ENP fate model (NanoDUFLOW) that links ENP specific process descriptions to a spatially explicit hydrological model. The link enables the realistic modelling of feedbacks between local flow conditions and ENP fate processes, such as homo- and heteroaggregation, resuspension and sedimentation. Spatially explicit simulations using five size classes of ENPs and five size classes of natural solids showed how ENP sediment contamination ‘hot spots’ and ENP speciation can be predicted as a function of place and time. For the catchment modelled, neglect of spatial heterogeneity caused relatively small differences in ENP retention. However, simplification of the number of size classes to one average class, resulted in up to 3.3 times lower values of retention compared to scenarios that used detailed size distributions. Local concentrations in sediment were underestimated up to 20 fold upon simplification of spatial heterogeneity or particle size distribution. We conclude that spatial heterogeneity should not be neglected when assessing the risks of ENPs.
Participatory appraisal of institutional and political constraints and opportunities for innovation to address parasitic weeds in rice
Schut, M. ; Rodenburg, J. ; Klerkx, L.W.A. ; Hinnou, L.C. ; Kayeke, J. ; Bastiaans, L. - \ 2015
Crop Protection 74 (2015). - ISSN 0261-2194 - p. 158 - 170.
fed lowland rice - striga-hermonthica control - raais rapid appraisal - sub-saharan africa - socioeconomic constraints - integrated analysis - pest-management - systems - benin - tanzania
Parasitic weeds in smallholder rice production systems, of which Striga asiatica, Striga hermonthica and hamphicarpa fistulosa are the main representatives, form an increasing problem for food and income security in sub-Saharan Africa (SSA). The objective of this paper is to identify institutional and political constraints and opportunities for innovation to address parasitic weed problems in rice. Constraints and opportunities for innovation were studied across three nested systems: the parasitic weed control system, the crop protection system, and the agricultural system. Multi-stakeholder workshops, interviews and surveys were held to gather data on key constraints faced by different stakeholder groups across three parasitic weed infested study sites in both Tanzania and Benin. The results demonstrate that in both countries, the majority of institutional and political constraints relate to the functioning of the broader crop protection and agricultural systems and not specifically to parasitic weeds. Although differences were observed between the two countries and the different stakeholder groups, the majority of constraints perceived by the stakeholders were caused by a lack of capabilities and resources and a limited access to credit. Awareness raising of parasitic weed problems among farmers, extension and crop protection officers at the local level, combined with improved input and service supply and enhanced agricultural education and training curricula at the national level, were identified as important elements for improvement. More structural collaboration between key stakeholder groups is expected to contribute to a better recognition of agricultural problems, like that of parasitic weeds in rice, and a more timely identification of feasible solutions.
From field to atlas: Upscaling of location-specific yield gap estimates
Bussel, L.G.J. van; Grassini, P. ; Wart, J. van; Wolf, J. ; Claessens, L. ; Yang, H. ; Boogaard, H.L. ; Groot, H.L.E. de; Saito, K. ; Cassman, K.G. ; Ittersum, M.K. van - \ 2015
Field Crops Research 177 (2015). - ISSN 0378-4290 - p. 98 - 108.
climate-change - weather data - crop yields - input data - resolution - model - scale - impact - maize - systems
Accurate estimation of yield gaps is only possible for locations where high quality local data are available,which are, however, lacking in many regions of the world. The challenge is how yield gap estimates basedon location-specific input data can be used to obtain yield gap estimates for larger spatial areas. Hence,insight about the minimum number of locations required to achieve robust estimates of yield gaps atlarger spatial scales is essential because data collection at a large number of locations is expensive andtime consuming. In this paper we describe an approach that consists of a climate zonation scheme supple-mented by agronomical and locally relevant weather, soil and cropping system data. Two elements of thismethodology are evaluated here: the effects on simulated national crop yield potentials attributable tomissing and/or poor quality data and the error that might be introduced in scaled up yield gap estimatesdue to the selected climate zonation scheme. Variation in simulated yield potentials among weatherstations located within the same climate zone, represented by the coefficient of variation, served as ameasure of the performance of the climate zonation scheme for upscaling of yield potentials.We found that our approach was most appropriate for countries with homogeneous topography andlarge climate zones, and that local up-to-date knowledge of crop area distribution is required for selectingrelevant locations for data collection. Estimated national water-limited yield potentials were found to berobust if data could be collected that are representative for approximately 50% of the national harvestedarea of a crop. In a sensitivity analysis for rainfed maize in four countries, assuming only 25% coverageof the national harvested crop area (to represent countries with poor data availability), national water-limited yield potentials were found to be over- or underestimated by 3 to 27% compared to estimateswith the recommended crop area coverage of =50%. It was shown that the variation of simulated yieldpotentials within the same climate zone is small. Water-limited potentials in semi-arid areas are anexception, because the climate zones in these semi-arid areas represent aridity limits of crop productionfor the studied crops. We conclude that the developed approach is robust for scaling up yield gap estimatesfrom field, i.e. weather station data supplemented by local soil and cropping system data, to regional andnational levels. Possible errors occur in semi-arid areas with large variability in rainfall and in countrieswith more heterogeneous topography and climatic conditions in which data availability hindered full application of the approach.
Empty pockets, empty ponds? Disadoption of water harvesting technologies in Ethiopia
Wakeyo, M.B. ; Gardebroek, C. - \ 2015
Journal of Arid Environments 120 (2015). - ISSN 0140-1963 - p. 75 - 86.
supplemental irrigation - agricultural extension - semiarid region - adoption - systems - productivity - africa - impact - china - soil
This study analyses disadoption of water harvesting technologies in Ethiopia where the average disadiption rate in the sample areas is as high as 42%. Given that Ethiopia is a drought-prone country with 95% of its crop production being rain-fed, such a high disadoption rate for irrigation technologies is surprising and urges investigation. Using panel data on 332 Ethiopian farm households collected in 2005 and 2010 we estimate a logit model to identify factors underlying disadoption. We find farm-household, economic, technology-specific, and natural condition variables that relate to disadoption. Mainly, shortage of plastic-sheets, altitude, and distance to market increase disadoption whereas education, experience with water harvesting (learning-by-doing), farm profit, availability of family labour, access to credit, ease of selling output, growing perennial crops, and distance from natural water sources decrease the probability of disadiption. There is no evidence that malaria has a significant effect on disadoption. Based on these findings, improved supply of plastic sheets and motor pumps, and advise to afmers on appropriate crops, credit and improved market accesses could ontribute to decreasing disadoption of water harvesting technologies.
Responses of organic housed laying hens to dietary methionine and energy during a summer and winter season
Krimpen, M.M. van; Binnendijk, G.P. ; Ogun, M. ; Kwakkel, R.P. - \ 2015
British Poultry Science 56 (2015)1. - ISSN 0007-1668 - p. 121 - 131.
temperature - performance - requirements - consumption - behavior - systems - pullets - fowl
The main dietary challenge in organic laying hen production is to fulfil the digestible methionine (MET) requirement in a diet consisting of ingredients of organic origin only. The aim of the present experiment was to determine the response of organic housed laying hens (26–34 weeks of age) to dietary energy and MET during a summer and winter trial. Per trial, a total of 128 17-week-old Brown Nick hens were allotted to 16 pens, which were connected to an outdoor run. Each experiment comprised 8 dietary treatments according to a 4 × 2 factorial design. The factors were AFD MET level (2.3, 2.7, 3.1 and 3.5 g/kg) and energy content (10.9 and 12.1 MJ). Dietary energy content did not affect energy intake (1361 kJ/d) in summer, whereas energy intake in winter was increased in hens that were fed on the 12.1-MJ diets (1514 vs. 1421 kJ/d). Maximal egg mass in summer was achieved if a diet with 3.5 g/kg MET was given, corresponding to a digestible MET intake of 421 mg/d. During winter, maximal egg mass was achieved with a digestible MET intake of 360 mg/d, which was already realised with a MET content of 2.7 g/kg. Because digestible MET content for maximal egg performance differed between the summer and winter trial, dietary energy to MET ratio might be adjusted to seasonal conditions.
Two distinct groups within the Bacillus subtilis group display significantly different spore heat resistance properties
Berendsen, E.M. ; Zwietering, M.H. ; Kuipers, O.P. ; Wells-Bennik, M.H.J. - \ 2015
Food Microbiology 45 (2015). - ISSN 0740-0020 - p. 18 - 25.
thermal inactivation - bacterial-spores - sporulation - food - sporothermodurans - strains - systems - milk - stearothermophilus - temperatures
The survival of bacterial spores after heat treatment and the subsequent germination and outgrowth in a food product can lead to spoilage of the food product and economical losses. Prediction of time-temperature conditions that lead to sufficient inactivation requires access to detailed spore thermal inactivation kinetics of relevant model strains. In this study, the thermal inactivation kinetics of spores of fourteen strains belonging to the Bacillus subtilis group were determined in detail, using both batch heating in capillary tubes and continuous flow heating in a micro heater. The inactivation data were fitted using a log linear model. Based on the spore heat resistance data, two distinct groups (p <0.001) within the B. subtilis group could be identified. One group of strains had spores with an average D120 °C of 0.33 s, while the spores of the other group displayed significantly higher heat resistances, with an average D120 °C of 45.7 s. When comparing spore inactivation data obtained using batch- and continuous flow heating, the z-values were significantly different, hence extrapolation from one system to the other was not justified. This study clearly shows that heat resistances of spores from different strains in the B. subtilis group can vary greatly. Strains can be separated into two groups, to which different spore heat inactivation kinetics apply.
Agroecology as a vehicle for contributive justice
Timmermann, C. ; Felix, G.F. - \ 2015
Agriculture and Human Values 32 (2015)3. - ISSN 0889-048X - p. 523 - 538.
food sovereignty - meaningful work - intellectual property - green-revolution - agriculture - systems - labor - sustainability - need - capabilities
Agroecology has been criticized for being more labor-intensive than other more industrialized forms of agriculture. We challenge the assertion that labor input in agriculture has to be generally minimized and argue that besides quantity of work one should also consider the quality of work involved in farming. Early assessments on work quality condemned the deskilling of the rural workforce, whereas later criticisms have concentrated around issues related to fair trade and food sovereignty. We bring into the discussion the concept of contributive justice to welcome the added labor-intensity of agroecological farming. Contributive justice demands a work environment where people are stimulated to develop skills and learn to be productive. It also suggests a fairer distribution of meaningful work and tedious tasks. Building on the notion of contributive justice we explore which capabilities and types of social relationships are sustainably promoted and reinforced by agroecological farming practices. We argue that agroecological principles encourage a reconceptualization of farm work. Farmers are continuously stimulated to develop skills and acquire valuable experiential knowledge on local ecosystems and agricultural techniques. Further, generalized ecological studies recognize the significance of the farmer’s observations on natural resources management. This contributes to the development of a number of capabilities and leads to more bargaining power, facilitating self-determination. Hereby farm work is made more attractive to a younger generation, which is an essential factor for safeguarding the continuity of family farms.
Wirelessly powered ultraviolet light emitting diodes for photocatalytic oxidation
Kuipers, J. ; Bruning, H. ; Yntema, D.R. ; Rijnaarts, H.H.M. - \ 2015
Journal of Photochemistry and Photobiology. A, Chemistry 299 (2015). - ISSN 1010-6030 - p. 25 - 30.
heterogeneous photocatalysis - water-treatment - reactor - design - pollutants - systems
A method is presented to distribute small scale light sources in a photocatalytic slurry reactor. The goal of distributing the light sources is to increase photon transfer efficiency, and thereby increasing the reaction rate, compared to using one single light source. The light sources used in this study were ultraviolet light emitting diodes with a wavelength of 375 nm. An up-flow of air into the photocatalytic reactor distributes the UV-LEDs throughout the reactor, mixes the reaction solution and saturates the solution with molecular oxygen. To make distribution of the UV-LEDs possible, the UV-LEDs were powered wirelessly by resonant inductive coupling. This article shows that UV-LEDs distributed throughout the reactor show a 30% higher removal rate of methylene blue compared to the UV-LEDs concentrated on one plane in the reactor. The removal rate increased linearly with increasing numbers of UV-LEDs. The size of the UV-LEDs determined that up to 32 UV-LEDs could be wirelessly powered in a reactor volume of 500 ml. To increase the reactivity, a higher amount of UV-LEDs per reaction liquid volume and higher radiant power of the UV-LED can be used, bringing use of photocatalytic reactors closer to industrial applications.
Fatty acid and triglycerides profiling of retail organic, conventional and pasture milk: Implications for health and authenticity
Capuano, E. ; Gravink, R. ; Boerrigter-Eenling, G.R. ; Ruth, S.M. van - \ 2015
International Dairy Journal 42 (2015). - ISSN 0958-6946 - p. 58 - 63.
conjugated linoleic acids - coronary-heart-disease - fresh grass - dairy-products - cows - verification - metaanalysis - cholesterol - systems
Retail full fat high temperature short time pasteurised conventional, organic and “weidemelk” (Dutch quality label for milk from cows on pasture at least 6 h per day, 120 days per year) milk samples were collected on 2 sampling dates in winter and 4 sampling dates in summer 2013 and analysed for the fatty acid (FA) and the triglyceride (TAG) profile by gas chromatography-flame ionisation detection. FA profile of organic milk was significantly different from that of conventional and “weidemelk” milk both in summer and in winter and the differences between conventional and “weidemelk” milk were less remarkable or negligible. Analogously, the TAG profile of organic milk was different from that of the other two groups but the differences were weaker compared with FA profile. The differences in FA composition of retail full fat milk may have implications for consumers' health and may be used for the authentication of retail organic milk.
Nondestructive estimates of above-ground biomass using terrestrial laser scanning
Calders, K. ; Newnham, G. ; Burt, A. ; Murphy, S. ; Raumonen, P. ; Herold, M. ; Culvenor, D. ; Avitabile, V. ; Disney, M. ; Armston, J. ; Kaasalainen, M. - \ 2015
Methods in Ecology and Evolution 6 (2015)2. - ISSN 2041-210X - p. 198 - 208.
carbon-density - tree - lidar - models - equations - systems - volume - stocks
Allometric equations are currently used to estimate above-ground biomass (AGB) based on the indirect relationship with tree parameters. Terrestrial laser scanning (TLS) can measure the canopy structure in 3D with high detail. In this study, we develop an approach to estimate AGB from TLS data, which does not need any prior information about allometry. We compare these estimates against destructively harvested AGB estimates and AGB derived from allometric equations. We also evaluate tree parameters, diameter at breast height (DBH) and tree height, estimated from traditional field inventory and TLS data. Tree height, DBH and AGB data are collected through traditional forest inventory, TLS and destructive sampling of 65 trees in a native Eucalypt Open Forest in Victoria, Australia. Single trees are extracted from the TLS data and quantitative structure models are used to estimate the tree volume directly from the point cloud data. AGB is inferred from these volumes and basic density information and is then compared with the estimates derived from allometric equations and destructive sampling. AGB estimates derived from TLS show a high agreement with the reference values from destructive sampling, with a concordance correlation coefficient (CCC) of 0·98. The agreement between AGB estimates from allometric equations and the reference is lower (CCC = 0·68–0·78). Our TLS approach shows a total AGB overestimation of 9·68% compared to an underestimation of 36·57–29·85% for the allometric equations. The error for AGB estimates using allometric equations increases exponentially with increasing DBH, whereas the error for AGB estimates from TLS is not dependent on DBH. The TLS method does not rely on indirect relationships with tree parameters or calibration data and shows better agreement with the reference data compared to estimates from allometric equations. Using 3D data also enables us to look at the height distributions of AGB, and we demonstrate that 80% of the AGB at plot level is located in the lower 60% of the trees for a Eucalypt Open Forest. This method can be applied in many forest types and can assist in the calibration and validation of broad-scale biomass maps.
Farmers’ views on the future prospects of aerobic rice culture in Pakistan
Awan, M.I. ; Oort, P.A.J. van; Ahmad, R. ; Bastiaans, L. ; Meinke, H.B. - \ 2015
Land Use Policy 42 (2015). - ISSN 0264-8377 - p. 517 - 526.
agricultural technology - seeded rice - water-use - systems - irrigation - adoption - performance - growth - punjab - yield
In parts of Pakistan, the sustainability of conventional flooded rice systems is threatened by diminishingresources, particularly – land, water, and labour. The adoption of aerobic rice system (ARS), an alterna-tive to the conventional systems, could considerably increase resource-use efficiencies. Information onfarmer perceptions is vital to identify socio-technological factors of adoption. Our aim was to under-stand and analyse farmer perceptions about ARS in regards to future adoption. We conducted our studyin the Pakistani Punjab with three groups of farmers: (I) informant farmers in rice–wheat system whotrialled ARS in a participatory research trial (n = 70), (II) rice farmers in rice–wheat, mixed-cropping andcotton–wheat system with no experience of ARS (n = 97), and (III) non-rice farmers in mixed-croppingand cotton–wheat system (n = 48). Data were collected using a pretested semi-structured questionnaireand analysed by using descriptive statistics and chi-square tests. More than half of respondents in groupsII and III had never heard of ARS, though, 76% were open to experimenting. Across three groups, farmersperceived ARS as a means of increasing resource-use efficiency particularly for labour, net profitabil-ity, and an option for crop diversification in the mixed-cropping system. Perceived threats were weeds,diseases, poor germination, spikelet sterility, low yields, and frequent irrigation requirement. Decidingfactors for repeat ARS plantings by group I were: ease of operation due to direct seeding, good income,and low input requirement. Deciding factors against repeat plantings were: unavailability of suitable finegrain basmati varieties, falling water table, weed problem, and unsuitable soil type. The results suggestthat aerobic rice is an interesting alternative to traditional rice production as evident from the willingnessto plant again by 73% group I demonstration households but the unavailability of well-adapted basmativarieties hampers its expansion. Farmers’ appreciation of risks and benefits can pave the way for large-scale adoption. Associated risks can be reduced by filling the identified knowledge or technological gapsthrough additional research and farmer awareness programmes.
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