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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Introducing the urban wind island effect
Droste, A.M. ; Steeneveld, G.J. ; Holtslag, A.A.M. - \ 2018
Environmental Research Letters 13 (2018)9. - ISSN 1748-9318
meteorology - model - urban climate - urban weather - wind - wind island

Wind is a key component of the urban climate due to its relevance for ventilation of air pollution and urban heat, wind nuisance, as well as for urban wind energy engineering. These winds are governed by the dynamics of the atmosphere closest to the surface, the atmospheric boundary layer (ABL). Making use of a conceptual bulk model of the ABL, we find that for certain atmospheric conditions the boundary-layer mean wind speed in a city can surprisingly be higher than its rural counterpart, despite the higher roughness of cities. This urban wind island effect (UWI) prevails in the afternoon, and appears to be caused by a combination of differences in ABL growth, surface roughness and the ageostrophic wind, between city and countryside. Enhanced turbulence in the urban area deepens the ABL, and effectively mixes momentum into the ABL from aloft. Furthermore, the oscillation of the wind around the geostrophic equilibrium, caused by the rotation of the Earth, can create episodes where the urban boundary-layer mean wind speed is higher than the rural wind. By altering the surface properties within the bulk model, the sensitivity of the UWI to urban morphology is studied for the 10 urban local climate zones (LCZs). These LCZs classify neighbourhoods in terms of building height, vegetation cover etc, and represent urban morphology regardless of culture or location. The ideal circumstances for the UWI to occur are a deeper initial urban boundary-layer than in the countryside, low-rise buildings (up to 12 m) and a moderate geostrophic wind (∼5 m s-1). The UWI phenomenon challenges the commonly held perception that urban wind is usually reduced due to drag processes. Understanding the UWI can become vital to accurately model urban air pollution, quantify urban wind energy potential or create accurate background conditions for urban computational fluid dynamics models.

Resilience of tropical tree cover : The roles of climate, fire, and herbivory
Staal, Arie ; Nes, Egbert H. van; Hantson, Stijn ; Holmgren, Milena ; Dekker, Stefan C. ; Pueyo, Salvador ; Xu, Chi ; Scheffer, Marten - \ 2018
Global Change Biology 24 (2018)11. - ISSN 1354-1013 - p. 5096 - 5109.
alternative stable states - bistability - forest - grasslands - livestock - model - regime shifts - remote sensing - tipping points - wildfire

Fires and herbivores shape tropical vegetation structure, but their effects on the stability of tree cover in different climates remain elusive. Here, we integrate empirical and theoretical approaches to determine the effects of climate on fire- and herbivore-driven forest-savanna shifts. We analyzed time series of remotely sensed tree cover and fire observations with estimates of herbivore pressure across the tropics to quantify the fire–tree cover and herbivore–tree cover feedbacks along climatic gradients. From these empirical results, we developed a spatially explicit, stochastic fire-vegetation model that accounts for herbivore pressure. We find emergent alternative stable states in tree cover with hysteresis across rainfall conditions. Whereas the herbivore–tree cover feedback can maintain low tree cover below 1,100 mm mean annual rainfall, the fire–tree cover feedback can maintain low tree cover at higher rainfall levels. Interestingly, the rainfall range where fire-driven alternative vegetation states can be found depends strongly on rainfall variability. Both higher seasonal and interannual variability in rainfall increase fire frequency, but only seasonality expands the distribution of fire-maintained savannas into wetter climates. The strength of the fire–tree cover feedback depends on the spatial configuration of tree cover: Landscapes with clustered low tree-cover areas are more susceptible to cross a tipping point of fire-driven forest loss than landscapes with scattered deforested patches. Our study shows how feedbacks involving fire, herbivores, and the spatial structure of tree cover explain the resilience of tree cover across climates.

How do farm models compare when estimating greenhouse gas emissions from dairy cattle production?
Hutchings, N.J. ; Özkan Gülzari, Gülzari ; Haan, M. de; Sandars, D. - \ 2018
Animal 12 (2018)10. - ISSN 1751-7311 - p. 2171 - 2180.
dairy cattle - farm-scale - greenhouse gas - model
The European Union Effort Sharing Regulation (ESR) will require a 30% reduction in greenhouse gas (GHG) emissions by 2030 compared with 2005 from the sectors not included in the European Emissions Trading Scheme, including agriculture. This will require the estimation of current and future emissions from agriculture, including dairy cattle production systems. Using a farm-scale model as part of a Tier 3 method for farm to national scales provides a more holistic and informative approach than IPCC (2006) Tier 2 but requires independent quality control. Comparing the results of using models to simulate a range of scenarios that explore an appropriate range of biophysical and management situations can support this process by providing a framework for placing model results in context. To assess the variation between models and the process of understanding differences, estimates of GHG emissions from four farm-scale models (DairyWise, FarmAC, HolosNor and SFARMMOD) were calculated for eight dairy farming scenarios within a factorial design consisting of two climates (cool/dry and warm/wet)×two soil types (sandy and clayey)×two feeding systems (grass only and grass/maize). The milk yield per cow, follower:cow ratio, manure management system, nitrogen (N) fertilisation and land area were standardised for all scenarios in order to associate the differences in the results with the model structure and function. Potential yield and application of available N in fertiliser and manure were specified separately for grass and maize. Significant differences between models were found in GHG emissions at the farm-scale and for most contributory sources, although there was no difference in the ranking of source magnitudes. The farm-scale GHG emissions, averaged over the four models, was 10.6 t carbon dioxide equivalents (CO2e)/ha per year, with a range of 1.9 t CO2e/ha per year. Even though key production characteristics were specified in the scenarios, there were still significant differences between models in the annual milk production per ha and the amounts of N fertiliser and concentrate feed imported. This was because the models differed in their description of biophysical responses and feedback mechanisms, and in the extent to which management functions were internalised. We conclude that comparing the results of different farm-scale models when applied to a range of scenarios would build confidence in their use in achieving ESR targets, justifying further investment in the development of a wider range of scenarios and software tools.
Hemp (Cannabis sativa L.) leaf photosynthesis in relation to nitrogen content and temperature : implications for hemp as a bio-economically sustainable crop
Tang, Kailei ; Struik, Paul C. ; Amaducci, Stefano ; Stomph, Tjeerd Jan ; Yin, Xinyou - \ 2017
Global change biology Bioenergy 9 (2017)10. - ISSN 1757-1693 - p. 1573 - 1587.
Hemp (Cannabis sativa L.) - model - nitrogen - photosynthesis - sustainable crop - temperature

Hemp (Cannabis sativa L.) may be a suitable crop for the bio-economy as it requires low inputs while producing a high and valuable biomass yield. With the aim of understanding the physiological basis of hemp's high resource-use efficiency and yield potential, photosynthesis was analysed on leaves exposed to a range of nitrogen and temperature levels. Light-saturated net photosynthesis rate (Amax) increased with an increase in leaf nitrogen up to 31.2 ± 1.9 μmol m−2 s−1 at 25 °C. The Amax initially increased with an increase in leaf temperature (TL), levelled off at 25–35 °C and decreased when TL became higher than 35 °C. Based on a C3 leaf photosynthesis model, we estimated mesophyll conductance (gm), efficiency of converting incident irradiance into linear electron transport under limiting light (κ2 LL), linear electron transport capacity (Jmax), Rubisco carboxylation capacity (Vcmax), triose phosphate utilization capacity (Tp) and day respiration (Rd), using data obtained from gas exchange and chlorophyll fluorescence measurements at different leaf positions and various levels of incident irradiance, CO2 and O2. The effects of leaf nitrogen and temperature on photosynthesis parameters were consistent at different leaf positions and among different growth environments except for κ2 LL, which was higher for plants grown in the glasshouse than for those grown outdoors. Model analysis showed that compared with cotton and kenaf, hemp has higher photosynthetic capacity when leaf nitrogen is <2.0 g N m−2. The high photosynthetic capacity measured in this study, especially at low nitrogen level, provides additional evidence that hemp can be grown as a sustainable bioenergy crop over a wide range of climatic and agronomic conditions.

A meta-analysis of leaf nitrogen distribution within plant canopies
Hikosaka, Kouki ; Anten, Niels P.R. ; Borjigidai, Almaz ; Kamiyama, Chiho ; Sakai, Hidemitsu ; Hasegawa, Toshihiro ; Oikawa, Shimpei ; Iio, Atsuhiro ; Watanabe, Makoto ; Koike, Takayoshi ; Nishina, Kazuya ; Ito, Akihiko - \ 2016
Annals of Botany 118 (2016)2. - ISSN 0305-7364 - p. 239 - 247.
Canopy photosynthesis - functional group - leaf area index - light distribution - light extinction coefficient - model - nitrogen allocation - nitrogen use - optimization

Background and aims Leaf nitrogen distribution in the plant canopy is an important determinant for canopy photosynthesis. Although the gradient of leaf nitrogen is formed along light gradients in the canopy, its quantitative variations among species and environmental responses remain unknown. Here, we conducted a global meta-analysis of leaf nitrogen distribution in plant canopies. Methods We collected data on the nitrogen distribution and environmental variables from 393 plant canopies (100, 241 and 52 canopies for wheat, other herbaceous and woody species, respectively). Key Results The trends were clearly different between wheat and other species; the photosynthetic nitrogen distribution coefficient (Kb) was mainly determined by leaf area index (LAI) in wheat, whereas it was correlated with the light extinction coefficient (KL) and LAI in other species. Some other variables were also found to influence Kb. We present the best equations for Kb as a function of environmental variables and canopy characteristics. As a more simple function, Kb = 0·5KL can be used for canopies of species other than wheat. Sensitivity analyses using a terrestrial carbon flux model showed that gross primary production tended to be more sensitive to the Kb value especially when nitrogen content of the uppermost leaf was fixed. Conclusion Our results reveal that nitrogen distribution is mainly driven by the vertical light gradient but other factors such as LAI also have significant effects. Our equations contribute to an improvement in the projection of plant productivity and cycling of carbon and nitrogen in terrestrial ecosystems.

Resource use efficiency, ecological intensification and sustainability of intercropping systems
Mao, L. ; Zhang, L. ; Zhang, S. ; Evers, J.B. ; Werf, W. van der; Wang, J. ; Sun, H. ; Su, Z. ; Spiertz, J.H.J. - \ 2015
Journal of Integrative Agriculture 14 (2015)8. - ISSN 2095-3119 - p. 1542 - 1550.
growth - maize - yield - wheat - water - agriculture - radiation - capture - cotton - model
The rapidly growing demand for food, feed and fuel requires further improvements of land and water management, crop productivity and resource-use efficiencies. Combined field experimentation and crop growth modelling during the past five decades made a great leap forward in the understanding of factors that determine actual and potential yields of monocrops. The research field of production ecology developed concepts to integrate biological and biophysical processes with the aim to explore crop growth potential in contrasting environments. To understand the potential of more complex systems (multi-cropping and intercropping) we need an agro-ecosystem approach that integrates knowledge derived from various disciplines: agronomy, crop physiology, crop ecology, and environmental sciences (soil, water and climate). Adaptation of cropping systems to climate change and a better tolerance to biotic and abiotic stresses by genetic improvement and by managing diverse cropping systems in a sustainable way will be of key importance in food security. To accelerate sustainable intensification of agricultural production, it is required to develop intercropping systems that are highly productive and stable under conditions with abiotic constraints (water, nutrients and weather). Strategies to achieve sustainable intensification include developing tools to evaluate crop growth potential under more extreme climatic conditions and introducing new crops and cropping systems that are more productive and robust under conditions with abiotic stress. This paper presents some examples of sustainable intensification management of intercropping systems that proved to be tolerant to extreme climate conditions.
The relationship between leaf area growth and biomass accumulation in Arabidopsis thaliana
Weraduwage, S.M. ; Chen, J. ; Anozie, F.C. ; Morales Sierra, A. ; Weise, S.E. ; Sharkey, T.D. - \ 2015
Frontiers in Plant Science 6 (2015). - ISSN 1664-462X - 21 p.
plant-growth - photosynthetic acclimation - nighttime transpiration - phaseolus-vulgaris - starch turnover - root-growth - model - respiration - light - maintenance
Leaf area growth determines the light interception capacity of a crop and is often used as a surrogate for plant growth in high-throughput phenotyping systems. The relationship between leaf area growth and growth in terms of mass will depend on how carbon is partitioned among new leaf area, leaf mass, root mass, reproduction, and respiration. A model of leaf area growth in terms of photosynthetic rate and carbon partitioning to different plant organs was developed and tested with Arabidopsis thaliana L. Heynh. ecotype Columbia (Col-0) and a mutant line, gigantea-2 (gi-2), which develops very large rosettes. Data obtained from growth analysis and gas exchange measurements was used to train a genetic programming algorithm to parameterize and test the above model. The relationship between leaf area and plant biomass was found to be non-linear and variable depending on carbon partitioning. The model output was sensitive to the rate of photosynthesis but more sensitive to the amount of carbon partitioned to growing thicker leaves. The large rosette size of gi-2 relative to that of Col-0 resulted from relatively small differences in partitioning to new leaf area vs. leaf thickness.
Partitioned EDGE devices for high throughput production of monodisperse emulsion droplets with two distinct sizes
Sahin, S. ; Schroën, C.G.P.H. - \ 2015
Lab on a Chip 15 (2015). - ISSN 1473-0197 - p. 2486 - 2495.
flow membrane emulsification - microchannel emulsification - generation - dynamics - model - geometries - parallel
We present a novel microfluidic EDGE (Edge based Droplet GEneration) device with regularly spaced micron-sized partitions, which is aimed at upscaling of o/w emulsion preparation. By this means, remarkably higher pressure stability was obtained, and two orders of magnitude higher droplet formation frequency was achieved compared to regular EDGE devices. Interestingly, we observed two different monodisperse droplet formation regimes for plateaus that were 2 micrometres in height, and to the best of our knowledge, no other microfluidic device has this ability. The average diameters of the droplets were 9 and 28 µm, both with a coefficient of variation (CV) below 5%. Based on the experimental throughput and a plausible mass parallelization scenario, the amount of hexadecane that can be emulsified is estimated to be between 6 and 25 m3 m-2 h-1 depending on the required droplet size. With its high throughput potential and ability to produce uniform droplets of two different sizes, the partitioned EDGE device is promising for industrial emulsion production.
Simulation of the phenological development of wheat and maize at the global scale
Bussel, L.G.J. van; Stehfest, E. ; Siebert, S. ; Müller, C. ; Ewert, F. - \ 2015
Global Ecology and Biogeography 24 (2015)9. - ISSN 1466-822X - p. 1018 - 1029.
climate-change - winter-wheat - annual crops - photoperiod sensitivity - geographical variation - temperature - responses - adaptation - cultivars - model
To derive location-specific parameters that reflect the geographic differences among cultivars in vernalization requirements, sensitivity to day length (photoperiod) and temperature, which can be used to simulate the phenological development of wheat and maize at the global scale. Location: Global. Methods: Based on crop calendar observations and literature describing the large-scale patterns of phenological characteristics of cultivars, we developed algorithms to compute location-specific parameters to represent this large-scale pattern. Vernalization requirements were related to the duration and coldness of winter, sensitivity to day length was assumed to be represented by the minimum and maximum day lengths occurring at a location, and sensitivity to temperature was related to temperature conditions during the vegetative development phase of the crop. Results: Application of the derived location-specific parameters resulted in high agreement between simulated and observed lengths of the cropping period. Agreement was especially high for wheat, with mean absolute errors of less than 3 weeks. In the main maize cropping regions, cropping periods were over- and underestimated by 0.5-1.5 months. We also found that interannual variability in simulated wheat harvest dates was more realistic when accounting for photoperiod effects. Main conclusions: The methodology presented here provides a good basis for modelling the phenological characteristics of cultivars at the global scale. We show that current global patterns of growing season length as described in cropping calendars can be largely reproduced by phenology models if location-specific parameters are derived from temperature and day length indicators. Growing seasons can be modelled more accurately for wheat than for maize, especially in warm regions. Our method for computing parameters for phenology models from temperature and day length offers opportunities to improve the simulation of crop productivity by crop simulation models developed for large spatial areas and for long-term climate impact projections that account for adaptation in the selection of varieties.
Street greenery and its physical and psychological impact on outdoor thermal comfort
Klemm, W. ; Heusinkveld, B.G. ; Lenzholzer, S. ; Hove, B. van - \ 2015
Landscape and Urban Planning 138 (2015). - ISSN 0169-2046 - p. 87 - 98.
urban-environment - climate-change - human health - vegetation - spaces - infrastructure - design - model - landscapes - trees
This study focuses on the benefits of street greenery for creating thermally comfortable streetscapes in moderate climates. It reports on investigations on the impact of street greenery on outdoor thermal comfort from a physical and psychological perspective. For this purpose, we examined nine streets with comparable geometric configurations, but varying amount of street greenery (street trees, front gardens) in the city of Utrecht, the Netherlands. Mobile micrometeorological measurements including air temperature (Ta), solar and thermal radiation were performed, enabling the calculation of mean radiant temperature (Tmrt). Additionally, semi-structured interviews with pedestrians about their momentary and long-term perceived thermal comfort and their esthetical appreciation of the green street design were conducted. Measurements showed a clear impact (p = 0.0001) of street greenery on thermal comfort through tree shading: 10% tree crown cover within a street canyon lowered street averaged Tmrt about 1 K. In contrast, our results did not show an influence of street greenery on street averaged Ta. Interview results indicated that momentary perceived thermal comfort tended to be related to the amount of street greenery. However, the results were not statistically significant. Related to long-term perceived thermal comfort respondents were hardly consciously aware of influences by street greenery. Yet, people significantly (p <0.001) valued the presence of street greenery in esthetic terms. In conclusion, street greenery forms a convenient adaptive strategy to create thermally comfortable and attractive living environments. Our results clearly indicate that both physical and psychological aspects of thermal comfort have to be considered in urban design processes.
Thermal comfort of outdoor spaces in Lahore Pakistan: Lessons for bioclimatic urban design in the context of global climate change
Mazhar, N. ; Brown, R.D. ; Kenny, N. ; Lenzholzer, S. - \ 2015
Landscape and Urban Planning 138 (2015). - ISSN 0169-2046 - p. 110 - 117.
heat-stress - model
Humans interact with urban microclimates through exchanges of energy. A surplus of energy can create thermal discomfort and be detrimental to human health. Many cities in warm regions all over the world are forecast to become very hot through global climate change. Some cities already experience extreme heat and have done so for centuries. We conducted a study of one such city in order to generate design guidelines for creating thermally comfortable outdoor places. In the hot, dry city of Lahore, Pakistan we compared the microclimates of two very different outdoor spaces. The first place was the 16th century Shalimar Garden, which contains much green infrastructure and water features. The other example was the hard-surfaced courtyard of the contemporary Alhamra Art Centre. In both places we measured the microclimatic characteristics and used those data to simulate thermal sensation through the energybudget model COMFA. The measured air temperature and humidity in both spaces was similar. However, the solar radiation that would be received by a person in the Alhamra courtyard was much higher than in Shalimar Garden and was the main determinant of thermal discomfort. Results from this study can inform other cities in hot, dry climates about design responses that provide more outdoor thermal comfort and prevent health-threatening heat. (C) 2015 Elsevier B.V. All rights reserved.
Accurate assessment of the biodegradation of cationic surfactants in activated sludge reactors (OECD TG 303A)
Geerts, R. ; Ginkel, C.G. van; Plugge, C.M. - \ 2015
Ecotoxicology and Environmental Safety 118 (2015). - ISSN 0147-6513 - p. 83 - 89.
sewage-treatment - treatment-plant - ammonium-salts - fate - model - chemicals
The continuous-fed activated sludge test (OECD TG 303A) was used to predict the removal of cationic surfactants from wastewater in activated sludge plants. However, a method to differentiate between adsorption and biodegradation is not provided in these guidelines. Assessment of removal by biodegradation was possible with analysis of the surfactant present in mixed liquid suspended solids in combination with a simple equation. This equation was derived from the mass balance of the activated sludge unit in steady state. The removal by biodegradation of decylamine, tetradecylamine, octadecylamine, dioctadecylmethylamine and dioctadecyldimethylammonium chloride that have different capacities to adsorb was >99.9%, >99.9%, 98.2%, 94.2%, and 69.0%, respectively. The total removal of all five cationic surfactants from the influent was =98.8%. The removal of octadecylamine spiked at different influent concentrations indicated first order kinetics
Effect of feed-related farm characteristics on relative values of genetic traits in dairy cows to reduce greenhouse gas emissions along the chain
Middelaar, C.E. van; Berentsen, P.B.M. ; Dijkstra, J. ; Arendonk, J.A.M. van; Boer, I.J.M. de - \ 2015
Journal of Dairy Science 98 (2015)7. - ISSN 0022-0302 - p. 4889 - 4903.
life-cycle assessment - genomic selection - economic values - milk-production - methane - cattle - mitigation - impact - level - model
Breeding has the potential to reduce greenhouse gas (GHG) emissions from dairy farming. Evaluating the effect of a 1-unit change (i.e., 1 genetic standard deviation improvement) in genetic traits on GHG emissions along the chain provides insight into the relative importance of genetic traits to reduce GHG emissions. Relative GHG values of genetic traits, however, might depend on feed-related farm characteristics. The objective of this study was to evaluate the effect of feed-related farm characteristics on GHG values by comparing the values of milk yield and longevity for an efficient farm and a less efficient farm. The less efficient farm did not apply precision feeding and had lower feed production per hectare than the efficient farm. Greenhouse gas values of milk yield and longevity were calculated by using a whole-farm model and 2 different optimization methods. Method 1 optimized farm management before and after a change in genetic trait by maximizing labor income; the effect on GHG emissions (i.e., from production of farm inputs up to the farm gate) was considered a side effect. Method 2 optimized farm management after a change in genetic trait by minimizing GHG emissions per kilogram of milk while maintaining labor income and milk production at least at the level before the change in trait; the effect on labor income was considered a side effect. Based on maximizing labor income (method 1), GHG values of milk yield and longevity were, respectively, 279 and 143 kg of CO2 equivalents (CO2e)/unit change per cow per year on the less efficient farm, and 247 and 210 kg of CO2e/unit change per cow per year on the efficient farm. Based on minimizing GHG emissions (method 2), GHG values of milk yield and longevity were, respectively, 538 and 563 kg of CO2e/unit change per cow per year on the less efficient farm, and 453 and 441 kg of CO2e/unit change per cow per year on the efficient farm. Sensitivity analysis showed that, for both methods, the absolute effect of a change in genetic trait depends on model inputs, including prices and emission factors. Substantial changes in relative importance between traits due to a change in model inputs occurred only in case of maximizing labor income. We concluded that assumptions regarding feed-related farm characteristics affect the absolute level of GHG values, as well as the relative importance of traits to reduce emissions when using a method based on maximizing labor income. This is because optimizing farm management based on maximizing labor income does not give any incentive for lowering GHG emissions. When using a method based on minimizing GHG emissions, feedrelated farm characteristics affected the absolute level of the GHG values, but the relative importance of the traits scarcely changed: at each level of efficiency, milk yield and longevity were equally important. Key words: breeding, milk yield, longevity, economic value.
Microfluidic emulsification in food processing
Maan, A.A. ; Nazir, A. ; Khan, M.K.I. ; Boom, R.M. ; Schroën, C.G.P.H. - \ 2015
Journal of Food Engineering 147 (2015). - ISSN 0260-8774 - p. 1 - 7.
through microchannel emulsification - monodisperse emulsion droplets - flow-focusing geometries - t-shaped microchannel - membrane emulsification - interfacial-tension - y-junctions - water - devices - model
Microfluidic systems, characterized by micro-meter sized channels, are used in a variety of applications. In foods, the most common application is in the preparation of emulsions where they provide accurate control over droplet size, and shape of internal structures. This paper gives an overview of different microfluidic emulsification techniques ie, shear driven and spontaneous droplet generation, together with their current limitations. Next a comparison is made on the basis of various parameters affecting the process of ...
ERP in agriculture: Lessons learned from the Dutch horticulture
Verdouw, C.N. ; Robbemond, R.M. ; Wolfert, J. - \ 2015
Computers and Electronics in Agriculture 114 (2015). - ISSN 0168-1699 - p. 125 - 133.
critical success factors - enterprise systems - future internet - supply chains - management - impact - model - perspective - innovation - adoption
Farming nowadays is a complex managerial task that imposes stringent requirements on farm management information systems. In other sectors, Enterprise Resource Planning (ERP) systems are widely implemented to meet such requirements. This paper assesses the applicability of ERP systems in the agri-food domain by investigating the experiences of agri-food companies that already have implemented an ERP system. More specifically, the research has analyzed the drivers and barriers for adoption of ERP in the Dutch horticultural sector. The results show that the alignment of ERP with the specific characteristics and requirements of a company is a crucial challenge in order to capitalize the benefits of ERP. The study also shows that it is possible to deal with this challenge. The majority of the respondents (62%) is positive about of the match of the specific ERP solution with the company’s business processes during implementation. Most of these respondents have implemented a system that includes a sector-specific layer around a standard ERP solution. Moreover, it is concluded that a proper management of the orientation, selection and implementation processes is of crucial importance for a successful adoption.
Causal feedbacks in climate change
Nes, E.H. van; Scheffer, M. ; Brovkin, V. ; Lenton, T.M. ; Ye, H. ; Deyle, E. ; Sugihara, G. - \ 2015
Nature Climate Change 5 (2015). - ISSN 1758-678X - p. 445 - 448.
carbon-cycle - ice core - antarctic temperature - last deglaciation - atmospheric co2 - global climate - dioxide - record - model - lag
The statistical association between temperature and greenhouse gases over glacial cycles is well documented1, but causality behind this correlation remains difficult to extract directly from the data. A time lag of CO2 behind Antarctic temperature—originally thought to hint at a driving role for temperature2, 3—is absent4, 5 at the last deglaciation, but recently confirmed at the last ice age inception6 and the end of the earlier termination II (ref. 7). We show that such variable time lags are typical for complex nonlinear systems such as the climate, prohibiting straightforward use of correlation lags to infer causation. However, an insight from dynamical systems theory8 now allows us to circumvent the classical challenges of unravelling causation from multivariate time series. We build on this insight to demonstrate directly from ice-core data that, over glacial–interglacial timescales, climate dynamics are largely driven by internal Earth system mechanisms, including a marked positive feedback effect from temperature variability on greenhouse-gas concentrations.
The contribution of phenotypic plasticity to complementary light capture in plant mixtures
Zhu, J. ; Werf, W. van der; Anten, N.P.R. ; Vos, J. ; Evers, J.B. - \ 2015
New Phytologist 207 (2015)4. - ISSN 0028-646X - p. 1213 - 1222.
functional diversity - current knowledge - biodiversity - productivity - photosynthesis - competition - model - communities - variability - environment
Interspecific differences in functional traits are a key factor for explaining the positive diversity– productivity relationship in plant communities. However, the role of intraspecific variation attributable to phenotypic plasticity in diversity–productivity relationships has largely been overlooked. By taking a wheat (Triticum aestivum)–maize (Zea mays) intercrop as an elementary example of mixed vegetation, we show that plasticity in plant traits is an important factor contributing to complementary light capture in species mixtures. We conceptually separated net biodiversity effect into the effect attributable to interspecific trait differences and species distribution (community structure effect), and the effect attributable to phenotypic plasticity. Using a novel plant architectural modelling approach, whole vegetation light capture was simulated for scenarios with and without plasticity based on empirical plant trait data. Light capture was 23% higher in the intercrop with plasticity than the expected value from monocultures, of which 36% was attributable to community structure and 64% was attributable to plasticity. For wheat, plasticity in tillering was the main reason for increased light capture, whereas for intercropped maize, plasticity induced a major reduction in light capture. The results illustrate the potential of plasticity for enhancing resource acquisition in mixed stands, and indicate the importance of plasticity in the performance of species-diverse plant communities.
How good is good enough? Data requirements for reliable crop yield simulations and yield-gap analysis
Grassini, P. ; Bussel, L.G.J. van; Wart, J. van; Wolf, J. ; Claessens, L. ; Yang, H. ; Boogaard, H.L. ; Groot, H.L.E. de; Ittersum, M.K. van; Cassman, K.G. - \ 2015
Field Crops Research 177 (2015). - ISSN 0378-4290 - p. 49 - 63.
pedo-transfer functions - daily solar-radiation - water-use efficiency - climate-change - distribution maps - weather data - corn-belt - maize - model - impact
Numerous studies have been published during the past two decades that use simulation models to assesscrop yield gaps (quantified as the difference between potential and actual farm yields), impact of climatechange on future crop yields, and land-use change. However, there is a wide range in quality and spatialand temporal scale and resolution of climate and soil data underpinning these studies, as well as widelydiffering assumptions about cropping-system context and crop model calibration. Here we present anexplicit rationale and methodology for selecting data sources for simulating crop yields and estimatingyield gaps at specific locations that can be applied across widely different levels of data availability andquality. The method consists of a tiered approach that identifies the most scientifically robust require-ments for data availability and quality, as well as other, less rigorous options when data are not availableor are of poor quality. Examples are given using this approach to estimate maize yield gaps in the stateof Nebraska (USA), and at a national scale for Argentina and Kenya. These examples were selected torepresent contrasting scenarios of data availability and quality for the variables used to estimate yieldgaps. The goal of the proposed methods is to provide transparent, reproducible, and scientifically robustguidelines for estimating yield gaps; guidelines which are also relevant for simulating the impact of cli-mate change and land-use change at local to global spatial scales. Likewise, the improved understandingof data requirements and alternatives for simulating crop yields and estimating yield gaps as describedhere can help identify the most critical “data gaps” and focus global efforts to fill them. A related paper(Van Bussel et al., 2015) examines issues of site selection to minimize data requirements and up-scalingfrom location-specific estimates to regional and national spatial scales.
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.
Establishing Guidelines to Retain Viability of Probiotics during Spray Drying
Perdana, J.A. ; Fox, M.B. ; Boom, R.M. ; Schutyser, M.A.I. - \ 2015
Drying Technology 33 (2015)13. - ISSN 0737-3937 - p. 1560 - 1569.
lactobacillus-plantarum wcfs1 - inactivation - integration - isotherms - products - sorption - storage - trends - foods - model
We present the application of a model-based approach to map processing conditions suitable to spray dry probiotics with minimal viability loss. The approach combines the drying history and bacterial inactivation kinetics to predict the retention of viability after drying. The approach was used to systematically assess the influence of operational co-current spray drying conditions on residual viability. Moreover, two promising alternative drying strategies for probiotics were evaluated involving encapsulation in a hollow particle and using an ‘ideal-mixed’ dryer system. Finally, a graph was constructed with the model to provide visual guidelines to optimize spray dying for probiotics in terms of viability and drying efficiency.
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