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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Research idea to science for impact : Tracing the significant moments in an innovation based irrigation study
Srinivasan, M.S. ; Jongmans, C. ; Bewsell, D. ; Elley, G. - \ 2019
Agricultural Water Management 212 (2019). - ISSN 0378-3774 - p. 181 - 192.
Co-innovation - Co-learning - Irrigation - Stakeholder management - Weather forecast

Uptake of irrigation scheduling tools by New Zealand (NZ) farmers has remained static for many years and some researchers consider the use of linear, tech-transfer approaches as the main reason for this. To understand the controls and drivers that influence the uptake of these tools and to evaluate the effectiveness of a co-innovation approach in improving their (tools) uptake, a team of biophysical (hydrologists) and social researchers undertook a pilot study in an irrigation scheme in the South Island of NZ. Co-innovation offers a multi-directional, multi-level, multi-actor approach, in which input from stakeholders is valued in every part of the process, from problem definition to solution adoption. In this study, we focused on the adaptive aspect of co-innovation that allows stakeholders to periodically review their actions and respond to it in a way that is inclusive others’ views and reflective of feedback received. The pilot study activities were analysed retrospectively to develop a systemic view to the implementation of a co-innovation-based multi-stakeholder hydrology project. While implementing a co-innovation approach, five chronologically-distinct yet overlapping phases emerged in the project: 1. concept development, where the hydrologists came up with the research idea and seed concept; 2. trust building, where researchers (hydrologists and social) interacted with key on-farm stakeholders in developing and implementing the research idea into a pilot field study; 3. knowledge synthesis, where researchers collected on-farm biophysical and behavioural data to record practice change; 4. extended outreach, where stakeholders, including researchers, devised pathways to sustain the lessons learned and practices changed, and disseminated the learnings to the wider irrigation community; and 5. project legacy, where the researchers, after the development of the seed concept into a practice change, evolved an exit strategy. Apart from core research activities, such as data collection on irrigation water use and changes in irrigation scheduling practices, each one of the five phases included actions that were unique to that phase as well as to achieving the wider pilot study goal of improving water use efficiency. This paper discusses the learnings from these phases, including insights, and key identifiers and indicators of pilot study progression during each phase, which may serve as an example to other biophysical studies that propose to employ co-innovation-based multi stakeholder approach.

Predicting soil microplastic concentration using vis-NIR spectroscopy
Corradini, Fabio ; Bartholomeus, Harm ; Huerta Lwanga, Esperanza ; Gertsen, Hennie ; Geissen, Violette - \ 2019
Science of the Total Environment 650 (2019). - ISSN 0048-9697 - p. 922 - 932.
Microplastics - Near-infrared spectroscopy - Soil pollution - Spectroradiometer - Vis-NIR

Microplastic accumulation in soil may have a detrimental impact on soil biota. The lack of standardized methods to identify and quantify microplastics in soils is an obstacle to research. Existing techniques are time-consuming and field data are seldom collected. To tackle the problem, we explored the possibilities of using a portable spectroradiometer working in the near infrared range (350–2500 nm) to rapidly assess microplastic concentrations in soils without extraction. Four sets of artificially polluted soil samples were prepared. Three sets had only one polymer polluting the soil (low-density polyethylene (LDPE), polyethylene terephthalate (PET), or polyvinyl chloride (PVC)). The fourth set contained random amounts of the three polymers (Mix). The concentrations of microplastics were regressed on the reflectance observed for each of the 2150 wavelengths registered by the instrument, using a Bayesian approach. For a measurement range between 1 and 100 g kg−1, results showed a root-mean-squared-deviation (RMSD) of 8, 18, and 10 g kg−1 for LDPE, PET, and PVC. The Mix treatment presented an RMSD of 8, 10, and 5 g kg−1 for LDPE, PET, and PVC. The repeatability of the proposed method was 0.2–8.4, 0.1–5.1, and 0.1–9.0 g kg−1 for LDPE, PET, and PVC, respectively. Overall, our results suggest that vis-NIR techniques are suitable to identify and quantify LDPE, PET, and PVC microplastics in soil samples, with a 10 g kg−1 accuracy and a detection limit ≈ 15 g kg−1. The method proposed is different than other approaches since it is faster because it avoids extraction steps and can directly quantify the amount of plastic in a sample. Nevertheless, it seems to be useful only for pollution hotspots.

Plastic film cover during the fallow season preceding sowing increases yield and water use efficiency of rain-fed spring maize in a semi-arid climate
Zhang, Zhe ; Zhang, Yanqing ; Sun, Zhanxiang ; Zheng, Jiaming ; Liu, Enke ; Feng, Liangshan ; Feng, Chen ; Si, Pengfei ; Bai, Wei ; Cai, Qian ; Yang, Ning ; Werf, Wopke van der; Zhang, Lizhen - \ 2019
Agricultural Water Management 212 (2019). - ISSN 0378-3774 - p. 203 - 210.
Film cover - Soil temperature - Water availability - Yield components

Plastic film mulch increases crop yields in rain-fed agriculture in cool semi-arid climates by warming the soil and reducing evaporative water losses. The semi-arid Khorchin area in Northeast China is an important production area for rain-fed maize. Drought stress occurs frequently, even if plastic film mulch is applied at sowing. We hypothesized that the yield and water capture of maize could be increased by reducing evaporative loss of water by use of plastic film cover during the autumn and winter preceding sowing. In this study, we compared maize growth, water uptake and yield in three film cover treatments: (1) film cover from the autumn before maize sowing until maize harvest (autumn mulching: AM), (2) film cover from maize sowing till harvest (conventional practice) (spring mulching: SM), (3) no film cover (no mulch: NM). Field experiments were conducted in Fuxin city, Khorchin region, Liaoning province, China in 2013/2014 and 2014/2015. Autumn mulching increased grain yield on average by 18% when compared to spring mulching and by 36% when compared to no mulching. The 1000-kernel weight in AM was 7% higher than in SM, and 12% higher than in NM. Soil water content in the root zone before sowing was 35 mm greater in AM than in SM and NM. Water uptake during the growing season was 34 mm greater in AM than in SM and NM. Water use efficiency for grain yield (yield per unit water uptake) in AM was on average 2.5% higher than in conventional mulching (SM) and 27% higher than in NM. Autumn mulching advanced development, with an advance of 5 days in tasseling time as compared to SM and 10 days when compared to NM. These results show that film cover during the fallow period before maize sowing can increase crop yield and water use efficiency, and reduce climate risks in rain-fed agriculture under semi-arid conditions.

Irrigation reduces the negative effect of global warming on winter wheat yield and greenhouse gas intensity
Li, Jiazhen ; Dong, Wenxu ; Oenema, Oene ; Chen, Tuo ; Hu, Chunsheng ; Yuan, Haijing ; Zhao, Liying - \ 2019
Science of the Total Environment 646 (2019). - ISSN 0048-9697 - p. 290 - 299.
Global warming potential - Greenhouse gas intensity - Greenhouse gases - Irrigation - Warming - Wheat yield

Global warming may exacerbate drought, decrease crop yield and affect greenhouse gas (GHG) emissions in semi-arid regions. However, the interactive effects of increases in temperature and water availability on winter wheat yield and GHG emissions in semi-arid climates are not well-understood. Here, we report on a two-year field experiment that examined the effects of a mean soil temperature increase of ~2 °C (at 5 cm depth) with and without additional irrigation on wheat yield and GHG emissions. Infrared heaters were placed above the crop canopy at a height of 1.8 m to simulate warming. Fluxes of CH4, CO2 and N2O were measured using closed static chamber technique once per week during the wheat growing seasons. Warming decreased wheat yield by 28% in the relatively dry year of 2015, while supplemental irrigation nullified the warming effect completely. Warming did not alter the wheat yield significantly in the relatively wet year of 2016, but supplemental irrigation with no warming decreased the wheat yield by 25%. Warming increased CO2 emissions by 28% and CH4 uptake by 24% and tended to decrease N2O emissions. Supplemental irrigation increased N2O emissions but had little effect on CO2 emissions and CH4 uptake. Evidently, warming and supplemental irrigation had interactive effects on wheat yield, GHG emissions and GHG emissions intensity. Precision irrigation appears to be a means of simultaneously increasing wheat yield and reducing GHG emissions under warming conditions in semi-arid areas.

Heterogeneity of Network Structures and Water Dynamics in κ‑Carrageenan Gels Probed by Nanoparticle Diffusometry
Kort, D.W. de; Schuster, Erich ; Hoeben, F.J.M. ; Barnes, R. ; Emondts, Meike ; Janssen, Henk M. ; Lorén, Niklas ; Han, Songi ; As, H. Van; Duynhoven, J.P.M. van - \ 2018
Langmuir 34 (2018). - ISSN 0743-7463 - p. 11110 - 11120.
A set of functionalized nanoparticles (PEGylated dendrimers, d = 2.8−11 nm) was used to probe the structural heterogeneity in Na+/K+ induced κ-carrageenan gels. The self-diffusion behavior of these nanoparticles as observed by 1H pulsed-field gradient NMR, fluorescence recovery after photobleaching, and raster image correlation spectroscopy revealed a fast and a slow component, pointing toward microstructural heterogeneity in the gel network. The self-diffusion behavior of the faster nanoparticles could be modeled with obstruction by a coarse network (average mesh size <100 nm), while the slower-diffusing nanoparticles are trapped in a dense network (lower mesh size limit of 4.6 nm). Overhauser dynamic nuclear polarization-enhanced NMR relaxometry revealed a reduced local solvent water diffusivity near 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-labeled nanoparticles trapped in the dense network, showing that heterogeneity in the physical network is also reflected in heterogeneous self-diffusivity of water. The observed heterogeneity in mesh sizes and in water self-diffusivity is of interest for understanding and modeling of transport through and release of solutes from heterogeneous biopolymer gels.
Chimeric O1K foot-and-mouth disease virus with SAT2 outer capsid as an FMD vaccine candidate
Kotecha, Abhay ; Perez-Martin, Eva ; Harvey, Yongjie ; Zhang, Fuquan ; Ilca, Serban L. ; Fry, Elizabeth E. ; Jackson, Ben ; Maree, Francois ; Scott, Katherine ; Hecksel, Corey W. ; Harmsen, Michiel M. ; Mioulet, Valérie ; Wood, Britta ; Juleff, Nick ; Stuart, David I. ; Charleston, Bryan ; Seago, Julian - \ 2018
Scientific Reports 8 (2018)1. - ISSN 2045-2322

Foot-and-mouth disease virus (FMDV) is highly contagious and infects cloven-hoofed domestic livestock leading to foot-and-mouth disease (FMD). FMD outbreaks have severe economic impact due to production losses and associated control measures. FMDV is found as seven distinct serotypes, but there are numerous subtypes within each serotype, and effective vaccines must match the subtypes circulating in the field. In addition, the O and Southern African Territories (SAT) serotypes, are relatively more thermolabile and their viral capsids readily dissociate into non-immunogenic pentameric subunits, which can compromise the effectiveness of FMD vaccines. Here we report the construction of a chimeric clone between the SAT2 and O serotypes, designed to have SAT2 antigenicity. Characterisation of the chimeric virus showed growth kinetics equal to that of the wild type SAT2 virus with better thermostability, attributable to changes in the VP4 structural protein. Sequence and structural analyses confirmed that no changes from SAT2 were present elsewhere in the capsid as a consequence of the VP4 changes. Following exposure to an elevated temperature the thermostable SAT2-O1K chimera induced higher neutralizing-antibody titres in comparison to wild type SAT2 virus.

Advanced classification of volunteer potato in a sugar beet field
Suh, Hyun K. - \ 2018
University. Promotor(en): Eldert van Henten, co-promotor(en): Jan Willem Hofstee; Joris IJsselmuiden. - Wageningen : Wageningen University - ISBN 9789463437912 - 190
Structuring processes for meat analogues
Dekkers, Birgit L. ; Boom, Remko M. ; Goot, Atze Jan van der - \ 2018
Trends in Food Science and Technology 81 (2018). - ISSN 0924-2244 - p. 25 - 36.
Anisotropy - Fibrous products - Meat analogues - Plant protein - Structuring

Background: Animal-derived protein foods, such as meat, have a large impact on the environment. Meat analogues are products that replace meat in its functionality, i.e. have similar product properties and sensory attributes, which is achieved by the fibrous nature of those products. Scope and approach: The techniques used to make fibrous products that mimic muscle meats are outlined and categorized based on their approach. The bottom-up approach refers to assembly of structural elements that are combined. The top-down approach refers to structuring of biopolymer blends using an overall force field. The strengths and weaknesses of these approaches are discussed in terms of ingredient and equipment use, (achievable) product resemblance, robustness, scalability, and resource efficiency. To enlarge the theoretical framework, the techniques with the top-down strategy are further contextualized by relating to structure formation processes of materials with other applications, and the methods to analyse the fibrous structures are further outlined. Key findings and conclusions: Techniques that follow the bottom-up strategy have the potential to resemble the structure of meat most closely, by structuring the proteins hierarchically through assembly of individual structural components. The top-down strategy is better scalable, is more efficient in its use of resources, but can only create the desired structure on larger length scales. Significant progress has been made on the methods to analyse structured products from the last category. Most analysis methods focussed on the (micro)structural anisotropy of the fibrous products, however there is also a need for methods that allow in situ analysis of the evolution of the structure during processing.

Risk management options in maize cropping systems in semi-arid areas of Southern Africa
Masvaya, Esther N. ; Nyamangara, Justice ; Giller, Ken E. ; Descheemaeker, Katrien - \ 2018
Field Crops Research 228 (2018). - ISSN 0378-4290 - p. 110 - 121.
Grain requirement - N mineralisation - N stress - Runoff curve number - Water stress

Although rainfed cropping in semi-arid areas is risky due to frequent droughts and dry spells, planting early with the first rains is often expected to result in yield benefits. We hypothesised that planting early leads to yield benefits if the planting coincides with a mineral N flush at the start of the season but leads to crop failure if there is a false start to the cropping season. The effects of different management options, including tillage (ploughing and ripping), mulch (two levels 0 and 2 t ha−1) and fertility amendments (five levels: 0; 20 and 40 kg N ha−1; 5 t manure ha−1 and 5 t ha−1 manure + 20 kg N ha−1) on grain yields were simulated using the calibrated and tested APSIM model over a 30-year period (1984–2015). Yields were simulated and compared across seven planting date scenarios (1 November, 15 November, 30 November, 15 December, 31 December, 15 January and planting when cumulative rainfall of 20 mm was received in three consecutive days). Planting with the first rains with manure + 20 kg N ha−1 resulted in the best average yield of 2271 kg ha−1 whilst the poorest average yields of 22 kg ha−1 were observed with planting on 15 January with no fertility amendment (0 kg N ha−1). Planting early (1 Nov to 15 Nov) and with the first rains resulted in exceeding the food self-sufficiency threshold of 1080 kg ha-1 in 40–83 % of the cases if fertility amendments are applied, as well as a low probability of complete crop failure, ranging from 0 to 40%. Grain yield penalties due to a false start followed the trend: ripper + mulch > plough + mulch > ripper (no mulch) averaging 256, 190 and 182 kg ha-1 respectively across all the fertility treatments. The model was able to simulate the occurrence of the mineral N flush with the first rains. Its coincidence with planting resulted in average yield benefits of 712, 452, 382 and 210 kg ha-1 for the following respective planting dates: 1 Nov, 15 Nov, 30 Nov, variable date when >20 mm rainfall was received. Early planting, in combination with reduced tillage, mulch and N containing fertility amendments is critical to reduce risk of crop failure in the smallholder cropping systems of semi-arid areas of southern Africa and achieve the best possible yields.

Local functioning, landscape structuring : Drivers of soil microbial community structure and function in peatlands
Teurlincx, Sven ; Heijboer, Amber ; Veraart, Annelies J. ; Kowalchuk, George A. ; Steven, Steven A. - \ 2018
Frontiers in Microbiology 9 (2018)SEP. - ISSN 1664-302X
Biolog Ecoplates - CLPP - Ditch margins - Landscape ecology - Microbial community - Peatland management - Peatlands - PLFA

Agricultural peatlands are essential for a myriad of ecosystem functions and play an important role in the global carbon (C) cycle through C sequestration. Management of these agricultural peatlands takes place at different spatial scales, ranging from local to landscape management, and drivers of soil microbial community structure and function may be scale-dependent. Effective management for an optimal biogeochemical functioning thus requires knowledge of the drivers on soil microbial community structure and functioning, as well as the spatial scales upon which they are influenced. During two field campaigns, we examined the importance of different drivers (i.e., soil characteristics, nutrient management, vegetation composition) at two spatial scales (local vs. landscape) for, respectively, the soil microbial community structure (determined by PLFA) and soil microbial community functional capacity (as assessed by CLPP) in agricultural peatlands. First, we show by an analysis of PLFA profiles that the total microbial biomass changes with soil moisture and relative C:P nutrient availability. Secondly, we showed that soil communities are controlled by a distinct set of drivers at the local, as opposed to landscape, scale. Community structure was found to be markedly different between areas, in contrast to community function which showed high variability within areas. We further found that microbial structure appears to be controlled more at a landscape scale by nutrient-related variables, whereas microbial functional capacity is driven locally through plant community feedbacks. Optimal management strategies within such peatlands should therefore consider the scale-dependent action of soil microbial community drivers, for example by first optimizing microbial structure at the landscape scale by targeted areal management, and then optimizing soil microbial function by local vegetation management.

Evaluation of three mainstream numerical weather prediction models with observations from meteorological mast IJmuiden at the North Sea
Kalverla, Peter ; Steeneveld, Gert Jan ; Ronda, Reinder ; Holtslag, Albert A.M. - \ 2018
- p. 1 - 15.
Met mast IJmuiden - Model evaluation - North Sea - Numerical weather prediction

Numerical weather prediction models play an important role in the field of wind energy, for example, in power forecasting, resource assessment, wind farm (wake) simulations, and load assessment. Continuous evaluation of their performance is crucial for successful operations and further understanding of meteorology for wind energy purposes. However, extensive offshore observations are rarely available. In this paper, we use unique met mast and Lidar observations up to 315 m from met mast “IJmuiden,” located in the North Sea 85 km off the Dutch coast, to evaluate the representation of wind and other relevant variables in three mainstream meteorological models: ECMWF-IFS, HARMONIE-AROME, and WRF-ARW, for a wide range of weather conditions. Overall performance for hub-height wind speed is found to be comparable between the models, with a systematic wind speed bias <0.5 m/s and random wind speed errors (centered RMSE) <2 m/s. However, the model performance differs considerably between cases, with better performance for strong wind regimes and well-mixed wind and potential temperature profiles. Conditions characterized by moderate wind speeds combined with stable stratification, which typically produce substantial wind shear and power fluctuations, lead to the largest misrepresentations in all models.

Grand challenges in soft matter physics
Gucht, Jasper van der - \ 2018
Active matter - Colloids - Non-equilibrium physics - Polymers - Self-assembly - Soft matter physics

As its name implies, soft matter science deals with materials that are easily deformed. These materials, which include polymers, gels, colloids, emulsions, foams, surfactant assemblies, liquid crystals, granular materials, and many biological materials, have in common that they are organized on mesoscopic length scales, with structural features that are much larger than an atom, but much smaller than the overall size of the material. The large size of the basic structural units and the relatively weak interactions that hold them together are responsible for the characteristic softness of these materials1, but they also lead to many other distinct features of soft materials [1], such as sensitivity toward thermal fluctuations and external stimuli and a slow response with long relaxation times, often resulting in non-trivial flow behavior and arrest in non-equilibrium states. These features make soft matter problems challenging. In hard condensed matter physics, it is often possible to accurately predict material properties based on the interactions between the individual atoms, which are typically organized on a regular crystalline lattice. For soft matter systems, with their intrinsically heterogeneous structure, complex interactions across different length scales, and slow dynamics, this is much more difficult. The subtle interplay between interactions and thermal fluctuations can lead to complex emergent behavior, such as spontaneous pattern formation, self-assembly, and a large response to small external stimuli. Because of the wide range of materials and systems that can be classified as soft matter, soft matter science is an inherently interdisciplinary field, in which physics, chemistry, materials science, biology, nanotechnology, and engineering come together. For a field that is so broad in scope, it is impossible to do justice to the entire range of outstanding problems or even to identify two or three key challenges. For this reason, I will only highlight a small (and highly personal) selection of current challenges in the field. The interdisciplinary nature of the field will be evident from these examples.

New reference genome sequences for genotyping virulence in continental European field populations of cyst nematodes
Holterman, Martijn - \ 2018
Plant-parasitic nematodes form an increasingly important problem in agriculture, causing significant crop losses worldwide. The majority of these losses are caused by a small number of species, such as cyst nematodes (e.g., Globodera rostochiensis, G. pallida and Heterodera schachtii), root-knot nematodes (Meloidogyne spp.) and stem nematodes (Ditylenchus spp.). With a regulatory ban on most nematicidal agrochemicals, the main method of control at the moment is the use of resistant crop cultivars. However, the current spectrum of nematode resistance genes used in major crops is extremely narrow. Prolonged exposure of field populations to a narrow range of resistance genes can result in the appearance of nematode genotypes with modified virulence characteristics. To improve understanding of the genetic mechanisms underlying selection for virulence in cyst nematodes in The Netherlands, we preferred to generate reference genomes from nematode populations with either minimal or well-defined exposure to host plant resistances. For G. pallida, we deliberately chose an old isolate that had not been exposed to potato cultivars harbouring the resistance genes that were most widely used over the past thirty years. For G. rostochiensis, two near isogenic inbred lines were used that differ in their susceptibility towards the H1 resistance gene in potato. PacBio sequencing technology allowed us to generate new reference genomes for G. pallida, two G. rostochiensis lines and H. schachtii. By comparing these reference genomes with re-sequenced field isolates, we can study the effect of continuous exposure of nematode populations to a limited set of resistance genes on virulence characteristics. The newly generated genome sequences consist of significantly fewer and longer contigs than the publicly available ones from the two potato cyst nematode species. An automated procedure was used to create an initial annotation. After a further manual refinement of the annotation with a particular focus on effector families, these genome sequences will serve as a reference for the elucidation of virulence characteristics in cyst nematode populations from The Netherlands and surrounding countries.
Effector GpRpb-1 from Globodera pallida targets E3 ubiquitin ligase complexes to promote nematode infection
Diaz Granados Muñoz, Amalia - \ 2018
Endoparasitic plant-pathogenic nematodes manipulate plant cell morphology and physiology to establish sophisticated feeding structures. Modifications to plant cells are achieved through the activity of nematode secreted effectors. SPRYSECs are a remarkably expanded family of effectors identified initially in potato cyst nematodes. While SPRYSECs have been implicated in suppression of plant immunity, their intrinsic role in nematode virulence remains unexplored. GpRpb-1 is a ‘type’ SPRYSEC from Globodera pallida with virulent and avirulent variants present in field populations of the nematode. Y2H screening of a nematode-infected susceptible potato library yielded interacting candidates for a virulent GpRpb-1 that are involved in post-translational modification in the plant. We have independently confirmed that E3 ubiquitin ligase UPL3 can interact with GpRbp-1 in planta. Transcriptomic profiling of upl3 mutant plants shows that Skp-like and F-box-like E3 ubiquitin ligases are regulated upon nematode infection. Furthermore, upon silencing of the corresponding ligase genes in A. thaliana, we observed significant differences in the amount of developing females present in the roots of nematode-infected plants. The interaction of GpRbp-1 with UPL3 and the transcriptional regulation of other E3 ubiquitin ligases suggest that the intrinsic role of the effector is carried out through manipulation of the plant post-translational modification machinery. Our findings suggest that nematodes are able to use the SPRYSEC family of effectors to control different aspects of the plant cell to establish a feeding site. Therefore, our results may provide further insight into the basis of virulence of nematodes in plants.
Pooling of genital swabs for detection by PCR of Taylorella equigenitalis, the cause of contagious equine metritis
Mawhinney, I. ; Errington, J. ; Stamper, N. ; Torrens, N. ; Engelsma, M.Y. ; Roest, H.I.J. - \ 2018
Equine Veterinary Journal (2018). - ISSN 0425-1644
diagnosis - horse - infection - validation

Background: Sets of genital swabs are routinely taken from horses to screen for the presence of Taylorella equigenitalis, the cause of contagious equine metritis. Typically, two to four different sites are swabbed at a time and tested by culture or PCR. Objectives: This study explored the feasibility of pooling these swabs for a single PCR test per animal instead of testing each swab individually. Study design: In vitro. Methods: PCR signal strengths (Ct values) from 149 historical PCR positive genital swabs, together with historical data on the number of swabs in a set expected to be positive, were used to assess the suitability of pooling for screening horses for T. equigenitalis infection in the population at large. Twenty-four sets of four equine genital swabs were tested. The sets were prepared in the laboratory using one or more swabs positive for T. equigenitalis from naturally infected cases. Positive and negative swabs were selected to reflect a typical range of PCR Ct values expected in field cases of T. equigenitalis infection. These pools were tested by an established PCR to assess the impact and suitability of a PCR test on pooled swabs compared to individual swab testing, by comparing the Ct values. Results: Pooling one positive swab with three negative swabs produced a small drop in Ct value but all pools were still clearly positive. Main limitations: Large numbers of field positive horses are not available, but the proof of concept approach with laboratory prepared pools shows the method is applicable to field cases. Conclusions: It was concluded that pooling of swabs would confer no appreciable drop in the ability to detect a positive animal compared to individual swab testing; pooling is therefore a suitable alternative to individual swab testing with reduced costs. The Summary is available in Spanish – see Supporting Information.

Data from: Variation in home-field advantage and ability in leaf litter decomposition across successional gradients
Veen, Ciska G.F. ; Keiser, Ashley D. ; Putten, W.H. van der; Wardle, David A. - \ 2018
decomposition - functional breadth - succession - soil - plant-litter feedback
1. It is increasingly recognized that interactions between plants and soil (a)biotic conditions can influence local decomposition processes. For example, decomposer communities may become specialized in breaking down litter of plant species that they are associated with, resulting in accelerated decomposition, known as ‘home-field advantage’ (HFA). Also, soils can vary inherently in their capacity to degrade organic compounds, known as ‘ability’. However, we have a poor understanding how environmental conditions drive the occurrence of HFA and ability. 2. Here, we studied how HFA and ability change across three types of successional gradients: coastal sand dunes (primary succession), inland drift sands (primary succession), and ex-arable fields (secondary succession). Across these gradients, litter quality (i.e., nutrient, carbon and lignin contents) increases with successional time for coastal dunes and decreases for the other two gradients. 3. We performed a 12-month reciprocal litter transplant experiment under greenhouse conditions using soils and litters collected from early-, mid-, and late-successional stages of each gradient. 4. We found that HFA and ability did not consistently shift with successional stage for all gradients, but were instead specific for each type of successional gradient. In coastal dunes HFA was positive for early-successional litter, in drift sands it was negative for mid-successional litter, and for ex-arable fields, HFA increased with successional time. Ability of decomposer communities was highest in mid-successional stages for coastal dunes and drift sands, but for ex-arable fields ability decreased throughout with successional time. High HFA was related to high litter C content and soil and organic matter content in soils and to low litter and soil nutrient concentrations. Ability did not consistently occur in successional stages with high or low litter quality. 5. Synthesis: Our findings show that specific environmental conditions, such as changes in litter or soil quality, along environmental gradients can shape the influence of HFA and ability on decomposition. In sites with strong HFA or ability, interactions between plants, litter and decomposer communities will be important drivers of nutrient cycling and hence have the potential to feedback to plant growth.
Field robots for the future farming of today
Nieuwenhuizen, Ard - \ 2018
Knowledge governance and policy: theoretical reflections
Gerritsen, A.L. ; Dotti, N.F. - \ 2018
In: Knowledge, Policymaking and Learning for European Cities and Regions / Dotti, N.F., Edward Elgar (New Horizons in regional science series ) - ISBN 9781786433633 - p. 244 - 258.
While innovation has become a major issue in territorial innovation policy, the scientific debate in this field has focused very little on issues such as knowledge for policymaking, learning and adaptation. This chapter explores the emerging notion of ‘knowledge governance’ and the challenges imposed by assuming a territorial perspective, due to the intrinsic limits of local learning communities and the need to anchor trans-territorial knowledge. The derived territorial knowledge governance framework will be explored by discussing the eight case studies presented in the second part of this volume, leading to reflections on the need for identifying realistic and situated knowledge governance arrangements.
Power in and over Cross-Sector Partnerships: Actor Strategies for Shaping Collective Decisions
Dewulf, A.R.P.J. ; Elbers, W. - \ 2018
Administrative Sciences 8 (2018)3. - ISSN 2076-3387
Cross-sector partnerships - institutional fields - issue field - collaboration - power sources - power strategies
While cross-sector partnerships are sometimes depicted as a pragmatic problem solving arrangements devoid of politics and power, they are often characterized by power dynamics. Asymmetries in power can have a range of undesirable consequences as low-power actors may be co-opted, ignored, over-ruled, or excluded by dominant parties. As of yet, there has been relatively little conceptual work on the power strategies that actors in cross-sector partnerships deploy to shape collective decisions to their own advantage. Insights from across the literatures on multiparty collaboration, cross-sector partnerships, interactive governance, collaborative governance, and network governance, are integrated into a theoretical framework for empirically analyzing power sources (resources, discursive legitimacy, authority) and power strategies (power over and power in cross-sector partnerships). Three inter-related claims are central to our argument: (1) the intersection between the issue field addressed in the partnership and an actor’s institutional field shape the power sources available to an actor; (2) an actor can mobilize these power sources directly in strategies to achieve power in cross-sector partnerships; and, (3) an actor can also mobilize these power sources indirectly, through setting the rules of the game, to achieve power over partnerships. The framework analytically connects power dynamics to their broader institutional setting and allows for spelling out how sources of power are used in direct and indirect power strategies that steer the course of cross-sector partnerships. The resulting conceptual framework provides the groundwork for pursuing new lines of empirical inquiry into power dynamics in cross-sector partnerships.
Increased water-use efficiency and reduced CO2 uptake by plants during droughts at a continental scale
Peters, W. ; Velde, I.R. van der; Schaik, Erik van; Miller, John B. ; Ciais, Philippe ; Duarte, Henrique F. ; Laan-Luijkx, I.T. van der; Molen, M.K. van der; Scholze, M. ; Schaefer, Kevin ; Vidale, Pier Luigi ; Verhoef, Anne ; Wårlind, D. ; Zhu, Dan ; Tans, Pieter P. ; Vaughn, Bruce ; White, James W.C. - \ 2018
Nature geoscience (2018). - ISSN 1752-0894 - 6 p.
Severe droughts in the Northern Hemisphere cause a widespread decline of agricultural yield, the reduction of forest carbon uptake, and increased CO2 growth rates in the atmosphere. Plants respond to droughts by partially closing their stomata to limit their evaporative water loss, at the expense of carbon uptake by photosynthesis. This trade-off maximizes their water-use efficiency (WUE), as measured for many individual plants under laboratory conditions and field experiments. Here we analyse the 13C/12C stable isotope ratio in atmospheric CO2 to provide new observational evidence of the impact of droughts on the WUE across areas of millions of square kilometres and spanning one decade of recent climate variability. We find strong and spatially coherent increases in WUE along with widespread reductions of net carbon uptake over the Northern Hemisphere during severe droughts that affected Europe, Russia and the United States in 2001–2011. The impact of those droughts on WUE and carbon uptake by vegetation is substantially larger than simulated by the land-surface schemes of six state-of-the-art climate models. This suggests that drought-induced carbon–climate feedbacks may be too small in these models and improvements to their vegetation dynamics using stable isotope observations can help to improve their drought response.
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