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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Nieuwe methoden voor bestrijding vanbodemplagen in de glastuinbouw. Deel 1: Biologie en bestrijding van Lyprauta sp. /
Kruidhof, Marjolein ; Woelke, Joop ; Vijverberg, Ruben ; Català-Senent, Laura ; Vijverberg, Roland - \ 2018
Bleiswijk : Wageningen University & Research, BU Glastuinbouw (Wageningen University & Research, BU Glastuinbouw rapport WPR-784) - 54
In de teelt van Phalaenopsis orchideeën wordt belangrijke schade veroorzaakt door zogenaamde ‘potwormen’, feitelijk muggenlarven van de familie Keroplatidae (langhoornmuggen). Deze larven, welke zich in het substraat bevinden, prederen in eerste instantie op bodemorganismen. Ze veroorzaken echter ook vraatschade aan wortelpunten, wat leidt tot een algehele groeivertraging. Zelfs bij lage aantallen langhoornmug larven - meestal zit er maar één larve in een pot - wordt de schadedrempel al overschreden door het relatief lage aantal wortels van Phalaenopsis. In dit rapport is het onderzoek beschreven naar a) de biologie van langhoornmuggen, met name naar Lyprauta cambria, en b) verschillende manieren om L. cambria te bestrijden, en/of ervoor te zorgen dat de larven minder schade berokkenen aan de wortelpunten van Phalaenopsis---In the cultivation of Phalaenopsis orchids important damage is caused by so-called ‘potworms’, which in reality are the larvae of the Keroplatidae family (fungus gnats). These larvae live in the substrate, and primarily predate on soil-dwelling organisms. However, they also cause feeding damage to the root tips, leading to a reduction in overall plant growth. Even at low Keroplatidae density – mostly only a single larva per pot is present – the damage threshold is often exceeded in Phalaenopsis because of its relatively low number of roots. In this report research addressing a) the biology of Keroplatidae larvae, with special focus on Lyprauta cambria, and b) different ways to control L. cambria, and/or reduce the damage that the larvae cause to the root tips of Phalaenopsis is described
Macro- and micro- plastics in soil-plant system : Effects of plastic mulch film residues on wheat (Triticum aestivum) growth
Qi, Yueling ; Yang, Xiaomei ; Pelaez, Amalia Mejia ; Huerta Lwanga, Esperanza ; Beriot, Nicolas ; Gertsen, Henny ; Garbeva, Paolina ; Geissen, Violette - \ 2018
Science of the Total Environment 645 (2018). - ISSN 0048-9697 - p. 1048 - 1056.
Agroecosystem - Biodegradable mulch film - Microplastics - Plant growth - Plastic residues

Plastic residues have become a serious environmental problem in the regions with intensive use of plastic mulching. Even though plastic mulch is widely used, the effects of macro- and micro- plastic residues on the soil-plant system and the agroecosystem are largely unknown. In this study, low density polyethylene and one type of starch-based biodegradable plastic mulch film were selected and used as examples of macro- and micro- sized plastic residues. A pot experiment was performed in a climate chamber to determine what effect mixing 1% concentration of residues of these plastics with sandy soil would have on wheat growth in the presence and absence of earthworms. The results showed that macro- and micro- plastic residues affected both above-ground and below-ground parts of the wheat plant during both vegetative and reproductive growth. The type of plastic mulch films used had a strong effect on wheat growth with the biodegradable plastic mulch showing stronger negative effects as compared to polyethylene. The presence of earthworms had an overall positive effect on the wheat growth and chiefly alleviated the impairments made by plastic residues.

Testing for complementarity in phosphorus resource use by mixtures of crop species
Li, Chunjie ; Kuijper, T.W.M. ; Werf, Wopke van der; Zhang, Junling ; Li, Haigang ; Zhang, Fusuo ; Hoffland, Ellis - \ 2018
Plant and Soil (2018). - ISSN 0032-079X - 15 p.
Competition - Complementarity - Intercrop - Phosphorus - Resource partitioning

Aims: The phosphorus (P) resource partitioning hypothesis assumes that dissimilarity in P acquisition traits among plant species leads to enhanced P uptake by crop combinations compared with their sole crops. We developed and implemented a test for this hypothesis. Methods: Two pot experiments were conducted with quartz sands. In Experiment 1, the ability of the crop species to acquire P from sparingly soluble sources (Ca phosphate (CaP), phytate (PhyP) and P-coated Fe (hydr)oxide (FeP)) was tested. In accordance with the species performances in Experiment 1, combinations of millet/chickpea and cabbage/faba bean (which have dissimilar P acquisition traits) and wheat/maize (which have similar traits) were selected for Experiment 2. The biomass production and P uptake were compared between the sole crops and species combinations as well as between the single and mixed P sources. Results: A dissimilarity in P acquisition traits enhanced P uptake by millet/chickpea on CaP/PhyP (as expected) but not by cabbage/faba bean on FeP/PhyP. Despite their similar P acquisition traits, we found enhanced P uptake by wheat/maize on CaP/PhyP. Conclusions: Because of complicating factors such as unstable P acquisition traits and competitive inequality between species, the conditions under which the P resource partitioning hypothesis can be tested are limited. This challenge complicates designing for complementarity in soil P pools by intercrops.

What root traits determine grass resistance to phosphorus deficiency in production grassland?
Ros, Mart B.H. ; Deyn, Gerlinde B. de; Koopmans, Gerwin F. ; Oenema, Oene ; Groenigen, Jan Willem van - \ 2018
Journal of Plant Nutrition and Soil Science 181 (2018)3. - ISSN 1436-8730 - p. 323 - 335.
P acquisition - root characteristics - root length - structural equation modeling - yield

Grasslands are a major form of agricultural land use worldwide. Current and future declines of phosphorus (P) inputs into production grasslands necessitate a shift towards selecting grass species based on high efficiency under suboptimal, rather than optimal P conditions. It is therefore imperative to identify key root traits that determine P acquisition of grasses in soils with a low P status. In a 9-month greenhouse experiment, we grew eight common grass species and cultivars on a soil with a low P status and related root morphological traits to their performance under P-limiting conditions. We applied (P1) or withheld (P0) P fertilization while providing adequate amounts of all other nutrients. Omitting P fertilization greatly reduced yield and nutrient acquisition for the various grass species. Biomass production differed significantly (P < 0.1%) among species and P fertilization treatments, varying from 17.1 to 72.1 g pot−1 in the P0 treatment and from 33.4 to 85.8 g pot−1 in the P1 treatment. Root traits were species-specific and unresponsive to P fertilization, but overall we observed a trade-off between root biomass and specific root length. Structural equation modeling identified total root length as key factor with respect to resistance to P deficiency, especially when roots explored the subsoil. Optimizing root length and subsoil exploration could be the key to maintaining high productivity of production grasslands with decreasing P availability. This is relevant for both plant breeding programs and for composing seed mixtures.

What makes long-term investment decisions forward looking : A framework applied to the case of Amsterdam's new sea lock
Pot, W.D. ; Dewulf, A. ; Biesbroek, G.R. ; Vlist, M.J. van der; Termeer, C.J.A.M. - \ 2018
Technological Forecasting and Social Change 132 (2018). - ISSN 0040-1625 - p. 174 - 190.
Forward-looking decisions - Future anticipation - Infrastructure investments - Public sector - Scenario use
Long-term investments challenge decision makers to look into the far future. Existing future studies often build upon a rational idea of decision making that does not help to explain why decision makers anticipate the future. In addition, existing studies do not provide a clear definition of what is considered as “forward looking”. This article proposes a framework that can be used to evaluate and explain for what reasons and based on what criteria decision makers take forward-looking investment decisions. We apply this framework to a specific decision-making case about a Dutch sea lock, making use of interviews (n = 16) and a content analysis of primary documents (n = 430). We find that not all investment decisions are necessarily forward looking. Secondly, we conclude from our case that decisions became forward looking because administrators used scenarios, visions, and flexible solutions to build support, avoid political risks and comply to formal rules. Scenario developers and urban planners could therefore involve administrators in early stages of the decision-making process to increase their awareness of the future towards which they are steering and provide them with alternative future paths. Furthermore, they could identify and use relevant institutional rules with forward-looking features to stimulate forward-looking decisions.
Arbuscular mycorrhizal fungi negatively affect nitrogen acquisition and grain yield of maize in a N deficient soil
Wang, Xin Xin ; Wang, Xiaojing ; Sun, Yu ; Cheng, Yang ; Liu, Shitong ; Chen, Xinping ; Feng, Gu ; Kuyper, Thomas W. - \ 2018
Frontiers in Microbiology 9 (2018)MAR. - ISSN 1664-302X
Arbuscular mycorrhizal fungi - Benomyl - Competition - Maize - Nitrogen uptake
Arbuscular mycorrhizal fungi (AMF) play a crucial role in enhancing the acquisition of immobile nutrients, particularly phosphorus. However, because nitrogen (N) is more mobile in the soil solution and easier to access by plants roots, the role of AMF in enhancing N acquisition is regarded as less important for host plants. Because AMF have a substantial N demand, competition for N between AMF and plants particularly under low N condition is possible. Thus, it is necessary to know whether or not AMF affect N uptake of plants and thereby affect plant growth under field conditions. We conducted a 2-year field trial and pot experiments in a greenhouse by using benomyl to suppress colonization of maize roots by indigenous AMF at both low and high N application rates. Benomyl reduced mycorrhizal colonization of maize plants in all experiments. Benomyl-treated maize had a higher shoot N concentration and content and produced more grain under field conditions. Greenhouse pot experiments showed that benomyl also enhanced maize growth and N concentration and N content when the soil was not sterilized, but had no effect on maize biomass and N content when the soil was sterilized but a microbial wash added, providing evidence that increased plant performance is at least partly caused by direct effects of benomyl on AMF. We conclude that AMF can reduce N acquisition and thereby reduce grain yield of maize in N-limiting soils.
Out of the pot and into the fire : Explaining the vulnerability of an endangered small headwater stream fish to black-bass Micropterus spp. invasion
Ellender, B.R. ; Weyl, O.L.F. ; Alexander, M.E. ; Luger, A.M. ; Nagelkerke, L.A.J. ; Woodford, D.J. - \ 2018
Journal of Fish Biology 92 (2018)4. - ISSN 0022-1112 - p. 1035 - 1050.
Behaviour - Endangered fish - Evolutionary response - Micropterus - Naïveté - Pseudobarbus afer
Introduced predatory fishes have had consistently severe consequences for native fishes in stream environments around the world, although the drivers of these effects are often unclear. In the Swartkops River headwaters in South Africa, native Eastern Cape redfin Pseudobarbus afer were always absent from sites occupied by non-native black basses Micropterus salmoides and Micropterus dolomieu, but generally co-occurred with the native predators Anguilla marmorata and Anguilla mossambica. A natural experiment provided by flood-mediated recolonization of black-bass occupied sites by P. afer demonstrated depletion in black-bass invaded sites. Field behavioural observations of P. afer indicated that they foraged among benthic cover during the day, but suspended in open water at night. As the nocturnal A. marmorata and A. mossambica foraged actively within structural cover at night and M. dolomieu and M. salmoides are diurnal or crepuscular predators, P .afer is thus optimized to avoid predation by native anguillid predators and not the functionally unique predatory black basses. The integration of distributional, temporal population dynamics and behavioural data suggests that the severe effects of Micropterus spp. are probably a consequence of prey naïveté and behaviour evolved to evade native predators.
Concurrentie, concentratie en rentabiliteit in de glastuinbouw in Nederland
Veerman, Kees - \ 2018
University. Promotor(en): Olaf van Kooten. - Wageningen : Wageningen University - ISBN 9789463438865 - 331


The expansion of the market area of the European Union has caused a strong increase of supply and demand of fresh horticulture products of the Dutch glasshouse sector on the European market. Consequently there is increased competition with companies from new European member states, producing against lower prices, as well as changes in production and sales structure. In the Dutch food horticulture sector this led to a large horizontal and vertical merger between most of the auctions and a number of large exporters. From 1996 to 1998 VTN/The Greenery changed from a co-operative auction into a co-operative trade organisation. In the floriculture sector only horizontal mergers took place between co-operative auctions. The wholesalers/exporters remained independent. At present there are two Flower Auctions, FloraHolland te Naaldwijk (market share 98%) and Plantion in Ede (2%).

Central research question

This thesis explores the development of market structure, market strategy and market results in the horticulture glasshouse sector over the last thirty-five years. The central research question is whether the difference in market structure and market strategy in the Dutch sectors of glasshouse vegetables and glasshouse cut flowers and pot plants is a significant cause to explain the difference in market results for the growers and their co-operative organisations.

The conceptual model

A number of theories and models have been studied derived from the Industrial Organisation Theory. This theory focuses on the analysis of branches of industries, industry chains and markets involved. It examines the relation between market structure (S), market conduct (C) and market performance (P) through the SCP-model (in Dutch: SGR-model). A description and explanation is given of the static SCP-model of Bain, the dynamic SGR-model of De Jong and the branch-analysing models of Porter and Daems. The conceptual model of competition, concentration and performance (figure 1.1) has been constructed from these models to analyse the Dutch horticulture glasshouse sectors.

Research of producers, sector research and research of auctions/sales organisations

From 2006-2008 three research projects on producers were conducted amongst 40 growers of vegetables, 40 growers of cut flowers and 40 growers of pot plants, all under glass. Data and opinions of growers about their company, market strategy and performance were gathered. In the same period sector research of the development of total production, imports and exports took place in the three sectors of the glasshouse industry on sector level, on the level of sales organisations and the wholesalers/ exporters. The gathered data have been analysed and tested on selected variables. In three different chapters temporary conclusions have been drawn. The most important business and market characteristics and research outcomes are discussed in three separate tables at the end of these three chapters and the associated appendices. The research of producers was expanded in 2015/2016 on the basis of the data of the research 2006-2008 with econometric research and multiple analysis of a number of the most important variables of market structure and market conduct to explain the market results (Lerner Index).

Results of sector research

The three horticulture sectors under glass show a positive development in yearly production and export value over a period of thirty-five years, besides a small decrease in 2009 and 2011, as a result of the banking and EHEC crisis. In the Dutch floriculture sector the average growing figures are a bit higher than in the food horticulture sector because of a stronger yearly increase in the production of pot plants. In all three sectors the production and export values are increased almost every year until the banking crisis in 2009. After 2010/2011 the sectors have been recovering.

Development of variables in Dutch horticulture glasshouse sector 1980-2016

The sector cut flowers under glass show a decrease of area and production (m2 glass) in The Netherlands. However, there is an increase of import and direct supply of cut flowers from foreign growers and Dutch companies from the southern part of Africa (roses, chrysanthemums etc.). All sectors profit from the growing import/re-export function of vegetables and fruit, cut flowers and pot plants from The Netherlands to neighbouring countries and trade partners in Europe. The high share of the sector variables domestic share and export share in all three sectors stimulate the development of production value, export value and prices.

Results of research into auctions/sales organisations

In the food horticulture and floriculture sectors there has been quite a difference in market strategy and market structure since 1998. In the sector vegetables under glass the degree of concentration of the four largest sales organisations (C4) has decreased to the level of before the merger (60%). In 1997 this figure was 96%. Also the share of growers of VTN/The Greenery in the area of Dutch vegetables under glass has decreased. VTN/The Greenery did not reach her target of 1996 with their strategy of horizontal and vertical concentration: organizing a larger bundling of the turnover of the Dutch auctions and wholesalers/exporters.

The search for a good working integration of horticultural production and trade in one company with an efficient and effective structure has not been completed yet and started in 2016 with a new sales organisation. The financial position of VTN/The Greenery on the European market is not strong. Since 1996 the annual turnover has strongly fluctuated between 0.9 and 1.5 billion euros, with a variation range of 25 to 30 %. The supply of their own members halved, just like the income out of commission. The position on the Dutch market is stable, on the most important European markets difficult. The return on investment is low. In 2015 and 2016 a careful recovery started after the difficult years of crisis 2009, 2011 and 2013.

Flower auctions FloraHolland and VBA showed a clear strategy and good results around the merger of 2007. The merger was a good example of a carefully implemented strategy of horizontal concentration, bringing together the interests of the flower auctions and their members. For FloraHolland the period of the crisis 2009-2011 was a test with success.

There was an expansion of horizontal concentration across the borders: a new joint venture auction Rhein-Maas, founded together with the German organisation Landgard and there was an integration with the import auction TFA in Aalsmeer. Both organisations are important for the market position of FloraHolland. In the Dutch floriculture sector under glass there are hardly any examples of vertical concentration of producers or sales organisations with wholesalers/exporters. There are examples, though, of vertical co-operation between these organisations and international retail, especially with the larger growers of pot plants.

The auction clock, physical and digital, is the most important sales method the flower auctions use daily. For most products there is a public pricing system. It provides a transparent process of supply and demand against sharp tariffs of the auction. For cut flowers as well as for pot and garden plants a large part of the product groups are sold by way of the auction clock, which mostly ensures a reliable reference price for mediation and personal selling and provides a good match of supply and demand and a ‘clean’ market. Attention to strengthen the position of the auction clock, especially with the selling of pot and garden plants, is important. The turnover of FloraHolland decreased in 2009 (bank crisis) and increased in 2010 and 2011 just above the level of 2008. Incomes out of services dropped. As costs decreased more than incomes, profits and solvency improved in this period.

In 2012 FloraHolland realised a turnover increase of 3% compared to 2011. However, the incomes out of services decreased. In 2013 the sector performed reasonably. The turnover of FloraHolland increased slightly but costs were higher than incomes and FloraHolland had an exploitation loss. 2014 was a year of slight recovery, 2015 and 2016 ended with an increasing turnover of 3 and 4%. Profit after tax in these years are 12 and 3 million euros. For most of the growers and customers the results in 2015 and 2016 were positive. The decision of the wholesale/export (VGB) to contribute again in the promotion costs of Bloemenbureau Holland was welcomed very positively. Along with the new strategy of 2020 FloraHolland is working on the strengthening and expansion of the physical and digital market places.

Research results of producers

On producers level there is also quite a difference in market strategy, structure and results between growers in the sectors of glasshouse vegetables and glasshouse cut flowers and pot plants. At present there is a fierce struggle to survive in each sector. It seems that the small grower of cut flowers and pot plants stands a better chance than the small grower in vegetables. The most striking single relations between structure, conduct and result will be mentioned.

Most striking single relations glasshouse vegetables

- The small company has relatively higher costs than the larger types. If the sales organisation uses the principle of ‘the user pays the total costs made’ this burden is rather heavy for the smallest companies.

- Auction growers mainly deliver round or grape tomatoes, the majority of independent growers choose for the special varieties. This influences the pricing process.

- Small and large auction growers differ significantly in business size from independent growers, but realise comparable margins. Large-scale production does not always lead to lower average costs and a better margin, but it does entail a greater risk of too much supply and low prices. Growers with a larger business size are faced with larger financial problems in difficult years than smaller ones.

- Horizontal concentration of the four largest growers of vegetables lies at a low level and their sales power is low. The concentration of the four largest sales organisations is about 60%.

- Vertically integrated auction growers are smaller in business size and invest less than non- integrated independent growers. They realise comparable margins.

- The importance of the sales organisation to realise good prices and margins for the members’ products seems rather small. Sharp purchase prices are of equal importance for the trade organisation and influence the margin of the members.

- Higher investments don’t produce higher results (directly). More innovative investments are needed to improve prices and margins.

Most striking single relations glasshouse cut flowers

- The small auction grower realises an expected smaller turnover and pays higher commission than the larger auction grower, member of a growers organisation. Although there is no significant relation between grower type and realised margin, higher commission can lead to higher prices and margins. Besides the higher price level, smaller growers realise a higher solvency than larger growers.

- Growers of roses under glass realise a higher margin than growers of chrysanthemums because of a wide and deep assortment.

- Small growers of cut flowers show comparable or better results than the larger ones.

- Horizontal concentration of the four largest growers of cut flowers lies, just like the sectors of vegetables and pot plants under glass, at a low level. The small auction grower has little market power and needs the sales organisation for reasonable prices and successful sales.

- There are no significant relations between the organisation of sales and growers’ turnover, realised margin and the height of commission. It looks as if every grower uses his own mix of marketing and sales activities in a way that no significant differences in results arise.

- Selling of cut flowers by means of the auction clock gives good results.

Most striking single relations glasshouse pot plants

- The smaller auction grower, with or without personal selling, realises an expected smaller turnover but a higher margin than the larger auction grower, member of a growers organisation.

- Smaller growers (in m2 glass) get higher results or results comparable to those of the larger ones. Old and new companies get comparable margins.

- Growers of green plants get a significant lower yearly turnover than growers of blooming pot plants. Green plants are often more unique than blooming plants. That is why growers of green plants get higher prices and margins.

- Horizontal concentration of the growers of pot plants lies, just like in the other sectors, at a low level. The small auction grower has little market power and needs the sales organisation for realising reasonable prices and successful sales.

- Like in the other sectors the small grower invests less in his business than the larger ones. Higher investments do not directly produce higher results. More innovative investments are needed to improve prices and margins.

- There is a significant relation between the organisation of sales and the yearly realised turnover: larger growers use more personal selling besides the sales services of the auction, as their own business activity or as an activity of the growers organisation.

Boarding out all sales activities to FloraHolland is effective especially for the small grower and enlarges the chance of realising a higher margin. Although he pays a higher commission, he realises a higher margin because of the positive relation between commission and margin.

Producers results through econometric research

Most striking multiple relations glasshouse vegetables

The results of the econometric analysis show that in the sector glasshouse vegetables membership of a growers association produces better results on average than membership of a traditional marketing corporation. Especially young producers with new ideas about the organisation of the company and vertical co-operation with on average large and modern companies are booking the best results.

Most striking multiple relations glasshouse cut flowers

Auction growers using the auction clock exclusively to sell their products realise a higher margin on average than growers using other selling methods. The membership of a growers association produces higher results on average than no membership and smaller companies get higher margins than large ones. Senior growers get higher results than junior growers. The auction clock is the best guarantee for realising higher margins. It seems that in the sector cut flowers a larger scale has less effect on the margin than producing ‘niche’ product types. For the latter the selling method via the auction clock plays an important role. Companies with ‘niche’ products have higher fixed costs although a higher margin gives fewer problems when it comes to finance the production.

Final conclusion

The answer to the central question confirms the following: the difference in market structure and market strategy in the Dutch sectors of glasshouse vegetables and glasshouse cut flowers is a significant cause to explain the difference in market results. If we follow the position and the results of the small grower in the sector glasshouse vegetables, we are looking at a producer in a tight spot with lower average results for the grower and his co-operation in comparison with the independent grower and his grower association. In the sector glasshouse cut flowers the position and results of the small auction clock grower is better in comparison with the grower who sells on his own or via a growers association.

The results of this research indicate that in the sector glasshouse vegetables the highest margins are obtained by the independent growers associations, working either cooperativly with the classical co-operations or independent there from but in any case with their own marketing strategy. In the sector glasshouse cut flowers it is the grower selling through the auction clock who gets the highest margins. In the sector glasshouse pot plants, where the type of the product clearly differs from the perishable vegetables and cut flowers, there are too few data to draw conclusions.

Red clover varieties of Mattenklee type have higher production, protein yield and persistence than Ackerklee types in grass-clover mixtures
Hoekstra, N.J. ; Deyn, G.B. De; Xu, Y. ; Prinsen, Rianne ; Eekeren, N. van - \ 2018
Grass and Forage Science 73 (2018)2. - ISSN 0142-5242 - p. 297 - 308.
Breeding - Morphology - Nutritive value - Plant traits - Trifolium pratense L.

Dairy farmers have increased interest in multiyear red clover-ryegrass ley pasture swards because of their high productivity and protein concentration but the adoption of such mixtures has been restricted because of poor persistency of many red clover cultivars currently used. We aimed (i) to assess dry-matter yield (DMY), persistence and nutritive value of four Mattenklee and four Ackerklee cultivars and (ii) to investigate the underlying plant morphological traits. We conducted a 4-year field experiment with red clover-ryegrass mixtures, in combination with a short-term pot experiment in which the red clover cultivars were grown both in monoculture and in mixture with Lolium perenne L. In the field, Mattenklees showed higher production (on average 42% higher) and clover content (on average 34% higher) in the third and fourth year of production compared to Ackerklees. In the fourth year, Mattenklees had slightly lower digestibility and lower protein concentration compared to Ackerklees cultivars; however, the digestible DMY and the protein yield were higher for Mattenklees. Both persistence and nutritive value of the different red clover cultivars were closely correlated with plant morphological traits. For stem length, there was close correlation (r > .77) between the results from the pot experiment and the field experiment, suggesting that stem length may be an important trait for plant breeding.

Dynamics of Soil Bacterial Communities Over a Vegetation Season Relate to Both Soil Nutrient Status and Plant Growth Phenology
Francioli, Davide ; Schulz, Elke ; Buscot, François ; Reitz, Thomas - \ 2018
Microbial Ecology 75 (2018)1. - ISSN 0095-3628 - p. 216 - 227.
B-ARISA fingerprinting - Inoculation of sterilized soil - Niche and neutral assemblage processes - Plant-soil interactions - Soil bacterial communities
Soil microorganisms regulate element cycling and plant nutrition, mediate co-existence of neighbors, and stabilize plant communities. Many of these effects are dependent upon environmental conditions and, in particular, on nutrient quality and availability in soils. In this context, we set up a pot experiment in order to examine the combined effects of soil nutrient availability and microbial communities on plant-soil interactions and to investigate assemblage rules for soil bacterial communities under changed nutrient conditions. Four gamma-sterilized soils, strongly differing in their nutrient contents, were obtained from different fertilization treatments of a centenary field experiment and used to grow communities of grassland plants. The sterilized soils were either self- or cross-inoculated with microbial consortia from the same four soils. Molecular fingerprinting analyses were carried out at several time points in order to identify drivers and underlying processes of microbial community assemblage. We observed that the bacterial communities that developed in the inoculated sterilized soils differed from those in the original soils, displaying dynamic shifts over time. These shifts were illustrated by the appearance of numerous OTUs that had not been detected in the original soils. The community patterns observed in the inoculated treatments suggested that bacterial community assembly was determined by both niche-mediated and stochastic-neutral processes, whereby the relative impacts of these processes changed over the course of the vegetation season. Moreover, our experimental approach allowed us not only to evaluate the effects of soil nutrients on plant performance but also to recognize a negative effect of the microbial community present in the soil that had not been fertilized for more than 100 years on plant biomass. Our findings demonstrate that soil inoculation-based approaches are valid for investigating plant-soil-microbe interactions and for examining rules that shape soil microbial community assemblages under variable ecological conditions.
Vermindering emissie van meststoffen met controlled released fertilizers (CRF) bij potorchidee (Phalaenopsis)
Kromwijk, Arca ; Haaster, Bram van; Steenhuizen, Johan - \ 2017
Bleiswijk : Wageningen University & Research, BU Glastuinbouw (Rapport WPR 703) - 46
In the Netherlands, the government and horticultural industry have agreed to lower the emission of nutrients to the environment. Previous research in pot orchid cultivation research showed that the reuse of drain water can lower the emission of nutrients significantly and had no adverse effects on plant growth or disease incidence. For further reduction of the emission of nutrients research into the effects of controlled released fertilizers (CRF) and reusing drain water (recirculation) in Phalaenopsis was conducted at Wageningen University & Research, Business Unit Greenhouse Horticulture in Bleiswijk. Two treatments with CRF were compared with a treatment without CRF with reusing drain water. The EC in the drain water of the treatments with CRF was 30% to 60% lower and the total amount of N in the drain water was 40 to 75% lower than in the treatment without CRF. This research is funded by the Phalaenopsis growers in the Netherlands, ICL Specialty Fertilizers, Top Sector Horticulture & Propagation Materials and Foundation Program Fund Greenhouse Horticulture.
Propagation by Cuttings
Miguel Costa, Joaquim ; Heuvelink, Ep ; Pol, Peter van de - \ 2017
In: Reference Module in Life Sciences / Roitberg, Bernard D., Elsevier - ISBN 9780128096338
Propagation of roses by stem cuttings is one of the simplest and most used methods to propagate this ornamental species. Indeed, most of old roses, English roses, miniatures and some rootstocks are commonly propagated by cuttings because they can root easily and, further, grow vigorously on their own roots. Every year, millions of roses are propagated by cuttings to support the needs of different sectors (e.g., production of rootstocks, cut roses, garden roses, and pot roses). In this article, we describe some of the main anatomical, ecophysiological and morphological aspects related to adventitious root formation in rose cuttings and the main internal and external determinants influencing rooting and final quality of rose starting material (rooted material ready to plant). Relevant strategies and developments in rose propagation by cuttings are presented and discussed.
Forward-looking investment decisions about end-oflifetime infrastructure: the role of politics and rules in investments in a Dutch sea lock
Pot, W.D. - \ 2017
The forward-looking capacity of local governments. An assessment of investment plans in municipal water infrastructure
Pot, W.D. - \ 2017
Wat is beter: glas, blik, vriezer of vers? Vers ingeblikt
Zwietering, Marcel - \ 2017

Groenten kun je kopen in pot of blik. Het ligt in dozen in de vriezer en in zakken in de koeling. En er is natuurlijk de versafdeling. Hoe blijven groenten het best vers?

Vooruitziende beslissingen over vervanging van waterinfrastructuur
Pot, Wieke - \ 2017
Speaker and organisor of Symposium Vooruitziende beslissingen over vervanging van waterinfrastructuur, 10 mei 2017, Urk
The forward-looking capacity of local governments. An assessment of investment plans in municipal water infrastructure
Pot, Wieke - \ 2017
Eten wat de pot schaft: dieetonderzoek bruinvissen
Mairo, Amy ; Nierop, A. van; Cremer, J.S.M. ; IJsseldijk, Lonneke ; Leopold, M.F. - \ 2017
Zoogdier 28 (2017)4. - ISSN 0925-1006 - p. 8 - 9.
Afgelopen zomer keurde staatssecretaris Van Dam van het ministerie van Economische Zaken de ‘Gedragscode natuurinclusief renoveren’ in beginsel goed. De gedragscode is ontwikkeld om bij het isoleren van gebouwen negatieve effecten op beschermde soorten te voorkomen bij de uitvoer van het ambitieuze project Stroomversnelling. De Zoogdierverenging is kritisch over de gedragscode en diende een zienswijze in.
Plantmonitoring op basis van fotosynthese sensoren : Praktijktesten in de teelt van tomaat en gerbera
Kaiser, Elias ; Baeza Romero, Esteban ; Meinen, Esther ; Raaphorst, Marcel ; Kempkes, Frank ; Elings, Anne ; Pot, Sander ; Jalink, Vincent ; Voogt, Jan ; Dieleman, Anja - \ 2017
Bleiswijk : Wageningen University & Research, BU Glastuinbouw (Wageningen Plant Research rapport WPR-712) - 46
Wageningen University & Research, Business Unit Glastuinbouw has investigated two methods of monitoring crop photosynthesis that might be used in greenhouse horticulture: the crop photosynthesis monitor and the CropObserver. This project was funded by ‘Kas als Energiebron’ and executed together with PhenoVation and PlantDynamics. The data of the crop photosynthesis monitor were compared to those of the photosynthesis module of the crop growth model INTKAM. Furthermore, the pattern of stomatal opening during the day was calculated with the Stomata sensor. Measurements showed that the crop photosynthesis monitor was too sensitive to changes in window opening and in CO2 supply to determine the crop photosynthesis accurately. The CropObserver was useful in determining the relative light use efficiency of the crop. The best methods to accurately and reliably determine crop photosynthesis might be the following: 1. By a photosynthesis model (as in INTKAM) to calculate the crop photosynthesis, coupled to a sensor that monitors the crop status to register when the performance of the crop deviates from what might be expected, or 2. Via the CropObserver to which a module is added that determines the stomatal conductance and a measurement of the CO2 concentration which is necessary to translate the signal of the CropObserver to CO2 uptake by the crop
Need for clean water and recirculation to reduce emissions of plant protection products from soilless cultivation
Vermeulen, T. ; Os, E.A. van; Linden, A.M.A. van der; Wipfler, E.L. - \ 2017
In: Proceedings of the ICESC2015. - International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611726 - p. 87 - 93.
Covered crops - Pesticides - Risk assessment - Substrate cultivation

Soilless cultivation suggests a closed system of water flows, the principal of which are (drip) irrigation evaporation and - in more high-tech systems -condensation water. However, in practice growers discharge water during the process of filter cleaning and also actively discharge water due to high levels of sodium or contamination with chemical or biological components. On average in the Dutch greenhouse situation 2-5% of the annual irrigated water is discharged annually. These discharges lead to pollution of surface water with nutrients as well as (residues of) plant protection products (PPPs). This awareness led in 2008 to the start of a working group that aimed to develop a risk evaluation tool for pesticide authorisation in Europe. The evaluation tool consists of a modelled approach for determining expected concentrations in surface water based on a reference scenario per crop i.e., a description of an actual situation including the technical layout of the glasshouse, the climatological year and the receiving ditch For two currently registered PPPs that are used in spray applications, the annual emission to surface water was calculated using different scenarios. As scenarios, substrate-based rose production and pot plant production were selected in combination with water sources of variable sodium concentrations that commonly occur and are used in The Netherlands. Sodium was found to be the only quantifiable argument for growers for active discharge, and therefore it was used as a leading principle for discharge in the water flow model. Water discharge was found to range from 80 to 700 m3 ha 1 year-1, leading to nitrogen emissions of 17 to 149 kg N ha∗ year-1. The emission of PPPs in these scenarios amounted to 0.02-3% of the total active substance that was applied.

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