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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    Ky’osimba Onaanya: understanding productivity of East African Highland banana
    Taulya, G. - \ 2015
    Wageningen University. Promotor(en): Ken Giller, co-promotor(en): Peter Leffelaar; P.J.A. van Asten. - Wageningen : Wageningen University - ISBN 9789462575615 - 167
    bananen - musa - droogte - voedingsstoffenbeschikbaarheid - kalium - stikstof - kunstmeststoffen - afrika - uganda - gewasgroeimodellen - beslissingsmodellen - drogestofverdeling - groeianalyse - licht - fenotypische variatie - bananas - musa - drought - nutrient availability - potassium - nitrogen - fertilizers - africa - uganda - crop growth models - decision models - dry matter distribution - growth analysis - light - phenotypic variation

    Over 30 million people in East Africa depend on East African highland bananas for food and income. The bananas are grown with limited additions of nutrients and no irrigation, despite widespread poor soil fertility and regular dry seasons. This thesis describes the effect of increasing rainfall and application of potassium and nitrogen fertilizers on banana growth and yields. In areas that receive less than 1100 mm of rainfall per year, additional rainfall increases yields by 65%. Application of potassium increases yields by 88%, while nitrogen is not required. A framework for computing banana growth and yield in response to the amount of water stored in the soil is described. Where the soil water storage capacity is low, mulching increases yields by 10% but it has no effect in areas where the soil water storage is high. This framework is envisaged to guide improvements in banana management and productivity in East Africa.

    Toepassing van NBS-aardappelsensing in de teelt van zetmeelaardappelen; IJkakker, veldproef 2014 't Kompas
    Geel, W.C.A. van; Schans, D.A. van der - \ 2015
    Lelystad : PPO AGV (PPO/PRI-rapport 655) - 28
    akkerbouw - bemesting - fabrieksaardappelen - stikstof - veldproeven - sensors - gewasgroeimodellen - gewaskwaliteit - arable farming - fertilizer application - starch potatoes - nitrogen - field tests - sensors - crop growth models - crop quality
    In het kader van IJkakker worden gewassensoren ingezet als monitor voor gewasontwikkeling. IJkakker heeft tot doel sensorgestuurde teeltmaatregelen te ontwikkelen. Het deelproject IJkakkerbemesting onderzoekt de mogelijkheden in de teelt van aardappelpootgoed en zetmeelaardappel. Uit een opname met gewassensoren kan een schatting worden gemaakt van de hoeveelheid stikstof die in een gewas zetmeelaardappel is opgenomen. Op basis van een eenvoudig groeimodel dat uit de temperatuursom de totale N-opname door het gewas berekent vanaf opkomst, kan de streefwaarde voor de N-opname op elke willekeurig tijdstip worden vastgesteld. Als de geschatte N-opname uit de sensordata lager is dan de streefopname op het tijdstip van sensing, wordt een stikstofbijmestgift berekend. Deze proef heeft als doel een stikstofbijmestsysteem voor zetmeelaardappel op basis van gewassensing te ontwikkelen en te vergelijken met een standaard praktijkbemesting en een bestaand N-bijmestsysteem gebaseerd op monstername van bodem en gewas.
    The African Greenhouse : a toolbox
    Elings, A. ; Hemming, S. ; Os, E.A. van; Campen, J.B. ; Bakker, J.C. - \ 2015
    Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1360) - 52
    greenhouse horticulture - greenhouses - greenhouse crops - greenhouse technology - protected cultivation - decision models - crop growth models - simulation models - africa - glastuinbouw - kassen - kasgewassen - kastechniek - teelt onder bescherming - beslissingsmodellen - gewasgroeimodellen - simulatiemodellen - afrika
    There is demand for a decision support tool to design greenhouse production systems in various climate zones and locations in Africa: the ‘Toolbox Adaptive Greenhouse Systems for Africa’. Selection of a limited number of climate zones that are representative for Africa limits the variation in designs to be evaluated and makes the approach more effective for the Netherlands supply industry. The toolbox will result in a number of greenhouse cultivation systems that are most suitable for a given location, weighing perspectives such as greenhouse type, greenhouse installation, climate, production and economic viability. The toolkit will follow the ‘adaptive greenhouse approach’ in which models for greenhouse, crop and finances are combined. This report provides a basis for the toolbox. An overview of African climates is given, followed by options for greenhouse design which are placed in the context of a number of production systems. The expected future developments and the transitions from current situations to likely future situations are briefly described. Anticipating likely future developments enables an analysis of the potential of a certain farm type, the requirements for further development, and the options for Netherlands involvement.
    Ontwerp algenteeltsysteem in kassen – een integraal rekenmodel
    Hemming, S. ; Sapounas, A. - \ 2013
    gewasgroeimodellen - modellen - algenteelt - gewasproductie - slangen (buizen) - teeltsystemen - glastuinbouw - biobased economy - crop growth models - models - algae culture - crop production - tubes - cropping systems - greenhouse horticulture - biobased economy
    Poster met onderzoeksinformatie. Doel van het onderzoek is het ontwikkelen van een integraal model dat de algenproductie in diverse configuraties buisvormige algenreactoren in kassen kan voorspellen.
    Modelling regional land use: the quest for the appropriate method
    Soltani Largani, A. - \ 2013
    Wageningen University. Promotor(en): Tom Veldkamp, co-promotor(en): Martha Bakker; Jetse Stoorvogel. - S.l. : s.n. - ISBN 9789461736574 - 153
    landgebruik - modelleren - gewasopbrengst - aardappelen - wintertarwe - gewasgroeimodellen - land use - modeling - crop yield - potatoes - winter wheat - crop growth models

    The demand for spatially-explicit predictions of regional crop-yield patterns is increasing. An approach to assess a priori and/or future ranges of alternative scenarios spatial yield patterns at the regional scale is the application of mechanistic crop growth simulation models (CGSMs) (e.g. Launary, 2002). However, two main problems emerge in the application of field-level CGSMs at regional scales. Firstly, the required input data on weather, soils, and management are often not available; and secondly, if they are, generally not at the required level of detail. There are two possible approaches to address the identified problems. One is replacing the CGSM by a metamodel (Kleijnen and Sargent, 2000). The second approach is a simple empirical model (e.g. Lobell et al., 2008).

    The modelling-approach choices and performances are context dependent. The context conditions that determine the best approach are input data requirements, problem definition, study sub-objective, the scale at which output results are expected, model end-users, and utilization of the output. The selection of the modelling approaches can be considered as one of the most difficult, and often ignored, steps to model crop yield at the regional level. However, a structured, systematic way of modelling-approach selection is lacking. In order to address this issue this thesis aimed to develop a framework for recommendable practices to model regional patterns of crop yield.

    We reviewed literature for existing approaches that have been used to overcome the problem of data availability for the application of CGSMs at the regional level. Then we used the review to formulate decision rules as to what approach to take under different circumstances. Which of the approaches should be used depends on the following questions: (i) do observations of the input variable allow to estimate semivariograms?; (ii) are there auxiliary data correlated to the target variable?; (iii) do the input variables exhibit spatial correlation?; and (iv) is there spatial correlation in the residuals of the regression that related auxiliary data to the target variable?. Summarized, the selection of possible approaches depends on the data availability, the spatial variability, the temporal variability, the correlations with other variables, the data acquisition methods, the expected accuracy from a particular approach used to describe spatial variability, and the sensitivity of the CGSM to the variable.

    We also evaluated different procedures (interpolate first, calculate later; calculate first, interpolate later) to simulate regional patterns of crop yields in the Carchi province in Northern Ecuador with field-level CGSMs. We also examined scaling effects that arise from spatial variability in input data by using different supports. Results demonstrated that the order of calculation and interpolation was of major importance, while aggregation had a minor effect on the regional patterns of potato yield. From an uncertainty propagation and variability point of view it is in general preferable to calculate first before interpolation.

    We compared and evaluated the performance of three different modelling approaches for their capacity to model regional patterns of crop yield for two different cases: potato yields in Carchi and wheat yields in Western Germany. Based on these findings, various criteria for selecting a modelling approach are defined including credibility, relevance, sensitivity, and user friendliness. The empirical model and the metamodel are very easy to use and transparent. However, their application domain is limited to the case study area. The application of the CGSM remains complex and the model functions as a black box. The strength of the CGSMs is that impacts over a wider range of conditions can be simulated, taking into account many factors in a way that would not be possible using empirical models and metamodels (Lobell and Burke, 2010). It can be concluded that the various modelling approaches each have their unique merit. Hence, the different modelling approaches are therefore complementary for the interpretation of the observed patterns. There is not a single optimal solution to modelling agricultural systems to model, e.g. regional yield patterns. Moreover, we analysed the effect of spatial aggregation on the performance of the modelling approaches. The results showed that aggregation of calculated data leads to less variability and increasing linear fits at higher aggregation levels. The spatial variability in the case study area determines how strong this effect is. Finally we conclude:

    Regional crop yield modelling is very sensitive to the choice of model-type and data used; This sensitivity is usually not specifically addressed and not properly and systematically documented in many studies; The outcomes of such modelling exercises cannot be properly used when the underlying decisions on model and data type and sensitivities are unknown; Without this crucial knowledge regional crop simulation models can be easily misused by non-specialists; Standard decision rules are proposed to document these choices in a standard format allowing cross comparisons of different approaches despite the often strong context dependency of the results.
    A climate robust integrated modelling framework for regional impact assessment of climate change
    Janssen, G. ; Bakker, A. ; Ek, R. van; Groot, A.M.E. ; Kroes, J.G. ; Kuiper, M. ; Schipper, P.N.M. ; Walsum, P.E.V. van; Wamelink, W. ; Mol, J. - \ 2013
    klimaatverandering - grondwaterstand - gewasgroeimodellen - evaporatie - grondwater - modellen - climatic change - groundwater level - crop growth models - evaporation - groundwater - models
    Decision making towards climate proofing the water management of regional catchments can benefit greatly from the availability of a climate robust integrated modelling framework, capable of a consistent assessment of climate change impacts on the various interests present in the catchments. In the Netherlands, much effort has been devoted to developing state-of-the-art regional dynamic groundwater models with a very high spatial resolution (25x25 m2). Still, these models are not completely satisfactory to decision makers because the modelling concepts do not take into account feedbacks between meteorology, vegetation/ crop growth, and hydrology. This introduces uncertainties in forecasting the effects of climate change on groundwater, surface water, agricultural yields, and development of groundwater dependent terrestrial ecosystems. These uncertainties add to the uncertainties about the predictions on climate change itself. In order to create an integrated, climate robust modelling framework, we coupled existing model codes on hydrology, agriculture and nature that are currently in use at the different research institutes in the Netherlands. The modelling framework consists of the model codes MODFLOW (groundwater flow), MetaSWAP (vadose zone), WOFOST (crop growth), SMART2-SUMO2 (soil-vegetation) and NTM3 (nature valuation). MODFLOW, MetaSWAP and WOFOST are coupled online (i.e. exchange information on time step basis). Thus, changes in meteorology and CO2-concentrations affect crop growth and feedbacks between crop growth, vadose zone water movement and groundwater recharge are accounted for. The model chain WOFOST-MetaSWAP-MODFLOW generates hydrological input for the ecological prediction model combination SMART2-SUMO2-NTM3. The modelling framework was used to support the regional water management decision making process in the 267 km2 Baakse Beek-Veengoot catchment in the east of the Netherlands. Computations were performed for regionalized 30-year climate change scenarios developed by KNMI for precipitation and reference evapotranspiration according to Penman-Monteith. Special focus in the project was on the role of uncertainty. How valid is the information that is generated by this modelling framework? What are the most important uncertainties of the input data, how do they affect the results of the model chain and how can the uncertainties of the data, results, and model concepts be quantified and communicated? Besides these technical issues, an important part of the study was devoted to the perception of stakeholders. Stakeholder analysis and additional working sessions yielded insight into how the models, their results and the uncertainties are perceived, how the modelling framework and results connect to the stakeholders’ information demands and what kind of additional information is needed for adequate support on decision making.
    Uncertainty in simulating wheat yields under climate change : Letter
    Asseng, S. ; Ewert, F. ; Rosenzweig, C. ; Jones, J.W. ; Supit, I. - \ 2013
    Nature Climate Change 3 (2013)9. - ISSN 1758-678X - p. 827 - 832.
    tarwe - gewasproductie - klimaatverandering - gewasgroeimodellen - wheat - crop production - climatic change - crop growth models - models - food - co2 - temperature - projections - adaptation - scenarios - ensemble - impacts
    Projections of climate change impacts on crop yields are inherently uncertain1. Uncertainty is often quantified when projecting future greenhouse gas emissions and their influence on climate2. However, multi-model uncertainty analysis of crop responses to climate change is rare because systematic and objective comparisons among process-based crop simulation models1, 3 are difficult4. Here we present the largest standardized model intercomparison for climate change impacts so far. We found that individual crop models are able to simulate measured wheat grain yields accurately under a range of environments, particularly if the input information is sufficient. However, simulated climate change impacts vary across models owing to differences in model structures and parameter values. A greater proportion of the uncertainty in climate change impact projections was due to variations among crop models than to variations among downscaled general circulation models. Uncertainties in simulated impacts increased with CO2 concentrations and associated warming. These impact uncertainties can be reduced by improving temperature and CO2 relationships in models and better quantified through use of multi-model ensembles. Less uncertainty in describing how climate change may affect agricultural productivity will aid adaptation strategy development andpolicymaking.
    Nu ook droge biologen in Wageningen
    Molenaar, J. - \ 2012
    Kennis Online 9 (2012)december. - p. 12 - 13.
    systeembiologie - modellen - computersimulatie - insect-plant relaties - gewasgroeimodellen - gewasbescherming - akkerbouw - systems biology - models - computer simulation - insect plant relations - crop growth models - plant protection - arable farming
    De systeembiologie, de wetenschapstak die computermodellen combineert met biologische waarnemingen, groeit wereldwijd onstuimig. Wageningen liep achter, maar speelt nu mee, zegt wiskundige Jaap Molenaar van Wageningen University, onderdeel van Wageningen UR.
    Uncertainty and sensitivity analysis of algae production models for flat panel photobioreactors
    Stefanov, M.S. ; Slegers, P.M. ; Boxtel, A.J.B. van - \ 2012
    gewasgroeimodellen - algen - algenteelt - oogstvoorspelling - fotobioreactoren - onderzoeksprojecten - biobased economy - biomassa productie - crop growth models - algae - algae culture - yield forecasting - photobioreactors - research projects - biobased economy - biomass production
    Poster met onderzoeksinformatie.
    Predictive modelling of large scale algae biomass production
    Slegers, P.M. ; Wijffels, R.H. ; Straten, G. van; Boxtel, A.J.B. van - \ 2012
    gewasgroeimodellen - algen - algenteelt - oogstvoorspelling - biomassa productie - cultuurmethoden - biobased economy - onderzoeksprojecten - crop growth models - algae - algae culture - yield forecasting - biomass production - cultural methods - biobased economy - research projects
    Poster met onderzoeksinformatie.
    Water en nutriënten gelimiteerde gewasopbrengst : koppeling van de modellen SWAP-ANIMAO-WOFOST
    Stolk, P.C. ; Kroes, J.G. - \ 2012
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2346) - 47
    bodemwater - agrohydrologie - bodemchemie - biogeochemie - stikstof - modellen - gewasgroeimodellen - soil water - agrohydrology - soil chemistry - biogeochemistry - nitrogen - models - crop growth models
    Dit rapport beschrijft een verkennende studie voor een methodiek waarin de bodem-nutriëntenhuishouding op dynamische wijze is gekoppeld aan gewasgroei. Voor deze studie is gewasgroei gesimuleerd met het model WOFOST, gekoppeld aan het hydrologisch model SWAP. Dit is uitgebreid met een dynamische koppeling met het biogeochemisch model ANIMO waardoor het mogelijk is terugkoppelingen tussen nutriënten, water en vegetatie te bestuderen. In een casestudie en verschillende modelexperimenten is nagegaan wat het effect is van een beperking in bodem-nutriëntenaanbod op gewasgroei en verdamping. De modelresultaten laten zien dat het veronderstelde effect van stikstoftekort op gewasgroei en verdamping aantoonbaar is en gekwantificeerd kan worden met het huidige modelinstrumentarium. Hierbij is het aanbod van water en nutriënten in detail gemodelleerd. De vraagkant vanuit het gewas is relatief eenvoudig gemodelleerd en vereist nadere studie om operationele toepassingen (bijvoorbeeld schade-berekeningen) mogelijk te maken.
    Teelt optimaliseren met simulatie in virtuele kas (interview met Pieter de Visser)
    Visser, P. ; Visser, P.H.B. de - \ 2012
    Groenten en Fruit Actueel 2012 (2012)25. - ISSN 0925-9694 - p. 11 - 11.
    computersimulatie - 3d visualisatie - gewasgroeimodellen - glastuinbouw - belichting - computer simulation - 3d visualization - crop growth models - greenhouse horticulture - illumination
    Een 3D-model dat belichtingssituaties in de kas nabootst biedt uitgebreide mogelijkheden om allerlei variaties door te rekenen op effectiviteit en zo de teelt te optimaliseren. Of om praktijkonderzoek gericht te ondersteunen. Binnen het programma Kas als Energiebron heeft Wageningen UR Glastuinbouw, in een door PT en EL&I gefinancierd project, onderzocht welke mogelijkheden een driedimensionaal model van gewassen kan bieden bij tomaat en roos.
    Scenario development and assessment of the potential impacts of climate and market changes on crops in Europe : Assessing the adaptive capacity of agriculture in the Netherlands to the impacts of climate change under different market and policy scenarios (AgriAdapt project)
    Ewert, F. ; Angulo, C. ; Rumbaur, C. ; Lock, R. ; Enders, A. ; Adenauer, M. ; Heckelei, T. ; Ittersum, M.K. van; Wolf, J. ; Rötter, R. - \ 2011
    Climate changes Spatial Planning - 49
    klimaatverandering - gewasproductie - gewasgroeimodellen - west-europa - climatic change - crop production - crop growth models - western europe
    The Netherlands are an important producer and exporter of agricultural products. Changes in climate, markets and policies may have a large impact on the agricultural sector and farmers will need to adapt to these changes. Sector and policy documents have, so far, insufficiently considered the impacts of climate change and increased climate variability on the sector.
    Literatuuronderzoek + kasproef = Groeimodel Gerbera
    Helm, Frank van der - \ 2011
    gerbera - crop growth models - agricultural research - plant development - ornamental horticulture - greenhouse horticulture
    Predictive modelling of large scale algal biomass production
    Slegers, Ellen - \ 2011
    algae culture - algae - biomass production - crop growth models - models - biobased economy
    From field to globe: upscaling of crop growth modelling
    Bussel, L.G.J. van - \ 2011
    Wageningen University. Promotor(en): Herman van Keulen; Martin van Ittersum, co-promotor(en): F. Ewert; Peter Leffelaar. - [S.l.] : S.n. - ISBN 9789461730152 - 212
    gewassen - gewasgroeimodellen - modelleren - computersimulatie - tarwe - maïs - klimaat - crops - crop growth models - modeling - computer simulation - wheat - maize - climate

    Recently, the scale of interest for application of crop growth models has extended to the region or even globe with time frames of 50-100 years. The application at larger scales of a crop growth model originally developed for a small scale without any adaptation might lead to errors and inaccuracies. Moreover, application of crop growth models at large scales usually gives problems with respect to missing data.

    Knowledge about the required level of modelling detail to accurately represent crop growth processes in crop growth models to be applied at large scales is scarce. In this thesis we analysed simulated potential yields, which resulted from models which apply different levels of detail to represent important crop growth processes. Our results indicated that, after location-specific calibration, models in which the same processes were represented with different levels of detail may perform similarly. Model performance was in general best for models which represented leaf area dynamics with the lowest level of detail. Additionally, the results indicated that the use of a different description of light interception significantly changes model outcomes. Especially the representation of leaf senescence was found to be critical for model performance.

    Global crop growth models are often used with monthly weather data, while crop growth models were originally developed for daily weather data. We examined the effects of replacing daily weather data with monthly data. Results showed that using monthly weather data may result in higher simulated amounts of biomass. In addition, we found increasing detail in a modelling approach to give higher sensitivity to aggregation of input data.

    Next, we investigated the impact of the use of spatially aggregated sowing dates and temperatures on the simulated phenology of winter wheat in Germany. We found simulated winter wheat phenology in Germany to be rather similar using either non-aggregated input data or aggregated input data with a 100 km × 100 km resolution.

    Generation or simulation of input data for crop growth models is often neces­sary if the model is applied at large scales. We simulated sowing dates of several rainfed crops by assuming farmers to sow either when temperature exceeds a crop-specific threshold or at the onset of the wet season. For a large part of the globe our methodology is capable of simulating reasonable sowing dates. To simulate the end of the cropping period (i.e. harvesting dates) we developed simple algorithms to generate unknown crop- and location-specific phenological parameters. In the main cropping regions of wheat the simulated lengths corresponded well with the observations; our methodology worked less well for maize (over- and underestimations of 0.5 to 1.5 month). Importantly, our evaluation of possible consequences for simulated yields related to uncertainties in simulated sowing and harvesting dates showed that simulated yields are rather similar using either simulated or observed sowing and harvesting dates (a maximum difference of 20%), indicating the applicability of our methodology in crop productivity assessments.

    The thesis concludes with a discussion on a proposed structure of a global crop growth model which is expected to simulate reasonable potential yields at the global scale if only monthly aggregates of climate data at a 0.5° × 0.5° grid are available. The proposed model consists of a forcing function, defined in terms of sigmoidal and quadratic functions to represent light interception, combined with the radiation use efficiency approach, and phenology determining the allocation of biomass to the organs of the crop. Within the model sowing dates and pheno­logical cultivar characteristics are simulated. Based on the proposed model the thesis finally derives directions for future research to further enhance global crop growth modelling.

    A greenhouse crop production system for tropical lowland conditions
    Impron, S. - \ 2011
    Wageningen University. Promotor(en): Gerard Bot, co-promotor(en): Silke Hemming; Anne Elings. - [S.l.] : S.n. - 117
    teelt onder bescherming - kassen - glastuinbouw - tropisch klimaat - laaglandgebieden - solanum lycopersicum - gewasgroeimodellen - simulatiemodellen - modelleren - protected cultivation - greenhouses - greenhouse horticulture - tropical climate - lowland areas - solanum lycopersicum - crop growth models - simulation models - modeling

    Key words: tropical lowland climate, tropical lowland greenhouse, plastic greenhouse, near

    infrared radiation (NIR) reflecting plastic, greenhouse climate model, determinate tomato, crop

    growth, development, truss appearance rate, crop simulation model, INTKAM.

    The goal of this research was to improve greenhouse crop production under tropical

    lowland conditions. The dynamics of greenhouse climate were analyzed using a simple

    greenhouse climate model (GCM), while the growth and development of a determinate

    tomato crop were quantified using the INTKAM greenhouse crop simulation model. By

    combining the GCM and INTKAM models, ways to improve tomato production under

    tropical lowland greenhouse were investigated. Model calculations were calibrated and

    validated with experiments in six prototype greenhouses with three different near infrared

    (NIR) transmissivities during three periods with different tropical lowland climate

    characteristics.

    The greenhouses having high natural ventilation capacity showed a climate closely

    coupled to the outdoor climate. Greenhouse air temperature TAir was affected more by

    variation in ventilation and leaf area index than by the applied NIR transmission.

    Simulation shows that lowering TAir can be achieved by: (i) reducing near infrared

    radiation (NIR) transmission especially for bigger greenhouses and humid conditions, (ii)

    increasing ventilation openings and (iii) transpiration cooling, especially under hot and

    dry conditions. GCM study indicated that naturally ventilated model greenhouses of up to

    size of 14400 m2 were capable to create TAir close to or lower than outdoor air

    temperature Tout when the greenhouse crops had leaf area index of higher than 0.5.

    Crops with low number of trusses produced substantially lower fruit weight than crops

    with high number of trusses. Determinate tomato clearly exhibit high fruit abortion, with

    the number of fruits per truss decreasing as truss number increases. This partly can be

    explained by low source – sink strength ratio during the productive period. Effort to

    increase tomato production might require adequate crop management aimed at finding

    the appropriate source – sink balance. Scenario studies revealed that fruit production by a

    determinate tomato crop can be increased slightly by using zero NIR transmittance plastic

    film and by planting three crops per year (which is current practice). However, when the

    number of fruits can be maintained constant through appropriate crop management

    measures, the production would increase with increasing fruit load and the lengthening

    production period through fewer plantings per year.

    Literatuuronderzoek bloei Gerbera: Verkenning informatie voor gewasgroeimodel Gerbera
    Eveleens-Clark, B.A. ; Helm, F.P.M. van der; Visser, P.H.B. de - \ 2011
    Bleiswijk : Wageningen UR Glastuinbouw (Rapporten GTB 1098) - 36
    cultuurmethoden - snijbloemen - gerbera - plantenontwikkeling - gewasgroeimodellen - klimaatregeling - daglicht - bloei - landbouwkundig onderzoek - literatuuroverzichten - cultural methods - cut flowers - gerbera - plant development - crop growth models - air conditioning - daylight - flowering - agricultural research - literature reviews
    Er is behoefte om de groeimodellen voor gerbera te verbeteren door de assimilatenverdeling binnen het gewas in relatie tot omgevingsfactoren en blad- en bloemafsplitsing in beeld te brengen. Dit is nodig om te kunnen sturen op maximale bloemproductie met behoud van kwaliteit. Het is niet bekend wat de optimale verhouding is tussen daglengte, tempera - tuur en lichtniveau. Hierbij is de dynamiek van wisselende klimaatcondities in de tijd en de steeds wijzigende status van het gewas een extra complicerende factor. Met een model dat de processen integreert, kan dit beter in beeld gebracht worden. Zo kan bijvoorbeeld het dichttrekken van een scherm nodig zijn voor het korte dag effect, maar nadelig zijn voor planttemperatuur en/of drogestofproductie en op termijn een dunner gewas geven. Dit rapport omhelst deel 1A van het project, een literatuurstudie, waarin een overzicht gemaakt is van bestaande kennis over het effect van klimaatfactoren op groei, fotosynthese, ademhaling, afsplitsing, droge stof verdeling en bladoppervlak. De dynamiek tussen de verschillende klimaatfactoren en de toepassing van bestaand onderzoek voor het model is ook aan de orde gesteld.
    Mapping maize yield variability in Mali
    Conijn, J.G. ; Hengsdijk, H. ; Rutgers, B. ; Jongschaap, R.E.E. - \ 2011
    Wageningen : Plant Research International (Report / Plant Research International 375) - 18
    zea mays - maïs - opbrengsten - simulatiemodellen - gewasgroeimodellen - mali - zea mays - maize - yields - simulation models - crop growth models - mali
    Groemodel Freesia
    Labrie, Caroline - \ 2010
    freesia - crop growth models - ornamental crops - greenhouse horticulture
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