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A physiologically-based model of Cirsium arvense and Tussilago farfara growth and control Organic Eprints
Holst, Niels; Riemens, Marleen; Rasmussen, Ilse A..
Perennial herbs can be difficult to manage because of their underground storage organs which live sheltered from observation and control. In this paper, we describe the development of a population dynamics model for two perennial weeds, Cirsium arvense and Tussilago farfara. The model is physiologically based and includes plant growth and development, and mowing as a control option. Model performance was compared with field data from monospecific stands of C. arvense in Denmark and Netherlands and of T. farfara in Denmark. Finally, optimal mowing strategies were explored with the model.
Tipo: Journal paper Palavras-chave: Weed management.
Ano: 2012 URL: http://orgprints.org/20650/4/20650.pdf
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A universal simulator for ecological models Organic Eprints
Holst, Niels.
To most modellers, ecological models are primarily about ecology. A model is a condensed summary of an ecosystem written in the language of mathematics and logic. While modellers with a mathematical inclination may prefer stringent model formulations, that allow formal mathematical analysis, most modellers in ecology prefer heterogeneus, composite models permitting only numerical analysis; they are computational modellers who implement their models in software, which then itself becomes both tool and object in the ensuing analysis. The design and implementation details of this software is largely neglected. But this paper is only about this: the proper design and implementaion of ecological models.
Tipo: Journal paper Palavras-chave: Systems research and participatory research.
Ano: 2012 URL: http://orgprints.org/20632/7/20632.pdf
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Cirsium arvense responses to stubble cultivation and catch crops in organic cropping systems Organic Eprints
Holst, Niels; Melander, Bo; Rasmussen, Ilse A.; Hansen, Preben Klarskov.
Field studies on perennial weeds, such as Cirsium arvense, are necessary to study the systemic effects of weed control. In this study we analyse the responses in above-ground C. arvense biomass and crop yield from results obtained in two organic field experiments, both combining stubble cultivation with post-harvest catch crops. A range of catch crops was investigated, varying in both species mixture and method of establishment, yet stubble cultivation was the only treatment found to reduce C. arvense density. The effect was even seen only in one year when a harsh winter acted synergistically with soil tillage. C. arvense exhibited density-dependent growth, in terms of above-ground biomass at harvest, with an estimated max. exponential growth rate of...
Tipo: Journal paper Palavras-chave: Weed management.
Ano: 2012 URL: http://orgprints.org/20590/4/20590.pdf
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Collaborative weed modelling with Universal Simulator Organic Eprints
Holst, Niels.
Universal Simulator is • open-source • modular • extendible • re-usable Universal Simulator includes • the INTERCOM model of plant growh • the Conductance model of plant growth • an annual weed demographic model • an insect demographic model • options to extend with any model and combine with the above
Tipo: Conference paper, poster, etc. Palavras-chave: Systems research and participatory research.
Ano: 2010 URL: http://orgprints.org/18813/2/18813.pdf
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Computer model for simulating the long-term dynamics of annual weeds Organic Eprints
Rasmussen, Ilse A.; Holst, Niels.
A simulation model of the population dynamics of annual weeds and how it is affected by crop rotation, cultivation practices and weed control was presented by Rasmussen et al. (2002). The model aims to predict the development of a certain weed species in order to plan crop rotation and cultivation practices to minimise the risk of proliferation. The model does not predict the exact number of weeds expected to be found in a certain year or crop, but rather the general development over a number of years. It included the most important processes of the weed life cycle: seed survival in the soil, seed placement in soil after tillage, seed germination depending on soil depth, time of year and tillage and weed physiological development. The component describing...
Tipo: Conference paper, poster, etc. Palavras-chave: Weed management.
Ano: 2004 URL: http://orgprints.org/3933/1/3933.doc
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Computer model for simulating the long-term dynamics of annual weeds: from seedlings to seeds Organic Eprints
Rasmussen, Ilse A.; Holst, Niels.
We developed a simple model to predict seed production from seedling density and estimated its six parameters for Chenopodium album and Papaver rhoeas from literature data, supplemented with field data on P. rhoeas seed production in Denmark. Parameter values were specified by their expected ranges rather than just point estimates, which enabled us to determine the expected ranges of seed production at given seedling densities. The model will be incorporated into a larger model framework presented earlier for a more complete description of annual weed seedbank dynamics in a crop rotation. We found the seed production (y) of P. rhoeas to be larger than reported earlier from UK; the relation to weed biomass (x) per m2 was curvilinear, y=6015∙x0.8153 seeds...
Tipo: Journal paper Palavras-chave: Weed management.
Ano: 2003 URL: http://orgprints.org/3434/1/3434.doc
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Concepts and tools for collaborative weed demographic modeling Organic Eprints
Holst, Niels.
Weed demography is the study of the long-term dynamics of weed populations. Weed demography is an essential part of weed science, yet, its complexity makes scientific progress slow. Generalities remain obscure while the accumulation of specific data continues unhindered. In this talk, I introduce some modelling concepts and tools that I hope will help us disinter general principles from this heap of data, we are adding to every day.
Tipo: Conference paper, poster, etc. Palavras-chave: Systems research and participatory research Education; Extension and communication.
Ano: 2009 URL: http://orgprints.org/17894/1/2009_Orlando_Niels_Holst.ppt
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Direct control of perennial weeds between crops – implications for organic farming Organic Eprints
Melander, Bo; Rasmussen, Ilse A.; Holst, Niels; Hansen, Preben Klarskov.
Perennial weeds can be a major constraint to organic crop production in several North European 26 countries. Preventive and cultural control measures may not suffice when infestations with perennials 27 become severe. Direct control actions applied between crops can then be necessary to reduce the 28 problems. We conducted two experiments, one on a sandy loam and one on a sandy soil, respectively, in 29 Denmark, with the aim of studying the efficacy of different implement types and strategies. The 30 treatments were employed against mixed stands of perennials after harvest of spring barley in two 31 consecutive years. Time of treatment, cultivation depth and combinations of implements constituted the 32 strategies. Treatment effects were evaluated in the...
Tipo: Journal paper Palavras-chave: Weed management.
Ano: 2012 URL: http://orgprints.org/22000/7/22000.pdf
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Direct control of perennial weeds between crops – implications for organic farming Organic Eprints
Melander, Bo; Rasmussen, Ilse A.; Holst, Niels; Hansen, Preben Klarskov.
Perennial weeds can be a major constraint to organic crop production in several North European 26 countries. Preventive and cultural control measures may not suffice when infestations with perennials 27 become severe. Direct control actions applied between crops can then be necessary to reduce the 28 problems. We conducted two experiments, one on a sandy loam and one on a sandy soil, respectively, in 29 Denmark, with the aim of studying the efficacy of different implement types and strategies. The 30 treatments were employed against mixed stands of perennials after harvest of spring barley in two 31 consecutive years. Time of treatment, cultivation depth and combinations of implements constituted the 32 strategies. Treatment effects were evaluated in the...
Tipo: Journal paper Palavras-chave: Weed management.
Ano: 2011 URL: http://orgprints.org/20625/4/20625.pdf
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Ikke-kemisk ukrudtsbekæmpelse – mekanisk og termisk Organic Eprints
Melander, Bo; Rasmussen, Ilse A.; Holst, Niels.
Kapitlet gennemgår den vigtigste viden omkring brugen af íkke-kemisk ukrudtsbekæmpelse i landbrugs- og havebrugsafgrøder. Der indgår både klassisk viden og helt nye forskningsresultater. Kapitlet anvendes af studerende på landbrugsskoler, men kan også anvendes af andre interesserede.
Tipo: Book chapter Palavras-chave: Weed management.
Ano: 2011 URL: http://orgprints.org/20610/4/20610.pdf
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Ikke-kemisk ukrudtsbekæmpelse - mekanisk og termisk Organic Eprints
Melander, Bo; Rasmussen, Ilse Ankjær; Holst, Niels; Bertelsen, Inger.
Gennemgang af de mest almindelige ikke-kemiske bekæmpelsesmetoder. Tidligere tiders erfaringer såvel som nye forsøgsresultater.
Tipo: Book chapter Palavras-chave: Weed management.
Ano: 2004 URL: http://orgprints.org/4589/1/4589.pdf
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Langsigtet balance i ukrudtsbestanden Organic Eprints
Rasmussen, Ilse A.; Melander, Bo; Hansen, Preben Klarskov; Holst, Niels.
Dokumentet beskriver hvorledes den langsigtede balance i ukrudtsbestanden kan simuleres ved hjælp af en populationsdynamisk model, samt hvordan balancen kan rykkes til landmandens fordel. f.eks ved hjælp af konkurrencestærke sorter
Tipo: Conference paper, poster, etc. Palavras-chave: Crop combinations and interactions; Weed management; Production systems.
Ano: 2004 URL: http://orgprints.org/3418/1/3418.pdf
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Modeling the effect of management strategies on the seed bank dynamics of volunteer oilseed rape Organic Eprints
Rasmussen, Ilse A.; Holst, Niels; Madsen, Kathrine Hauge.
Seeds of genetically modified (GM) crops remaining in the field after harvest may later emerge as volunteers. These can affect the purity of subsequently harvested crops and cause an uncontrolled flow of GM pollen into the agro-ecosystem. Management strategies that reduce these long-term effects of GM crops include (1) minimizing the input of GM seeds into the soil, (2) preventing proliferation by volunteers and (3) fast depletion of the soil GM seed bank. Formulation of such strategies requires knowledge of the biology of the GM plant (seed loss at or before harvest, seed survival, germination and emergence rates, reproduction, etc.) and of the effect of management practices on the different life stages. Of the GM crops considered for cultivation in...
Tipo: Conference paper, poster, etc. Palavras-chave: Crop health; Quality; Protection Weed management.
Ano: 2003 URL: http://orgprints.org/3934/1/3934.doc
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Resultater og erfaringer med rodukrudtsbekæmpelse i økologisk planteproduktion ved AU Organic Eprints
Melander, Bo; Rasmussen, Ilse A.; Holst, Niels.
Præsentation af forskningsresultater vedrørende rodukrudtsbekæmpelse i økologisk jordbrug udført ved Aarhus Universitet
Tipo: Conference paper, poster, etc. Palavras-chave: Weed management.
Ano: 2011 URL: http://orgprints.org/20620/4/20620.pdf
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Tolerance of four spring barley (Hordeum vulgare L.) varieties to weed harrowing Organic Eprints
Hansen, Preben Klarskov; Rasmussen, Ilse A.; Holst, Niels; Andreasen, Christian.
We investigated the tolerance to weed harrowing of four spring barley varieties and examined the possible interactions between varietal weed suppressive ability and two nutrient levels. Tolerance was defined as the combined effect of crop resistance (ability to resist soil covering) and crop recovery (the ability to recover in terms of yield). The weed harrowing strategy was a combination of one pre- and one post-emergence weed harrowing. In terms of yield, the four varieties responded significantly differently to weed harrowing and the response depended on nutrient level. At the lower nutrient level, weed harrowing caused an increase in yield of 4.4 hkg ha-1 for a strong competitor (cv. Otira), while there was no effect on yield at the higher nutrient...
Tipo: Journal paper Palavras-chave: Crop health; Quality; Protection Crop combinations and interactions Weed management Breeding; Genetics and propagation.
Ano: 2007 URL: http://orgprints.org/11292/1/Tolerance_of_four_spring_barley_%28Hordeum_vulgare%29_varieties_to_weed_harrowing.pdf
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Tolerance to weed harrowing in four spring barley varieties Organic Eprints
Hansen, Preben Klarskov; Rasmussen, Ilse A.; Holst, Niels; Andreasen, Christian.
The aim of this study was to investigate possible interactions between a preventive and a curativ method (combination of one pre and one post-emergence weed harrowing). We estimated the damages by weed harrowing in four pure varieties of spring barley, and analysed if there were differences in resistance and tolerance to weed harrowing between the varieties. As organic growing conditions are characterised by greater differences in nutrient levels, we further examined if there was any interactions between harrowing resistance and tolerance of the varieties and two nutrient level. Tolerance to weed harrowing was measured as an immediate effect (Resistance=how much of the plant is covered with soil after weed harrowing), a short-term effect (growth rate...
Tipo: Journal paper Palavras-chave: Crop health; Quality; Protection Crop combinations and interactions Weed management Breeding; Genetics and propagation.
Ano: 2006 URL: http://orgprints.org/7872/1/7872.doc
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Ukrudtsøkologi og -biologi Organic Eprints
Rasmussen, Ilse Ankjær; Holst, Niels; Graglia, Enrico; Hansen, Preben Klarskov; Melander, Bo; Mathiassen, Solvejg Kopp; Kudsk, Per; Jensen, Peter; Boelt, Birte; Madsen, Katrine Hauge.
Ukrudtsplanters livsprocesser, f.eks. spiring, vækst og blomstring, og samspil med andre organismer, f.eks. andet ukrudt, afgrøder og insekter.
Tipo: Book chapter Palavras-chave: Weed management.
Ano: 2004 URL: http://orgprints.org/4593/1/4593.pdf
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WeedML: a Tool for Collaborative Weed Demographic Modeling Organic Eprints
Holst, Niels.
WeedML is a proposed standard to formulate models of weed demography, or maybe even complex models in general, that are both transparent and straightforward to re-use as building blocks for new models. The paper describes the design and thoughts behind WeedML which relies on XML and object-oriented systems development. Proof-of-concept software is provided as open-source C++ code and executables that can be downloaded freely.
Tipo: Journal paper Palavras-chave: Systems research and participatory research Education; Extension and communication.
Ano: 2010 URL: http://orgprints.org/17893/1/wees%2D58%2D04%2D07.pdf
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WeedML: a Tool for Collaborative Weed Demographic Modeling Organic Eprints
Holst, Niels.
WeedML is a proposed standard to formulate models of weed demography, or maybe even complex models in general, that are both transparent and straightforward to re-use as building blocks for new models. The paper describes the design and thoughts behind WeedML which relies on XML and object-oriented systems development. Proof-of-concept software is provided as open-source C++ code and executables that can be downloaded freely.
Tipo: Journal paper Palavras-chave: Systems research and participatory research Education; Extension and communication.
Ano: 2010 URL: http://orgprints.org/18814/4/18814.pdf
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