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| Registros recuperados: 19 | |
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| 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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| 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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| 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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| 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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| 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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| 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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| 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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| 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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| 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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| Registros recuperados: 19 | |
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