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| Nkurunziza, Libère; Andreasen, Christian; Liu, Fulai; Streibig, Jens Carl. |
| The aim of this study was to investigate the effect of controlled soil water deficits on sprouting and shoot growth of Canada thistle, coltsfoots and quackgrass. A gradient of soil water contents was created by establishing different densities of barley. The plants were harvested 14 days after watering was stopped. On Canada thistle and coltsfoots, relative water content (RWC) in leaves was measured prior to harvest and biomass of all weed shoots were recorded at harvest. In terms of shoot biomass and leaf RWC quackgrass was drought tolerant while coltsfoot was drought sensitive and Canada thistle was between the two. The barley cover crop could have had a competitive effect upon the growth of the weeds; the effect, however, was not detrimental compared to... |
| Tipo: Journal paper |
Palavras-chave: Weed management. |
| Ano: 2011 |
URL: http://orgprints.org/18363/1/Nkurunziza_Drought_Perennial_3.pdf |
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| Nkurunziza, Libère. |
| Perennial weed infestations are putting severe constraints on organic and conventional farming. Cirsium arvense (L.) Scop. and Tussilago farfara L. have high vegetative regeneration capacity from underground organs. These organs can reach deep soil layers, which prevent them from being easily uprooted. In our research, we primarily addressed the importance of the source-sink dynamics of carbohydrates at different phenological stages and related results to eventual management strategies. Experimental work was carried out under greenhouse and/or growth chamber conditions. The first study spanned from roots/rhizomes planting to shoot establishment. The second study began after establishment and included the rosette to the flowering stages. The third study... |
| Tipo: Thesis |
Palavras-chave: Farming Systems; Food systems. |
| Ano: 2010 |
URL: http://orgprints.org/18240/1/18240.pdf |
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| Nkurunziza, Libère; Streibig, Jens Carl. |
| The information of the source-sink dynamics of carbohydrates during early growth can indicate when perennial weeds are most vulnerable to mechanical control. In this study, carbohydrate contents in the roots or rhizomes of two noxious perennial weeds, Cirsium arvense and Tussilago farfara, and basipetal translocation of photo-assimilates were measured. We used HPLC for carbohydrate measurements and 14C labelling to follow the translocation of photo-assimilates during the early growth. These measurements were related to leaf number and leaf area. Fructan and fructose changed significantly over the experimental periods. Fructan for both species was greatest within two weeks after planting 5-cm long root/rhizome fragments and declined thereafter. After two... |
| Tipo: Journal paper |
Palavras-chave: Weed management. |
| Ano: 2010 |
URL: http://orgprints.org/18360/1/Nkurunziza_Cirsium_Tussilago_2.pdf |
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| Nkurunziza, Libère; Rosenqvist, Eva; Streibig, Jens Carl. |
| Cirsium arvense and Tussilago farfara are noxious creeping perennial weeds of temperate crops. Cirsium arvense infests both conventional and organic crops, while T. farfara is more common in organic cropping systems. Mechanical control used in organic farming often leaves intact shoots within crop rows. It is unknown whether shoots and rhizomes are affected by cutting adjacent interconnected shoots. In glasshouse experiments, comparison of net photosynthesis, chlorophyll a fluorescence and quantum efficiency (Fv/Fm) of disturbed and undisturbed clones, did not show any disturbance effect. Maximum net photosynthesis decreased over time in both disturbed and undisturbed clones, depending on environmental conditions. Maximum net photosynthesis was not... |
| Tipo: Journal paper |
Palavras-chave: "Organics" in general; Farming Systems. |
| Ano: 2010 |
URL: http://orgprints.org/18238/1/18238.pdf |
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| Nkurunziza, Libère; Streibig, Jens Carl. |
| Carbohydrate storage in underground organs of perennial weeds will increase because of the increasing temperatures and CO2 concentrations that increase photosynthesis. The objective of this study was to understand the effects of temperature and shoot age on the storage of fructan, the main carbohydrate storage, and the depletion associated with regeneration during the early growth. We subjected juvenile and mature plants of Canada thistle and Coltsfoot to different temperatures, in growth chambers, and we measured fructan in roots/rhizomes. After temperature treatment, roots/rhizomes were replanted to assess their regenerative ability. Juvenile plants subjected to lower temperatures did not store fructan. While Canada thistle showed higher fructan storage... |
| Tipo: Working paper |
Palavras-chave: Weed management. |
| Ano: 2011 |
URL: http://orgprints.org/18364/1/Nkurunziza_Cirsium_Tussilago_fructan_4.pdf |
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