Clarence Swanton - Academia.edu (original) (raw)
Papers by Clarence Swanton
Weed ecology in natural and agricultural systems
Weed ecology in natural and agricultural systems
Weed ecology in natural and agricultural systems
Weed ecology in natural and agricultural systems, 2003
This chapter describes commonly used methods and procedures for sampling population abundance, co... more This chapter describes commonly used methods and procedures for sampling population abundance, constructing survival curves, and designing population interaction (competition and herbivory) experiments.
Invasive plant ecology in natural and agricultural systems, 2010
This chapter addresses aspects of community structure and of diversity (the number and relative a... more This chapter addresses aspects of community structure and of diversity (the number and relative abundances of species present in a community), specifically in a meadow. The discusses how to define and describe communities, and then discuss patterns, causes and consequences of diversity.
Weed ecology in natural and agricultural systems, 2003
This chapter discusses the process and impact of plant invasion, and describes invasion success a... more This chapter discusses the process and impact of plant invasion, and describes invasion success as a function of the invasive ability of species and habitat invasibility.
Weed ecology in natural and agricultural systems
Integrated weed management for sustainable agriculture
In order to intensify agricultural productivity while at the same time enhance ecosystem services... more In order to intensify agricultural productivity while at the same time enhance ecosystem services, it is necessary to evaluate carefully how current weed-management technologies are deployed, including herbicides and herbicide-resistant crops. Herbicide chemistries and herbicide-resistant crops have provided excellent technologies that have resulted in significant changes to the way weeds can be controlled. This chapter highlights several key components that must form the basis for an effective integrated weed-management strategy, including tillage, the importance of understanding weed emergence relative to the crop, critical periods for weed control, crop morphology, row width, nutrient management and crop rotation.
Applied and Environmental Microbiology, 2007
We grew plants of nine soybean varieties, six of which were genetically modified to express trans... more We grew plants of nine soybean varieties, six of which were genetically modified to express transgenic cp4-epsps , in the presence of Bradyrhizobium japonicum and arbuscular mycorrhizal fungi. Mycorrhizal colonization and nodule abundance and mass differed among soybean varieties; however, in no case was variation significantly associated with the genetic modification.
Canadian Journal of Soil Science, 2000
In corn (Zea mays L.) – soybean [Glycine max (L.) Merr.] – winter wheat (Triticum aestivum L.) ro... more In corn (Zea mays L.) – soybean [Glycine max (L.) Merr.] – winter wheat (Triticum aestivum L.) rotations cultivated in sandy soil under three tillage systems, with and without cover cropping, the soil wind-erodible fraction (<0.85 mm) ranged from 78 to 96%. Proportion and wet-aggregate stability (WAS) of the 0.85- to 5.7-mm fraction both ranked no-till (8.1% of total soil weight and 49% water-stable) > chisel plow (6.7 and 39%) > conventional plow (5.3 and 35%). Cover cropping had little effect on dry aggregate size distribution or WAS. Key words: Zea mays, Secalecereale, soil structure, aggregate stability, cover crop, tillage
Weed Technology, 2009
Thirteen field experiments were conducted in Illinois, Indiana, Ohio, and Ontario from 2005 to 20... more Thirteen field experiments were conducted in Illinois, Indiana, Ohio, and Ontario from 2005 to 2007 to determine the effects of simulated glyphosate drift followed by in-crop applications of nicosulfuron/rimsulfuron plus dicamba/diflufenzopyr or foramsulfuron plus bromoxynil plus atrazine on nontransgenic corn injury, height, stand count, shoot dry weight, and yield. Simulated glyphosate drift at 100 and 200 g/ha, resulted in 11 to 61% visual crop injury and a 19 to 45% decrease in corn height. Simulated glyphosate drift at 200 g/ha caused a reduction in shoot dry weight by 46%, stand count by 28% and yield by 49 to 56%. Generally, simulated glyphosate drift followed by the in-crop herbicides resulted in an additive response with respect to visual crop injury, height, stand count, shoot dry weight, and yield.
Weed research (Print), 1995
The performance of three empirical models describing white bean yield loss (YL) from common ragwe... more The performance of three empirical models describing white bean yield loss (YL) from common ragweed competition was compared using field experiments from Staffa and Woodstock, both in Ontario, Canada, in 1991 and 1992. One model was based upon both weed density and relative time of emergence. The other two models described yield loss as a function of weed leaf area relative to the crop. The model based on both weed density and relative time of emergence best described the data sets. The predicted maximum yield loss (A) and the parameter for relative time of weed emergence (C) varied across locations and years whereas the yield loss at low weed density (/) was relatively more consistent across locations and years. Use of thermal time (base temperature=10°C) rather than calendar days did not change the overall fit of the model, but reduced the value of the parameter for the relative time of weed emergence (C). The two parameter leaf area model accounting for maximum yield loss (m) gave a better fit to the data compared with the one parameter model. The relative damage coefficient (q) varied with time of leaf area assessment, location and year. Values of q calculated from relative leaf area growth rates of the crop and weed were similar to observed values.
Weed research (Print), 1994
Grundlagen fUr die selektive Wirkung von Fluroxypyr Die Dosis/Wirkungs-Beziehung, Blattaufnahme, ... more Grundlagen fUr die selektive Wirkung von Fluroxypyr Die Dosis/Wirkungs-Beziehung, Blattaufnahme, Translokation und Metabolismus des Methylheptyl-Esters (MHE) von Fluroxypyr wurden bei WeiBem GansefuB {Chenopodium album L.), Gemeinem Windenknoterich {Folygonum convolvulus L.), Acker-Kratzdistel {Cirsium arvense (L.) Scop.) und Gemeiner Ackerwinde {Convolvulus arvensis L.) untersucht. Unter den kontrollierten Umweltbedingungen eines Phytotrons wurden anhand des Trockengewichts die EDso-Werte bestimmt, die bei den empfindlichen Arten Folygonum convolvulus mit 16 g ha~' und Convolvulus arvensis mit 40 g ha"' sich deutlich von denen der toleranten Arten Chenopodium album mit 331 g ha"' und Cirsium arvense mit s800 g ha"' unterschieden. Unabhangig von der Art waren mehr als 80 % der Aufwandmenge von ['''C]-Fluroxypyr-MHE durch die Blattoberflachen 120 h nach der Behandlung aufgenommen. Die Translokation der Radioaktivitat aus den behandelten Blattern war bei den empfindlichen Arten signifikant groBer als bei den toleranten. Z. B. waren 120 h nach der Behandlung bei den toleranten Arten Cirsium arvense und Chenopodium album 15 bzw. 10 % der Radioaktivitat transloziert, wahrend es bei den empfindlichen Arten Folygonum convolvulus und Convolvulus arvensis 41 bzw. 40 % waren. Bei aUen 4 Arten ergab eine HPLC-Untersuchung der Pflanzenextrakte 4 distinkte Peaks. Bei den empfindlichen Arten wurde 120 h nach der Anwendung mit 70 % mehr Fluroxypyr wiedergefunden als bei den toleranten (30 %). Die Selektivitatsunterschiede zwischen den toleranten und empfindlichen Arten konnten auf einen beschleunigten Metabolismus des Herbizids zu starker polaren, nichphytotoxischen Stoffen mit eingeschrankter Mobilitat bei den toleranten Arten zuruckgefuhrt werden.
Weed Research, 2016
Summary Light signalling is an important mechanism of plant competition during the early stages o... more Summary Light signalling is an important mechanism of plant competition during the early stages of seedling development. Far-red-enriched (FR-E) light reflected from neighbouring weeds has been shown to induce the shade avoidance response leading to changes in plant morphology and increased variability in yields. In this study, the morphological and molecular changes occurring at the hypocotyl arch and primary leaf stage of soya bean development were investigated in response to FR-E light reflected from neighbouring weeds. A reduction in the root/shoot was identified at the hypocotyl arch stage, and an increase in height was detected at the unifoliate stage of soya bean seedlings. In addition, FR-E light induced a change in the expression profile of reactive oxygen species (ROS)-scavenging genes. Early in seedling development, ROS-scavenging genes were upregulated. However, this trend was reversed at later stages of development with downregulation of several ROS-scavenging genes. These results demonstrated the rapidity of induction of the shade avoidance response and that gene expression in soya bean seedlings was dependent upon developmental stage and tissue type sampled.
Weed ecology in natural and agricultural systems
This chapter describes the effects of competition on populations and communities; types of compet... more This chapter describes the effects of competition on populations and communities; types of competition between populations, general trends in exploitation competition and interference (such as allelopathy) competition, factors that determine the outcomes of competition, and the effects of the environment on competition, focusing mainly on interactions between weeds, and between crops and weeds.
Weed ecology in natural and agricultural systems
This chapter describes the importance of weed ecology studies to weed management using garlic mus... more This chapter describes the importance of weed ecology studies to weed management using garlic mustard (Alliaria petiolata) and dame's rocket (Hesperis matronalis) in North America, and purple nutsedge (Cyperus rotundus) in tropical and subtropical areas as examples.
Weed ecology in natural and agricultural systems
Weed ecology in natural and agricultural systems
Weed ecology in natural and agricultural systems
Weed ecology in natural and agricultural systems, 2003
This chapter describes commonly used methods and procedures for sampling population abundance, co... more This chapter describes commonly used methods and procedures for sampling population abundance, constructing survival curves, and designing population interaction (competition and herbivory) experiments.
Invasive plant ecology in natural and agricultural systems, 2010
This chapter addresses aspects of community structure and of diversity (the number and relative a... more This chapter addresses aspects of community structure and of diversity (the number and relative abundances of species present in a community), specifically in a meadow. The discusses how to define and describe communities, and then discuss patterns, causes and consequences of diversity.
Weed ecology in natural and agricultural systems, 2003
This chapter discusses the process and impact of plant invasion, and describes invasion success a... more This chapter discusses the process and impact of plant invasion, and describes invasion success as a function of the invasive ability of species and habitat invasibility.
Weed ecology in natural and agricultural systems
Integrated weed management for sustainable agriculture
In order to intensify agricultural productivity while at the same time enhance ecosystem services... more In order to intensify agricultural productivity while at the same time enhance ecosystem services, it is necessary to evaluate carefully how current weed-management technologies are deployed, including herbicides and herbicide-resistant crops. Herbicide chemistries and herbicide-resistant crops have provided excellent technologies that have resulted in significant changes to the way weeds can be controlled. This chapter highlights several key components that must form the basis for an effective integrated weed-management strategy, including tillage, the importance of understanding weed emergence relative to the crop, critical periods for weed control, crop morphology, row width, nutrient management and crop rotation.
Applied and Environmental Microbiology, 2007
We grew plants of nine soybean varieties, six of which were genetically modified to express trans... more We grew plants of nine soybean varieties, six of which were genetically modified to express transgenic cp4-epsps , in the presence of Bradyrhizobium japonicum and arbuscular mycorrhizal fungi. Mycorrhizal colonization and nodule abundance and mass differed among soybean varieties; however, in no case was variation significantly associated with the genetic modification.
Canadian Journal of Soil Science, 2000
In corn (Zea mays L.) – soybean [Glycine max (L.) Merr.] – winter wheat (Triticum aestivum L.) ro... more In corn (Zea mays L.) – soybean [Glycine max (L.) Merr.] – winter wheat (Triticum aestivum L.) rotations cultivated in sandy soil under three tillage systems, with and without cover cropping, the soil wind-erodible fraction (<0.85 mm) ranged from 78 to 96%. Proportion and wet-aggregate stability (WAS) of the 0.85- to 5.7-mm fraction both ranked no-till (8.1% of total soil weight and 49% water-stable) > chisel plow (6.7 and 39%) > conventional plow (5.3 and 35%). Cover cropping had little effect on dry aggregate size distribution or WAS. Key words: Zea mays, Secalecereale, soil structure, aggregate stability, cover crop, tillage
Weed Technology, 2009
Thirteen field experiments were conducted in Illinois, Indiana, Ohio, and Ontario from 2005 to 20... more Thirteen field experiments were conducted in Illinois, Indiana, Ohio, and Ontario from 2005 to 2007 to determine the effects of simulated glyphosate drift followed by in-crop applications of nicosulfuron/rimsulfuron plus dicamba/diflufenzopyr or foramsulfuron plus bromoxynil plus atrazine on nontransgenic corn injury, height, stand count, shoot dry weight, and yield. Simulated glyphosate drift at 100 and 200 g/ha, resulted in 11 to 61% visual crop injury and a 19 to 45% decrease in corn height. Simulated glyphosate drift at 200 g/ha caused a reduction in shoot dry weight by 46%, stand count by 28% and yield by 49 to 56%. Generally, simulated glyphosate drift followed by the in-crop herbicides resulted in an additive response with respect to visual crop injury, height, stand count, shoot dry weight, and yield.
Weed research (Print), 1995
The performance of three empirical models describing white bean yield loss (YL) from common ragwe... more The performance of three empirical models describing white bean yield loss (YL) from common ragweed competition was compared using field experiments from Staffa and Woodstock, both in Ontario, Canada, in 1991 and 1992. One model was based upon both weed density and relative time of emergence. The other two models described yield loss as a function of weed leaf area relative to the crop. The model based on both weed density and relative time of emergence best described the data sets. The predicted maximum yield loss (A) and the parameter for relative time of weed emergence (C) varied across locations and years whereas the yield loss at low weed density (/) was relatively more consistent across locations and years. Use of thermal time (base temperature=10°C) rather than calendar days did not change the overall fit of the model, but reduced the value of the parameter for the relative time of weed emergence (C). The two parameter leaf area model accounting for maximum yield loss (m) gave a better fit to the data compared with the one parameter model. The relative damage coefficient (q) varied with time of leaf area assessment, location and year. Values of q calculated from relative leaf area growth rates of the crop and weed were similar to observed values.
Weed research (Print), 1994
Grundlagen fUr die selektive Wirkung von Fluroxypyr Die Dosis/Wirkungs-Beziehung, Blattaufnahme, ... more Grundlagen fUr die selektive Wirkung von Fluroxypyr Die Dosis/Wirkungs-Beziehung, Blattaufnahme, Translokation und Metabolismus des Methylheptyl-Esters (MHE) von Fluroxypyr wurden bei WeiBem GansefuB {Chenopodium album L.), Gemeinem Windenknoterich {Folygonum convolvulus L.), Acker-Kratzdistel {Cirsium arvense (L.) Scop.) und Gemeiner Ackerwinde {Convolvulus arvensis L.) untersucht. Unter den kontrollierten Umweltbedingungen eines Phytotrons wurden anhand des Trockengewichts die EDso-Werte bestimmt, die bei den empfindlichen Arten Folygonum convolvulus mit 16 g ha~' und Convolvulus arvensis mit 40 g ha"' sich deutlich von denen der toleranten Arten Chenopodium album mit 331 g ha"' und Cirsium arvense mit s800 g ha"' unterschieden. Unabhangig von der Art waren mehr als 80 % der Aufwandmenge von ['''C]-Fluroxypyr-MHE durch die Blattoberflachen 120 h nach der Behandlung aufgenommen. Die Translokation der Radioaktivitat aus den behandelten Blattern war bei den empfindlichen Arten signifikant groBer als bei den toleranten. Z. B. waren 120 h nach der Behandlung bei den toleranten Arten Cirsium arvense und Chenopodium album 15 bzw. 10 % der Radioaktivitat transloziert, wahrend es bei den empfindlichen Arten Folygonum convolvulus und Convolvulus arvensis 41 bzw. 40 % waren. Bei aUen 4 Arten ergab eine HPLC-Untersuchung der Pflanzenextrakte 4 distinkte Peaks. Bei den empfindlichen Arten wurde 120 h nach der Anwendung mit 70 % mehr Fluroxypyr wiedergefunden als bei den toleranten (30 %). Die Selektivitatsunterschiede zwischen den toleranten und empfindlichen Arten konnten auf einen beschleunigten Metabolismus des Herbizids zu starker polaren, nichphytotoxischen Stoffen mit eingeschrankter Mobilitat bei den toleranten Arten zuruckgefuhrt werden.
Weed Research, 2016
Summary Light signalling is an important mechanism of plant competition during the early stages o... more Summary Light signalling is an important mechanism of plant competition during the early stages of seedling development. Far-red-enriched (FR-E) light reflected from neighbouring weeds has been shown to induce the shade avoidance response leading to changes in plant morphology and increased variability in yields. In this study, the morphological and molecular changes occurring at the hypocotyl arch and primary leaf stage of soya bean development were investigated in response to FR-E light reflected from neighbouring weeds. A reduction in the root/shoot was identified at the hypocotyl arch stage, and an increase in height was detected at the unifoliate stage of soya bean seedlings. In addition, FR-E light induced a change in the expression profile of reactive oxygen species (ROS)-scavenging genes. Early in seedling development, ROS-scavenging genes were upregulated. However, this trend was reversed at later stages of development with downregulation of several ROS-scavenging genes. These results demonstrated the rapidity of induction of the shade avoidance response and that gene expression in soya bean seedlings was dependent upon developmental stage and tissue type sampled.
Weed ecology in natural and agricultural systems
This chapter describes the effects of competition on populations and communities; types of compet... more This chapter describes the effects of competition on populations and communities; types of competition between populations, general trends in exploitation competition and interference (such as allelopathy) competition, factors that determine the outcomes of competition, and the effects of the environment on competition, focusing mainly on interactions between weeds, and between crops and weeds.
Weed ecology in natural and agricultural systems
This chapter describes the importance of weed ecology studies to weed management using garlic mus... more This chapter describes the importance of weed ecology studies to weed management using garlic mustard (Alliaria petiolata) and dame's rocket (Hesperis matronalis) in North America, and purple nutsedge (Cyperus rotundus) in tropical and subtropical areas as examples.