An eco‐physiological model for interspecific competition, applied to the influence of Chenopodium album L. on sugar beet. II. Model evaluation

Abstract

Summary: Résumé: Zusammenfassung A simulation model for crop‐weed competition, parameterized for sugar beet and Chenopodium album L., was validated with experimental data from five field experiments. Between the experiments, 98% of the variation in yield loss, ranging from –6 to 96%, was explained by the simulation model. After validation, the model was used to analyse the backgrounds of the distinct differences in yield loss between the experiments. The contribution of differences in water shortage appeared to be negligible. The number of days between crop and weed emergence, which ranged from 0–31 days, appeared to be the main factor responsible for the differences in yield loss between the experiments (96%). Further analysis showed that water shortage only influences competitive strength of the weeds when overtopped by the crop. Temperature in the period between crop and weed emergence appeared to be an important factor determining the competitive relationships. It is concluded that the period between crop and weed emergence should be expressed as a developmental measure (i.e. degree days) instead of days. Morphological characteristics such as the relative growth rate of leaf area in early growth phases, specific leaf area and height increase largely determined the competitive strength of a species. The effect of physiological characteristics, such as maximum rate of leaf photosynthesis, was less significant. Un modèle écophysiologique pour la compétition interspécifique appliquéà l'influence de Chenopodium album L. sur la betterave sucrière II. Evaluation du modèle Un modèle de simulation de la compétition culture/adventice, paramétré pour la betterave et Chenopodium album L. a été validé avec des données expérimentales issues de 5 essais de plein champ. Entre les essais, 98% de la variation de perte de rendement, allant de – 6 à 96%étaient expliqués par le modèle de simulation. Après validation, le modèle a été utilisé pour analyser les courbes des différences de pertes de rendement entre les essais. Les différences liées au manque d'eau sont négligeables. Le nombre de jour entre la levée de la culture et de l'adventice qui a varié de 0 à 31 jours, est apparu être le principal facteur responsable des différences entre perte de rendement entre les essais (96%). D'autres analyses ont montré que le manque d'eau influence seulement la vigueur de compétition des adventices quand elles sont recouvertes par la culture. La température de la période entre la levée de la culture et de l'adventice apparaît être un important facteur déterminant les relations de compétition. II estconclu que la période entre la levée de la culture et de l'adventice devrait être exprimée en mesure de développement (par exemple en degrés/jour plutôt qu'en jour). Des caractéristiques morphologiques comme le taux de croissance relative de la surface foliaire dans les premiers stades, la surface spécifique foliaire et l'augmentation de hauteur, déterminent grandement la vigueur de compétition d'une espèce. Les effets des caractéristiques phy...

Modelling assimilation rates of 14 temperate arable weed species as a function of the environment and leaf traits

“…Assimilate is converted to additional biomass and allocated to different plant structures (after losses to maintenance and growth respiration have been deducted) using partitioning functions. The proportion of available resource captured by each competing species is determined by their eco‐physiological traits, especially early seedling growth rate and plant height (Kropff et al. , 1992).…”

Dry matter production and partitioning of Chenopodium album in contrasting competitive environments

“…Chenopodium album L. has previously been used as a competitor with sugar beet in a mechanistic crop:weed model (Kropff & Spitters, 1992a,b). The photosynthetic characteristics of C. album were repeatedly measured in controlled environments, but the wide range of gas exchange rates do not follow a common general trend.…”

Competitive relationships between sugar beet and weeds in dependence on time of weed control

“…Duration of that period is most often related to the sum of effective temperatures of the crop (Dunan et al 1996, Ferrero et al 1996, Martinková and Honěk 2001 or to the crop growth stage (Chykoye et al 1995). For example, Kropff et al (1992) made an ecophysiologigal model for an effect of competition of Chenopodum album on sugar beet -the main factor for reduced yield loss of sugar beet was an emergence timing of weeds compared to crop. The weeds, whose emergence before sprouting of crop is more competitive, can cause higher yield loss in low weed intensity.…”