The use of thermal time to model common lambsquarters (Chenopodium album) seedling emergence in corn

Abstract

A mathematical model was developed to predict common lambsquarters seedling emergence in southwestern Quebec. The model was based on the thermal-time concept, using air temperatures in the double-sine calculation method. The model was built using data from five experiment-years for corn naturally infested with weed populations. Once developed, the model was calibrated using different crop seedbed preparation times. The base temperature was then adjusted for each time of seedbed preparation. A power regression function was used to relate adjusted base temperatures and the accumulated thermal units at seedbed preparation time. A modified Weibull function was then fitted to the field emergence data, expressed as the cumulative proportion of the total seedling emergence over the growing season as a function of cumulative thermal units. The simplicity and accuracy of this model would make it an excellent tool to predict common lambsquarters seedling emergence in field situations, facilitating the determination of the timing of scouting in integrated weed management systems.

Temperatura cardeal e potencial hídrico na germinação de sementes de corda-de-viola (Ipomoea triloba)

“…Os parâmetros k, a e c foram estimados por um procedimento de regressão não-linear, usando o método DUD (Doesn't Use Derivative) de computação (Ralston & Jennrich, 1979). Esse é um método de regressão não-linear que usa o método iterativo multivariado secante para estimar os parâmetros de interesse (Bahler et al, 1989).…”

“…Os parâmetros k, a e c foram estimados por um procedimento de regressão não-linear, usando o método DUD (Doesn't Use Derivative) de computação (Ralston & Jennrich, 1979), plotando o tempo hidrotérmico versus porcentagem de germinação.…”

“…A resposta à temperatura foi classificada e resumida em três temperaturas cardeais: mínima, ótima e máxima (Grundy & Mead, 2000;Alvarado & Bradford, 2002;Leblanc et al, 2003).…”

Short communication: Evaluation of a model for predicting Avena fatua and Descurainia sophia seed emergence in winter rapeseed

“…The cumulative soil thermal time (CTT) was estimated daily during the growing season with the following equation (Leblanc et al, 2003;Leguizamon et al, 2005;Izquierdo et al, 2013):…”

Using thermal and hydrothermal time to model seedling emergence of Avena sterilis ssp. ludoviciana in Spain

“…Daily soil temperature and water content were used to calculate accumulated thermal ( Θ T ) and hydrothermal ( Θ H ) time under a range of different base temperatures and base water potentials ( T b and Ψ b , respectively). Although several methods for calculating thermal time have been proposed, we used the mean‐minus‐base method (Leblanc et al. , 2003): where Θ T represents the thermal time to seedling emergence (in growing degree days), i is the starting date to cumulate degree days, n is the time required to complete emergence, T max and T min are the daily maximum and minimum temperatures and T b is the base temperature for emergence.…”