http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Modeling the emergence of seedling johnsongrass [Sorghum halepense (L.) Pers.]
Research was conducted to investigate the influence of burial
depth and temperature on seedling johnsongrass emergence and
to use the generated data in the formulation of predictive
models. Constant temperature growth chamber experiments
indicated that there was a significant interaction between
burial depth and temperature. Percent emergence and time to
first emergence were highly dependent upon this interaction
and needed to be evaluated on an individual basis.
Generally, emergence ranged between 0 and 54 % while time to
first emergence ranged between 3 and 19 days. The constant
temperature-burial depth data and previously published
emergence data were used to formulate an emergence model
using the Fermi-Dirac distribution function. The Fermi-Dirac
distribution function was found to be an adequate model for
describing seedling emergence, as influenced by burial depth,
of various weed species including johnsongrass, downy brome,
and round-leaf mallow. Model adequacy was determined by a
good visual fit of the model to the data, narrow confidence
intervals for the model parameters, and an appropriate
regression analysis of the modeled vs. an independent
observed data set. The poikilotherm rate equation was fit to
the seedling emergence data that was generated from 0 to 2.5
cm burial depths. The equations developed from this data
were combined to form a fourparameter poikilotherm rate
equation that could be used to model the emergence of
seedling johnsongrass from these depths at any constant
temperature between 20 and 44 C. When this single
poikilotherm rate equation model was validated against
independent emergence data, a good visual fit of the model to
the data and an appropriate regression analysis of the
Issued also on microfiche from University Microfilms Inc.
Includes bibliographical references: pages 67-71.