Common Sunflower Seedling Emergence across the U.S. Midwest

Authors

• Sharon A. Clay, South Dakota State University
• Adam Davis, USDA Agricultural Research Service, Urbana, Illinois
• Anita Dille, Kansas State UniversityFollow
• John Lindquist, University of Nebraska-LincolnFollow
• Analiza H. M. Ramirez, Kansas State University
• Christy Sprague, Michigan State UniversityFollow
• Graig Reicks, South Dakota State University
• Frank Forcella, USDA Agricultural Research Service, Morris, Minnesota

Document Type

Article

Date of this Version

2014

Citation

Weed Science 62 (2014): 63–70

doi: 10.1614/WS-D-13-00078.1

Comments

U.S. government work. Public domain

Abstract

Predictions of weed emergence can be used by practitioners to schedule POST weed management operations. Common sunflower seed from Kansas was used at six Midwestern U.S. sites to examine the variability that 16 climates had on common sunflower emergence. Nonlinear mixed effects models, using a flexible sigmoidal Weibull function that included thermal time, hydrothermal time, and a modified hydrothermal time (with accumulation starting from January 1 of each year), were developed to describe the emergence data. An iterative method was used to select an optimal base temperature (T_b) and base and ceiling soil matric potentials (ψ_b and ψ_c) that resulted in a best-fit regional model. The most parsimonious model, based on Akaike’s information criterion (AIC), resulted when T_b = 4.4 C, and ψ_b = –20000 kPa. Deviations among model fits for individual site years indicated a negative relationship (r = –0.75; P < 0.001) between the duration of seedling emergence and growing degree days (T_b = 10 C) from October (fall planting) to March. Thus, seeds exposed to warmer conditions from fall burial to spring emergence had longer emergence periods.