Estimation of Spring Wheat Leaf Growth Rates and Anthesis from Air Temperature1
- Armand Bauer,
- A. B. Frank and
- A. L. Black2
Seasonal variability in climate within and between the major spring wheat (Triticum aestivum L.) growing regions of the world causes large differences in plant development patterns. A major need of models attempting to describe crop growth as a dynamic process is an evaluation of phenological development. Researchers modeling growth and yield would benefit from a meteorologically-based phenological index that accurately and reliably predicts the development stage. The objective of this study was to develop capability to estimate leaf growth rate and crop growth stage from planting to anthesis under variable management and climatic conditions. Aboveground morphological entities of 16 hard red spring (HRS) and 3 durum (T. durum Desf.) wheats were rated in Haun scale designations in seven field trials grown on Williams loam (fine-loamy, mixed Typic Ar-giboroll). These designations were regressed with growing degree-days (GDD), photothermal units (PTU), and days (DAYS) after emergence. Time to emergence did not differ among cultivars within a trial. Among the seven trials, emergence occurred 7 to 15 days after planting; accumulated GDD ranged from 94 to 138, and averaged 106. Eighteen of the cultivars produced eight leaves, ‘James’ produced seven. Main-stem phyllochron interval was 73 GDD for the HRS cvs. Butte and Waldron combined for analysis, and about 81 GDD for either “other” eight-leaved HRS cultivars or for the durums combined for analysis, and for James. The R2 value for any combined analysis was no less than 0.970**, significant at the 0.01 level. Soil water level and fertilizer N rate had no effect on main stem development rate, but did affect the maximum number of tillers produced per plant. The GDD accumulated per plant growth unit from emergence to anthesis (leaves plus four stages after expansion of the flag leaf) was the same as from emergence through full expansion of the flag leaf. Precision of estimating growth rates and stages with GDD was the same as with PTU, and both were superior to DAYS.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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