Wheat growth stages on this website are modeled using growing degree days. The
formula for wheat growing degree days is:
GDD = 0.5 x (Tmax + Tmin) - 32
where maximum or minimum temperatures are capped at 32 F on the low end, and
70 F or 95 F on the high end before and after the crop has reached the 2nd
leaf stage. Growing degree days for the season to date are drawn from
high-resolution weather analyses provided by Meridian Environmental
Technology, Inc. These analyses combine observations from various surface
observation networks and remote sensing platforms (e.g., radar and satellite)
to arrive at best-guess estimates of the weather each field has been exposed
to.
The growing degree day (GDD) to growth stage mapping used for early maturity
wheat on this website is provided by Dr. Charla Hollingsworth of the
University of Minnesota Extension Service, and is shown in the following
table:
|
Plant Growth Stage Description
|
Required GDD
|
|
Planting to Emergence
|
80 + 50/in of depth
|
|
Emergence
|
0
|
|
First leaf emerged
|
72
|
|
Second leaf emerged, tillering is initiated
|
215
|
|
Third leaf emerged
|
358
|
|
Fourth leaf emerged, tillers visible
|
501
|
|
Fifth leaf emerged, tillering ends
|
644
|
|
Sixth leaf emerged, stem extension begins
|
715
|
|
Seventh leaf emerged, stem extension continues
|
895
|
|
Eighth leaf (flag leaf) emerging, stem extension continues
|
1,001
|
|
Flag leaf emerged, stem extension continues
|
1,075
|
|
Boot swollen, awns within stem at flag leaf height
|
1359
|
|
Awns emerging
|
1430
|
|
Head fully emerged, stem extension continues
|
1502
|
|
Flowering begins, stem extension ends
|
1590
|
|
Flowering complete, kernel development begins
|
1616
|
|
Kernel watery ripe, kernel development continues
|
1673
|
|
Hard dough, kernel development ends
|
2070
|
Dr. Jochum Wiersma at the University of Minnesota Croookston has provided
adjustments to these GDD requirements for other maturity classes, and has also
provided maturity classifications for varieties of spring wheat commonly grown
in Minnesota. The adjustments are in the form of a multiplicative factors for
the GDD requirements listed in the table above.
|
Variety
|
Maturity
|
Adjustment Factor
|
|
Ingot
|
Early
|
1.00
|
|
Briggs
|
Early
|
1.00
|
|
Oklee
|
Early
|
1.00
|
|
Walworth
|
Early
|
1.00
|
|
Dapps
|
Early
|
1.00
|
|
Oxen
|
Early
|
1.00
|
|
Alsen
|
Medium Early
|
1.02
|
|
Reeder
|
Medium Early
|
1.02
|
|
Knudson
|
Medium Early
|
1.02
|
|
Mercury
|
Medium Early
|
1.02
|
|
Parshall
|
Medium Early
|
1.02
|
|
Russ
|
Medium Early
|
1.02
|
|
Hanna
|
Medium Early
|
1.02
|
|
2375
|
Medium
|
1.04
|
|
Dandy
|
Medium
|
1.04
|
|
HJ98
|
Medium
|
1.04
|
|
Ivan
|
Medium
|
1.04
|
|
Lars
|
Medium
|
1.04
|
|
Verde
|
Medium Late
|
1.06
|
|
NorPro
|
Medium Late
|
1.06
|
|
Gunner
|
Medium Late
|
1.06
|
|
Granite
|
Late
|
1.075
|
|
Ivan
|
Late
|
1.075
|
|
Marshall
|
Late
|
1.075
|
If you find that a variety of wheat you have in production is not listed in
the pull-down variety selection menu, generic maturity-based selections are
available.
Growth projections for dates in the future are based upon a combination of
observed GDDs for days that have already past and climatological temperatures
for days in the future. Errors in the growth model as well as deviations of
the weather from climatological normals may cause these projections to be in
error. Please use this tool only as a rough guide to growth staging and
monitor your own fields for more precise growth stage information during
critical growth periods.
References:
Bauer, A. A.B. Frank, and A.L. Black. Estimation of spring wheat leaf growth
rates and anthesis from air temperature. Agron. J. 76:829-835.
Haun, J.R. 1973. Visual quantification of wheat development. Agron. J.
65:116-119.
Large, E.C. 1954. Growth stages in cereals. Plant Pathol. 3:128-129.
Nelson, J.E., K.D. Kephart, A. Bauer, and J.F. Connor. 1988. Growth Staging
Wheat, Barley, and Wild Oat. American Cyanamid Co., Reprint by NDSU Extension
Service.
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