Level II Agricultural
Business Operations
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Scale proposed by the Dutch
phytopathologist, Jan C. Zadoks
Know as Zadoks scale, it gives the plant a
figure based on the current growth stage of
the plant.
Scales goes from 00-99.
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Knowing the stages of development of a crop
is critical in many management decisions that
growers make.
Eg,
Nitrogen application
Herbicide application
Fungicide application
Growth regulator
GS21
GS11
GS32
GS32
Slow
N Uptake (kg/ha)
250
Rapid
Slow
Harvest
200
GS 61
150
GS 39
40 % of total N
uptake in 4 weeks
100
50
GS 31
17 % of total N uptake
0
Feb
Mar
Apr
May
Jun
Jul
Aug
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T1, T2 & T3 are linked to timing of fungicide
spraying.
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T1 is generally GS 32-33
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T2 is GS 39
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T3 is a ear wash at GS 65
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Some other T values have been developing e.g.
T0.5, T1.5 etc. Becoming more popular in NI
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Link from HGCA website.
http://www.hgca.com/media/180128/g49cereals-growth-stages-a-guide-for-croptreatments.pdf
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Seedling Growth
Tillering
Stem Elongation
Booting
Ear Emergence
Flowering
Milk Development
Dough Development
Ripening
11-19
20-29
30-39
41-49
51-59
61-69
71-79
81-89
91-99
GS10 First leaf through coleoptile
GS11 First leaf unfolded (ligule visible)
GS13 - 3 leaves unfolded
GS15 - 5 leaves unfolded
GS19 - 9 or more leaves unfolded
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GS20 Main shoot only
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GS21 Main shoot and 1 tiller
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GS23 Main shoot and 3 tillers
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GS25 Main shoot and 5 tillers
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GS29 Main shoot and 9 or more tillers
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GS30 Ear at 1cm (pseudostem erect)
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GS31 First node detectable
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GS32 Second node detectable
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GS33 Third node detectable
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GS37 Flag leaf just visible
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GS39 Flag leaf blade all visible
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Very Important Period
◦ Fungicide Timing
◦ Growth regulator
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For a quick, but crude assessment, fold back
the leaf sheaths then count the slight 'bumps'
caused by each node.
The exact stage is revealed by stripping off
leaves and cutting the main stem
longitudinally with a sharp knife.
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GS41 Flag leaf sheath extending
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GS43 Flag leaf sheath just visibly swollen
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GS45 Flag leaf sheath swollen
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GS47 Flag leaf sheath opening
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GS49 First awns visible (if an awned variety)
Barley only
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GS51 First spikelet of ear just visible above
flag leaf ligule
GS55 Half of ear emerged above flag leaf
ligule
GS59 Ear completely emerged above flag leaf
ligule
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GS61 Start of flowering
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GS65 Flowering half-way
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GS69 Flowering complete
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GS71 Grain watery ripe
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GS73 Early milk
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GS75 Medium milk
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GS77 Late milk
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GS83 Early dough
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GS85 Soft dough
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GS87 Hard dough (thumbnail impression
held)
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GS91 Grain hard (difficult to divide)
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GS92 Grain hard (not dented by thumbnail)
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GS93 Grain loosening in daytime
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Correct timing of sprays and fertiliser
treatments is critical to success in growing
cereals.
Many instructions and guides state ‘Apply at
GSXX.”
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Take 5-10 typical plants from across the
field, ideally digging them up rather than
pulling up to avoid damaging stems and
leaves.
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Knowing the growth stage is important to
ensure that timing of pesticides are applied in
line with manufactures recommendations.
Correct timing can have a bigger impact on
crop response/performance than product
type!