Auniformdecimalcodeforgrowthstagesofcropsandweeds

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A uniform decimal code for growth stages of crops and weeds
ArticleinAnnals of Applied Biology · February 2008
DOI: 10.1111/j.1744-7348.1991.tb04895.x
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Am. appl. Biot. (1991), 119, 561-601
Primed in Great Britain 561
A uniform decimal code for growth stages of crops and weeds
By PETER D. LANCASHIRE', H. BLEIHOLDER^, T. VAN DEN BOOM^,
P. LANGELÜDDEKE'*, R. STAUSS^, ELFRIEDE WEBERN and A. WITZENBERGER'
^ Bayer UK Limited, Crop Protection Business Group, Eastern Way, Bury St Edmunds, Suffolk
IP32 7AH, UK
^BASF AG, Landwirtschaftliche Versuchsstation, Postfach 220, 6703 Limburgerhof,
West Germany
^Bayer AG, Biologische Entwicklung, Pflanzenschutzzentrum-Monheim, 5090 Leverkusen,
West Germany
^Hoechst AG, Pflanzenschutz-Forschung, Freilandversuchswesen, Hessendamm 1-3,
6234 Hattersheim, West Germany
^Ciba-Geigy AG, Division Agro, 4002 Basel, Switzerland
(Accepted 30 September 1991)
Summary
A universal scale (to be known as the BBCH scale) using a decimal code for the
description of the growth stages of most agricultural crops and weeds is proposed.
The scale and codes are based on the well-known Zadoks code for cereals.
Developmentally similar growth stages of different crops are given the same
codes. The general scale provides a framework within which more specific scales
for individual crops may be constructed. The uniformity of the scale makes it easy
to remember and use in agricultural practice and simplifies storage and retrieval in
a Computer System.
A description of the general scale is given foUowed by specific scales for cereals,
rice, maize, oilseed rape, field beans, peas and sunflower. Comparisons with
scales currently in use are given where appropriate.
Key words: Growth stage key, BBCH scale, crop, weed, Computer, cereals, wheat,
Triticum aestivum, barley, Hordeum vulgäre, oats, Avena sativa, rye,
Seeale cereale, triticale, rice, Oryza sativa, maize, Zea mays, field bean,
Vicia faba, oilseed rape, Brassica napus, pea, Pisum sativum, sunflower,
Helianthus annuus
Introduction
All who work with agricultural crops need to describe the growth stages ofthose crops in an
unambiguous and readily-understood way. The use of a Standard scale describing important
growth stages is the usual solution. Many Standard descriptions of growth stages are
available, particularly for economically-important crops: Landes & Porter (1989) describe and
compare 23 scales for temperate cereals. However, for many minor crops no Standard
description of their growth stages exists and the scales used for other crops are usually too
specific to adapt.
Currently used scales for the same crop often distinguish diff'erent growth stages. Where
they describe the same stages they may use diiferent codes. It is not generally possible to map
one scale directly to another even from a simple scale to a more detailed one. Interpolating
growth stages is unwise because the scales are generally ordinal only (stages are ordered but
© 1991 Association of Applied Biologists

562 PETER D. LANCASHIRE ET AL.
plant development between the scale points is undefined and cannot be assumed to be
"linear").
The published scales aim not only to provide a Standard description of growth stages but
also to give a shorthand code which may be used in place of lengthy descriptions. Scales use
different codes to describe similar stages in different crops. The form of codes can also vary:
some use Single letters (Keller & Baggiolini, 1954), some use two digits (Zadoks, Chang &
Konzak, 1974) or three digits (Knott, 1987) and others add various punctuation marks such as
periods (Feekes, 1941; Large, 1954) and commas (Sylvester-Bradley, 1985). This can be
confusing for experimenters working on several crops.
The variety of codes causes problems when storing the Information in present-day Computer
Systems: enough space must be allowed for the widest code and any code validation will
depend on the crop being assessed. For crops without codes a non-standard textual
description must be stored. Retrieving the Information is extremely complicated because of
the difficulty of making comparisons. Some of these problems can be partially overcome with
the latest database Systems.
If descriptions of growth stages were to be standardised they would have the same meaning
in any language. Computer Systems could then use the codes to look up a Standard description
in the Computer user's language. In practice many people remember the meaning of
frequently-used codes and do not need the füll description. A Single set of codes makes this
short-cut easier.
There is a need for a universal scale using a consistent set of numeric codes which can be
readily adapted to all crops. The scale described here was developed jointly by BASF, Bayer,
Ciba-Geigy and Hoechst to meet this need (Bleiholder, Van den Boom, Langelüddeke &
Stauss, 1989). It is to be referred to as the BBCH scale and its associated decimal code as the
BBCH code. A slightly different earlier version of the general scale has already been
published (Bleiholder et al., 1990). The details of the use of the scale for weeds are not covered
here but will be published later.
The general BBCH scale
The BBCH scale is a unified system of many growth stage scales which allows the
description of the growth stages of most crops and weeds. Because of their different
development, the general BBCH scale distinguishes between monocotyledones, dicotyle-
dones, perennial plants, gramineae and vegetatively propagated plants. Within this general
framework more specific scales may be constructed for individual crops and weeds. The
specific scales only add details to the general scale; they do not change it and therefore remain ^
comparable. Where no specific scale yet exists the general scale may be used.
The BBCH scale generally refers to Stands or populations of plants and not individuals. An
average growth stage is recorded at the Start of stages such as flowering where the first
occurrence may be particularly important. This emphasis is to make the scale more useful in
practical agriculture. The scale refers to the main stem of plants, not side shoots, unless stated
otherwise.
The timing of most agricultural operations on crops may be easily expressed in the BBCH
scale but some very precise, crop-specific or usage-dependant timings such as for vegetable
harvesting are not covered. The application of chemicals to seed before sowing is covered but
applications to the soil before the crop is sown or planted are not included because they are
unrelated to the growth of the crop.
Like the cereal scale of Zadoks et al. (1974) and many others published since, the BBCH
scale consists of principal growth stages divided into more specific secondary stages. It is
designed to be sufficiently flexible to describe the development of many important crops and
weeds. The general scale is shown in Table 1.

Uniform decimal growth stage codes 563
Principal growth stages
In order to provide a uniform code applicable to a wide ränge of plant species it is necessary
to use very general development criteria. These criteria have been chosen to make the scale
most convenient for the usual agricultural uses of the crops. Some biological rigour has been
sacrificed in favour of general utility.
For example, germination of plants from true seed, sprouting of vegetative propagules and
bud bursting of perennials are put into one principal growth stage. These are completely
different development stages but are in most cases phenologically analogous. For perennial
plants, the same stage numbers may be used to describe their growth from seed and their
annual regrowth. In such cases, the intended meaning of the scale must be indicated.
The development of harvestable vegetative plant parts and vegetative propagules such as
swollen stems, hypocotyls, roots, tubers, rhizomes, corms and bulbs is covered by growth stage
4, which is also used for booting in cereals. This stage does not cover the development of
leaves, even if they are to be harvested; it is intended for vegetative plant organs not covered
by other parts of the scale. Reproductive organs which develop in parallel with or after the
harvestable vegetative organs (including for seed production) are dealt with by growth stages
beyond 4.
Füll maturity of seeds or fruit has been included in growth stage 8. In this way stage 9 can be
used for senescence.
Secondary growth stages
The secondary growth stages provide the details specific to groups of plants with similar
growth patterns. Species which develop similarly are generally covered by the same scale
using the same dehnitions.
The secondary codes have been chosen so that, where possible, they correspond to ordinal
numbers or percentage values indicating the degree of development within the principal stage.
For example the code "N3" could represent:
• 3rd true leaf, 3rd tiller, 3rd node or
• 30% of the final length or size typical of the species or
• 30% flowers open or 30% plants in flower.
Where the number of items such as leaves or internodes gives an adequate description of the
plant these items are counted. However, counting is not generally useful for processes such as
flowering or the growth in size of fruits and seeds; a measure of the degree of completion of the
process is required. This implies that the final number of flowers or size of fruit be known at
the time of assessment. Clearly it is not possible to predict the future precisely for any
individual plant or even crop but an experienced technician will know the expected (average)
Performance of a species or cultivar under a ränge of growth conditions. The scale has been
designed with this in mind and has a maximum resolution of only ten percent and sometimes
twenty percent for more difficult growth stages.
This criterion is, for many crops, the most reasonable way of assessing development. The
method is already used for oilseed rape (Sylvester-Bradley, 1985) where percentages of
"Potential pods" are estimated. Other scales (Knott, 1987, 1990) concentrate on the first
occurrence of some qualitative measure such as a feature of fruit morphology; this is less
agriculturally useful because it is unrepresentative of the plant or crop as a whole.
Within principal growth stages that are counted or measured secondary code 9 represents
the ninth, 90% etc. or more. The code thus does not distinguish between nine and more than
nine plant parts or between 90% completion and füll completion of a principal stage. This is
unlikely to be a problem as later growth stages generally become more important. The Zadoks
cereal code (Zadoks et al., 1974) makes a similar use of secondary code 9 for leaves and tillers.
Within principal growth stages that are not counted or measured, such as germination.

564 PETER D. LANCASHIRE ET AL.
secondary code 9 represents completion of the stage.
When counting plant parts it is important to have a rule for deciding when to count an item.
This requirement causes most problems with leaves and nodes. The BBCH scale uses the
existing dehnitions of a leaf and node in the temperate cereals (Tottman & Broad, 1987) but
extends them for other crops. The leaf of a dicotyledonous plant should be counted when it
has become visibly separated from the terminal bud. The associated intemode (below)
foUows the same rule. Leaves are counted singly unless they are in pairs or whorls visibly
separated by an internode, when they are counted as pairs or whorls. In any one species leaves
are always counted in the same way.
For crops producing harvestable vegetative plant parts harvest is usually reached at stage
49. Growth stage 89 indicates the end of the reproductive phase of development, when fruit
and seeds are fully mature and are normally harvested. Stage 99 represents the harvested
product and is to be used for post-harvest treatments. Seed-treatment takes place at stage 00.
Some growth stages may overlap or be absent in some species. When two stages overlap,
the Code for the more advanced stage should be used in most cases, where it will describe the
State of the plant adequately. For example, in cereals main shoot elongation occurs before all
the leaves are visible. In some circumstances it may be necessary to record more than one
growth stage of a plant to give an adequate description of its morphology. For example, the
number of tillers produced by graminaceous plants is variable and may be of interest during
and after the later growth stage of stem elongation. Zadoks et al. (1974) also recommended
that tiller numbers be used as supplementary Information. If harvestable vegetative plant
parts are formed during the reproductive growth phase of a plant or if they are the main
subject of interest the vegetative stage is recorded concurrently with the reproductive growth
stage.
The BBCH code
The Code for the BBCH scale uses two decimal digits to represent the principal and
secondary growth stages. Where supplementary Information is not needed a Single two-digit
code may be used. For many crops it can be useful to have additional Information in a
concurrent growth stage. In this case the füll decimal code consists of two groups of two digits.
The more advanced (higher-coded) stage should appear first even if the lower-numbered stage
is of more interest in a particular case. This ensures consistent comparability between codes.
Although the code is represented as a zero-padded cardinal number it should not be inferred
that it has the usual arithmetic properties of cardinal numbers. The scale and its code have
been designed so that the arithmetic value of the code increases as the plant develops. The
arithmetic difference between codes has no meaning. The codes thus define an ordinal
number scale, not an interval scale.
The only useful mathematical Operation that may be performed on the codes is comparison:
an arithmetically greater code indicates a plant at a later growth stage. Sorting codes into
numerical order will thus sort into order of plant development. The zero padding ensures that
character sorting on a Computer (provided its uses the ASCII or EBCDIC infernal codes for
characters) will give the same result. When using supplementary codes, growth stages should
be sorted by the first code (higher-numbered). The supplementary code may optionally be
used as a secondary sorting key.
The BBCH scale in specific crops
The general BBCH scale may be applied as it is but for most crops more specific detail is
required. In particular the BBCH scale must be related to existing scales and to descriptions
of developmental stages peculiar to particular crops. The growth stages of some crop plants