1
Plant nutrient expression
R. D. Voss,
J. J. 1Mortvedt,
ABSTRACT
andJ.
A. Stewart
the situation
where various groups now use either
one or both systems of expression
in publications,
for fertilizer
recommendations,
and for fertilizer
use.
In 1972 the Soil Science
Society
of America
formed the Plant Nutrient
Expression
Committee
to determine current use of elemental and oxide expressions
for P and K. Evaluation
of the current
status was done by a survey of each appropriate
soil
science
or agronomy department
of the land-grant
universities
in the USA, each state’s fertilizer
control official,
representatives
of the fertilizer
industry, and commercial soil testing laboratories.
This
report is a summation of the findings of the Plant
Nutrient
Expression
Committee.
Changingthe expressionof P andK in fertilizers
from the oxide to the elemental basis has long been
considered;all other plant nutrients have beenexpressedon the elementalbasis for manyyears in most
countries. A survey was madeto determinethe current status of the elementalvs. oxide expressionof P
and K in the USA. Results showedthat research information on P and K is nowexpressed on an elementalbasis in mosttechnical journals. Educational
andservice groupstranslate this informationbackto
the oxide expressionfor user groups. Soil test information maybe given on either or both bases, but
fertilizer recommendations
are always given on the
oxide basis. Manufacturersand users are generally
acquainted with only the oxide basis. Advantages
givenfor elementalexpressionwere: simple, less confusion, and moreuniformity. Disadvantageswere:
confusion
resultingfroma change,legal andlegislative
changes
required, increasedcosts, needfor educational programs,andtradition. Alternative coursesof action concerningelemental or oxide expressionof P
and K range from keepingthe present systemto mandatory changeto the elementalexpressionby federal
legislation.
HISTORICAL ASPECTS
It is generally accepted that use of the oxide expression
for reporting the composition of fertilizers
is a carryover
from the chemist’s expression of rock analysis in which
metallic elements were reported as oxides. At one time all
plant nutrients were reported as oxides except for N, which
was reported as NH3. This was changed to the elemental
expression in 1939. Expression of secondary and micronutrients began changing to the elemental basis after this
time and the change was essentially completed during the
past decade. Nowonly three states use the oxide system
for these nutrients. Uniformity, simplicity, and accuracy
are generally given as advantages for changing to the elemental expression. The objections are: required revisions
of fertilizer laws, grades, and formulas; costs involved in a
change; and confusion on the part of the user.
The issue was kept alive in the late 1950’s by the SSSA
Committee on Grades and Ratios. Results of a survey of
SSSA members in 1955 showed that 95% of those responding favored a change to elemental expression (1). In 1957
statement concerning expression of fertilizer
grades on the
elemental basis was prepared by Midwest university agronomists and presented to the Middle West Soil Improvement
Committee. In addition to reviewing the above advantages
and objections to a change to elemental expression, it was
recognized that an intensive educational program was needed
to acquaint users with the resulting changes in fertilizer
recommendations, grades, and ratios.
The Association of American Plant Food Control Officials (AAPFCO), formerly the Association of American
Fertilizer Control Officials (AAFCO),included provisions
for changing from the oxide to elemental basis for P and K
in their model fertilizer
bill at their annual meeting in
1956 (2). Since then, this provision has been retained
each improved version of their suggested uniform fertilizer
bill. Later, several states adopted the newfertilizer bill and
Additional index words: Nutrient expression,
Oxide-elemental
expression,P, K fertilizer labeling.
TuEexpression
of plant nutrients
in some uniform, acceptable
terms has been discussed for
about 50 years
(1).
The major discussion
has
centered
around whether to express
P and K contents of fertilizers
on an elemental or oxide basis.
Expression of all other plant nutrients is on an elemental basis in most countries.
In the USA the P and K contents
of fertilizer
continue to be expressed as oxides by users. / The
desire to express these nutrients
on an elemental
basis has reached various degrees of intensity
in the
last 20 years.
Lack of unanimity has resulted
in
1Professor, Agronomy Dep., Iowa State Univ., Ames,
Iowa; soil chemist, Soils and Fertilizer
Research Branch,
TVA,Muscle Shoals, Ala.; and director of research and development, International
Minerals and Chemical Corp.,
Libertyville, Ill., respectively.
2Chemical symbols are used to conform to journal editorial style, the context will dictate whether these terms
will be phosphate and potash or phosphorus and potassium,
respectively.
35
JOURNAL
36
OF
AGRONOMIC
adopted permissive legislation
for dual labeling (both oxide
and elemental expression of P and K). This made it possible
to change to the elemental basis by administrative
ruling
after
public
hearings
had been held.
The AAPFCO continues to have an active committee on elemental guarantees.
In 1961 a new subcommittee
on elemental
guarantees
was established
by SSSA. The executive board of the SSSA
passed a revision
of a 1960 motion that all references
to
plant nutrients in soil, plant, and fertilizer
analyses in the
Soil Science Society of America Proceedings should be expressed on an elemental basis,
with the option of also including the oxide basis for P and K. The American Society
of Agronomy took similar action for its publications,
effective in January 1963.
During 1961 and 1962 several states
initiated
programs
to make an orderly change from the oxide to the elemental
basis in their extension and experiment station publications.
At the same time, some extension
educational
and service
programs were revised to include both elemental and oxide
expressions
with the ultimate goal of changing completely
to the elemental basis.
The states’
programs appeared to polarize
the positions
of those for and against changing to elemental basis. The
above professional
societies
endorsed the change to the elemental basis,
whereas, in 1963, the Board of Directors
of
the National Plant Food Institute
(NPFI) adopted a resolution supporting the continuation
of the practice
of using
the oxide rather
than elemental
expressions
in stating
guarantees
for "phosphate"
and "potash."
Some states
did
not desire a change to the elemental basis,
but some companies in the fertilizer
industry proceeded to develop programs for adopting elemental expression and to initiate
dual
labeling.
At their annual meeting in 1965, AAFCOpassed a resolution recognizing
that a definite
changeover
period was
necessary for orderly transition
(4). They suggested that
the transition
period extend from 1 July 1966, to 1 July
1976. All fertilizer
labels would list both expressions during
this period.
The oxide basis would be emphasized during
the first 5 years and the elemental basis emphasized during
the second 5-year period. The elemental basis only would
be used after 1 July 1976.
The decade from 1965-75 was one of reaffirmation
by
various groups but essentially
a cooling-off period. In 1971,
the Executive
Committee of the SSSA reaffirmed
their
previous position favoring change to elemental expressions
of P and K, but in the same year, The Fertilizer
Institute
(TFI), successor
to NPFI, recommended continuation
the use of the P2Os and K20 expressions.
The AAPFCO
reaffirmed
their 1965 resolution
in 1972 (3). Educational
programs were initiated
by institutions
in several states but
eventually faded as other needed changes failed to materialize. Use of elemental expressions,
along with metric terms,
became firmly established
in research and technical publications. However, the manufacturers,
marketers,
and users of
fertilizers
continued to use the oxide form of P and K, along
with English measurements.
Those who performed educational and service functions for the marketers and users of
fertilizer
translated
research information from the elemental and metric expressions to the equivalent
information
in
oxide and English expressions, respectively.
SURVEY
METHODS
Questionnaires
were prepared b~ the Plant Nutrient Expression
Committee to determine
the present use of elemental and oxide expressions
in fertilizer
guarantees and
EDUCATION
Table 1-Response of agronomy or soil science departments
to plant nutrient expression questionnaire
No.of states
Elemental Oxide Both Either
Question
1. Yourdepartmentalpolicyspecifies the use
of whichexpression
in state publications
and reports?(15 had no policy}
1
2. In classroom
teachingwhichexpression
is used?
1
3. Forthosehavingsoil textinglaboratories:
a. Soil test resultsare expressed
in which
form?
27
b. Fertilizerrecommendations
areexpressedin whichform?
0
4. In extensionpublicationswhichhavegeneral
distributionin yourstate, whichexpression
is used?
0
5. In newsreleases initiated by yourextension
specialists, whichexpression
is commonly
used?
0
6. Hasyourstatehadanextension
publication
discussing
the conversion
fromthe oxideto
the elementalexpression?
7. Doesyourstate nowhavesuch a publication?
8. Hasyour state had an extensioneducational
program
on the conversionfromthe oxide to
the elementalexpression?
9. Doyounowhavethis as an ongoing
extensioneducationalprogram?
5
11
6
1
37
0
10
3
0
31
9
0
24
13
3
30
10
0
Not
applicable
Yes
No
14
7
26
32
1
1
18
22
1
8
32
1
recommendations,
soil test reports,
and educational
programs on fertilizer
use. Appropriate
questionnaires
were
sent to each soil science or agronomy department in the 50
states and Puerto Rico, each state’s fertilizer
control official,
commercial soil testing laboratories
which were identified
by
the federal extension service, and selected companies within
the fertilizer
industry.
The survey was completed in 1974.
In addition to requests for answers to specific questions,
the questionnaires
also asked the respondent to record his
opinion of advantages and/or disadvantages
of the elemental
expression.
Completed questionnaires
were returned
from
41 of the 51 agronomy or soil science departments,
43 of
the 51 state fertilizer
control officials, all of the 15 fertilizer
companies, and 82 of 203 commercial soil testing
laboratories.
RESULTS
OF SURVEY
Agronomy or Soil Science Departments
The survey form asked for information on the
use of the elemental expression of P and K in the
research, teaching, service, and extension functions
of the department; questions
and responses are
given in Table 1.
There is no consistent
policy among agronomy
or soil science departments concerning elemental
or oxide expressions except, of course, regarding
publication
requirements for technical
journals
(Question 1). Graduates should be knowledgeable
about both elemental and oxide expressions
because all but two departments use both expressions
in the classroom (Question 2).
Two-thirds of the soil testing laboratories operated by institutions or agencies report soil test resuits in the elemental form, but all of these labora-
PLANT
VOSS ET AL.:
NUTRIENT
Table2-Advantages
anddisadvantages
of elementalexpressionas givenby the agronomy
or soil sciencedepartments
Advantages
Simpler
Moreaccurate
Moreuniform,less confusion
None
Other
No.of
states
14
3
19
3
3
No. of
states
Disadvantages
Educational
needs
Traditionto overcome
Confusionin changing
None
Other
18
5
11
3
3
EXPRESSION
37
On the basis of this survey it appears that the
change to the elemental expression is being assimilated by the academic community, but the oxide
expression still predominates by the fertilizer
user.
Impetus for changing to the elemental expression
at the user level appears to have declined in recent
years.
Fertilizer
Control Officials
Table3--Response
of fertilizer controlofficials
Question
1. Would
a changein expression
of plantnutrientsrequirea
change
in state laws?
2. Coulda changein expressionof plant nutrients bemadeby
changingexistingregulations?
3. Woulda changein plantnutrientexpression
affect
licensingor registration
of fertilizergrades?
4. Areduallabels (bothoxideandelementalbasis) for
analysisof P and Kpermittedin yourstate?
5. Howdothe fertilizer lawsor regulationsin your state
requirethat fertilizer guarantees
be expressed?
Oxide
Plant Nutrient
Elemental
N
42
0
P
39
2
K
2
39
Secondarynutrients
39
3
Micronutrients
40
2
No.of states
Yes
No
20
19
16
16
9
32
30
11
Either
0
1
1
1
1
tories give fertilizer
recommendations in the oxide
or both forms (Question 3). Thus, users of this information continue to receive the information as
pounds/acre of P205 and K20.
Most extension educational
programs use the
oxide expression. If the elemental expression is
used, it is used in conjunction with the oxide expression (Question 4). Educational programs on
the conversion from oxide to elemental expressions
were initiated by 14 states (Question 5) but current
programs including publications
have declined to
7 states (Question 6). The number of extension
educational programs on conversion from oxide to
elemental expressions has similarly decreased (Questions 7 and 8).
Primary advantages given for the change were
that elemental expression
of P and K would be
simpler (Table 2). One problem with the present
system is that more than one term for each plant
nutrient is now used, i.e., phosphate, phosphorus,
phosphoric acid, and phosphorus pentoxide,
and
potash, potassium, and potassium oxide, respectively.
The change also would result in all plant nutrients being expressed on an elemental basis so there
should be less confusion than with P and K being
expressed as P2Os and K20, respectively.
The main
disadvantages listed were the need for educational
programs if the change were made and also confusion due to resulting changes in fertilizer
recommendations and fertilizer
grades. The need to overcome certain traditions was also expressed.
Results of the survey of fertilizer
control officials
are summarized in Table 3. One reporting
state (Alaska) does not have a fertilizer
law at this
time.
Changing
plant nutrient expressions from P20
s
and K20 to P and K would require
legislative
changes in 20 states (Question 1). Such changes in
plant nutrient expression could be made by revising
existing regulations in 16 states (Question 3); this
could be accomplished easier than changes in state
laws. In either instance the effective date of change
could be publicized well ahead of time. It is not
clear how the remainder of the reporting states
would effect a change; this may have been due to
the ambiguity in Questions 1 and 2.
Somestates require licensing or registration of all
fertilizer
grades sold in the state, while others do
not. Changing to elemental expressions would require changes in listing of fertilizer
grades in 9
states (Question 2). Allowable tolerances in fertilizer guarantees also would be affected.
Dual labels (guarantees of P and K on both oxide
and elemental basis) are permitted in 30 states
(Question 4). Dual labels have usually stressed the
fertilizer
grade on the N-P2Os-KzObasis with the
elemental basis usually printed in smaller letters.
The purpose of dual labels was to educate users on
the new grades which would result from a change
to elemental guarantees.
Most states require that N, secondary, and micronutrients be expressed on the elemental basis, while
P and K are expressed as P~Os and K~O, respectively (Question 5). Both nutrients
may be expressed
on either basis in Idaho, while the secondary nutrients may be expressed either way in North Carolina.
Fertilizer laws in Illinois and Wyomingrequire elemental expression for all plato nutrients,
while
Florida and Texas require oxide expressions for all
plant nutrients except N.
Provision for comments both for and against a
change to elemental expression was included on the
survey forms. Several are discussed here because
they point up important aspects, both pro and con,
of the proposed change to the elemental expression.
Each main topic is begun by a quotation
which
points to a problem or potential problem.
38
JOURNAL
Table 4--Response
of fertilizer
OF AGRONOMIC EDUCATION
companies
Table 5--Response
of commercial
soil testing laboratories
No. of laboratories
No. of companies
Question
1. Mycompany’s position--to change
fromthe traditional oxide to the
elemental expression of P and K is?
2. The companyposition relative to
"metrication" is:
3. As a company,we maintainsoil and/or
planttesting facilities:
4. Mycompany
engages in the fertilizer business
in countries other than the USAand Canada:
5. If a changeto the elemental basis were
contemplatedwe would prefer a lengthy
period (5 to 10 years) was opposed to
short conversionperiod.
In favor Indifferent
Opposed
6
3
5
Elemental
1. Soil test results are expressed in whichform?
2. Fertilizer recommendationsfor phosphorus and
¯ potassium are expressed in which form?
2
Yes
No
4
11
7
8
3
Question
3. Are factors for convertingthe oxide to the e]emental
expression, or vice versa, given on the reports?
4. Do you use the oxide expression for any other
elements?
5. Has your laboratory ever provided educational
materials discussing the conversion from the
oxide to the elemental expression?
6. Does your laboratory nowhave such a publication?
43
12
Oxide Both
30
9
58
10
Yes
No
13
69
8
72
18
9
62
69
12
1. "Both industry and growers are comfortable with the
existing method of expression, and until there is an
indication
that the grower-consumer wishes the
change, I see no real impetus to press for a change
just for the sake of simplification of chemical identification and conversion."--This
summarized the attitudes of many people, including some fertilizer
control officials, and others associated with fertilizer production, sales, and use. Few see any real need to
make the proposed change, since the present system
is now understood and fertilizer
recommendations
are made on the basis of N-P2Os-K20.
2. "If a change to elemental guarantees of P and K were
made, the minimumplant nutrients, grades, and ratios
which were written into the law would be affected."-Concern was expressed over changes required in many
fertilizer laws if a change to elemental were made. If
the whole number concept of fertilizer
grades were to
be continued with the elemental expression of P and
K, guaranteed nutrient content would decrease. For
example, ordinary superphosphate, 0-20-0, would become 0-8.7-0 which would be called 0-8-0, unless
fortified
to become 0-9-0. Allowable tolerances in
fertilizer grades also would have to be altered with a
change to the elemental basis.
3. "A change would bring confusion to the consuming
public. There is need for education and conditioning
first."--Many
who do not understand the change to
elemental basis will have the impression that the plant
nutrient content of fertilizer has been decreased. This
will also require educational programs.
4. "A change to elemental guarantees would result in
fertilizer
being expressed on the same basis as plant
and soil analysis, thus reducing confusion which currently exists."--Results of plant analyses have been expressed on an elemental basis for manyyears. Several
soil testing laboratories have changed their method of
reporting results and fertilizer
recommendations to
both oxide and elemental bases of P and K in recent
years. This has resulted in confusion to the grower.
It is argued that it would be easier to change P and K
to the elemental basis than to change all of the others
to the oxide basis to reduce the confusion.
5. "Simply make a change to elemental guarantees mandatory, give everyone sufficient time to comply and
the change will be made."--This opinion was expressed
by several respondents who think that the change to
the elemental basis could be accomplished if (a)
nationwide change would be mandatory at a given
date and (b) if sufficient time were allowed to make
the required changes in fertilizer
laws, regulations,
and labels, as well as to conduct the necessary educational programs.
Fertilizer
Industry
Six of the respondents
stated that their company
favored
change to the elemental
expression
of P
and K while three were opposed and six were indifferent
to a change (Table 4). The interpretation
here is that 60% of the companies surveyed could
be classified
as "not in favor" of a change. Those
companies surveyed were primarily
basic producers,
most of whom also conduct a retail
fertilizer
business through a network of retail
outlets.
No attempt was made to seek the views of the thousands
of independent retail
fertilizer
outlets
throughout
the country.
It might be assumed that these companies,
dealing as they do with farmers,
would be
even less enthusiastic
about changing the mode of
expression
for fertilizer
goods. The companies
which were selected,
however, account for the bulk
of the fertilizer
materials
business.
As previously
mentioned, TFI, representing
the fertilizer
business
at all its levels, reaffirmed its opposition to a change
to elemental expression
of P and K in 1972.
It is of note that the respondents opted strongly
for a short rather than a long conversion period, if
a change were to be made. Many felt
that
the
change in expression
might best be made to coincide with conversion
to the metric system, if and
when that occurs.
Attitudes
concerning
metrication
were mixed
(Question
2). Five companies were in favor and an
equal number indifferent
to the change to the
metric
system,
with three
companies
being opposed. Significantly,
only three of seven companies
engaged in international
fertilizer
activities
or operations were in favor of conversion
to the metric
system.
Comments on the proposed
change to the elemental expression
were numerous;
the following
are given to bring out the diversity
of opinion.
VOSS ET AL.: PLANT NUTRIENT EXPRESSION
Table6--Advantages
anddisadvantages
for changing
from
the oxideto the elemental
expression
as enumerated
by
82 commercial
soil testinglaboratories
39
cline in the educational materials now being made
available by the commercial soil testing laboratories
(Questions 5 and 6).
No.of
No.of
The survey further indicated that past and presAdvantages
laboratories Disadvantages laboratories
ent
use or lack of use of the elemental expression
Simpler
17
Educational
needs
15
by commercial soil testing laboratories
reflects
More
uniform,
lessconfusion20
Tradition
to overcome 5
Confusion
in changing 12
None
3
mainly
the
working
relationship
which
the
laboraOther
28
Cost
2
None
5
tory
has
with
industry
and]or
user
groups.
This
Other
7
group reflects similar reasons for advantages and
disadvantages for the elemental expression as those
given
by educational institutions
(Table 6). The
1. "It makesno difference to the growingcrop."
2. "Neither the farmer nor our industry has any benefit
predominant advantages were simpler, more unito be gained."
form reports, and less confusion in recommenda3. "Commonsense--the problems are nil and just
tions. The main disadvantages
were educational
dreamed up."
needs,
confusion
in
changing
to
the elemental ex4, "Can’t see howlabel will affect quantity, quality, or
pression,
and
need
to
overcome
tradition.
value of fertilizer."
5. "The required state law changesopen the door for inadvisable proposals. The benefit from elemental expression is not worth the confusion and the legal
International Elemental Expression of P and K
fuss."
6. "It will come with the metric system--we might as
Several countries have recently changed from the
well get on with it."
oxide to the elemental system of labeling P and K
7. "Howmanyfarmers will be able to understand and
use 7-13-12 fertilizer at 600 kg/ha within the next 10
in fertilizer
grades. Denmark, Ireland, New Zeato 20 years?"
land, and Norway changed to the elemental system
8. "Personally I started off favoring it but found myself
about 1960. Sweden changed to the elemental syshard-pressed to explain its worth."
tem in 1970, the Republic of South Africa in 1972,
The general consensus from the diverse answers
and Australia
in 1973. Botswana, Lesotho, and
and comments is summed up in the following comSwaziland in Africa also have made the change and
ment, "We’d rather not, but any change should be
Finland is now in the transition stage, using a dual
made at the time of metric conversion and over a
labeling system. Japan is using both oxide and elerelatively short conversion period."
mental expression in their scientific
and technical
terminology.
Soil Testing Laboratories
The conversion process in Sweden was typical.
The change was favored by the extension service
Results of the survey of 82 commercial soil testand university system, but there was some opposiing laboratories
on use of oxide or elemental extion by the fertilizer
industry. Most young farmers
pressions in reporting soil test results and fertilizer
attend agricultural schools, so the required educarecommendations and on educational
information
tional program was relatively
easy. Dual labeling
are given in Table 5. Commercial soil testing laboraof fertilizer
bags began in 1970 for a 2-year period,
tories report soil test results about equally in eleand there were no real problems in implementation.
mental or oxide expressions
(Question 1). Some
Fertilizer sales were not affected by the change to
laboratories do not give actual values of available P
elemental expression, and educational programs are
and K but rather report their results as low, me,dicontinuing.
um, or high. Most laboratories
responding in this
In Australia, the decision was made to convert to
survey (83%) give fertilizer
recommendations in the
elemental expression at the same time that the
oxide form (Question 2), however, Thirteen laboracountry converted to the metric system. A dualtories, including those which report soil test results
label system began in January 1973, but was dison the elemental basis, also give conversion factors
continued 2 months later in favor of the elemental
in their reports. Also, eight of the reporting laborasystem only. Conversion to the elemental exprestories use the oxide expression for available nutrision probably was easier in Australia because both
ents other than P and K. Thus, there is a great dithe fertilizer
industry and growers tend to discuss
versity in soil test reporting procedures.
fertilizers
by name rather than grade. A massive
Some educational endeavors have been made, but
educational program was also undertaken to give
certainly by a minority of these laboratories. As inconversion tables which included the change to the
dicated by the survey of the agronomy and soil scimetric system as well as to elemental expression for
ence departments (Table 1), there is a similar deP and K.
4O
JOURNAL OF AGRONOMICEDUCATION
The Central
Treaty Organization
(CENTO)
seminar on fertilizer
analytical methods, sampling,
and quality control, held in Lahore, Pakistan, in
March 1974 also favored the adoption of expressing
guaranteed analyses for all nutrients on the elemental basis as soon as possible.
The Council for Mutual Assistance (CMEA)at its
March 1976 session in Moscow, has recommended a
gradual change of oxide to elemental expression for
all nutrients in plant tissue, soil, and fertilizer materials to its member countries (Bulgaria, Czechoslovakia,
German Democratic Republic, Hungary,
Mongolia, Poland, Romania, and USSR).
Many developing countries are now considering
the adoption of fertilizer
legislation.
Use of elemental or oxide expression of P and K in their fertilizer guarantees will probably depend on the system
used in the countries from which they import fertilizers. If the fertilizer
exporting countries later
change their method of plant nutrient expression,
corresponding changes in fertilizer
legislation would
be required in all affected countries.
Many countries,
including Australia,
Canada,
India, Japan, New Zealand, the Republic of South
Africa, and the United Kingdom, are now in the
process of converting to the metric system. By
1976 all countries in the European Econ,mic Community will have converted entirely to this system
of measurements. Several bills concerning conversion to the metric system have been introduced
in the U. S. Congress during the past decade. The
Metric Conversion Act was signed into law (PL 94168) inDecember 1975. This act calls the establishment of a U. S. metric board to coordinate a voluntary conversion to the metric system as the predominant but not exclusive
system of measurement. No timetable for mandatory conversion was
included in this law.
CONCLUSIONS
A change to elemental expression of all plant nutrients in all phases of the agricultural industry has
met with resistance in some quarters.
Agriculture in the USAcan be divided into research, education, service, regulatory, mining, manufacturing,
marketing, and user groups regarding
plant nutrient expressions. Research now uses the
elemental expression, resident education, extension
and regulatory
services
use both elemental and
oxide expressions and mining, manufacturing, marketing, and user groups use the oxide expression
for P and K contents of fertilizers.
Educational
and service groups are the translators
of research
information in the elemental to the oxide expression.
Those who favor change to elemental expression
give as primary reasons: simpler, less confusion,
and more uniformity for quantitative expressions of
plant nutrients in plant analyses, soil test measurements, and nutrient content of fertilizers.
Those
who oppose the change give as primary reasons:
confusion in changing, legal and legislative requirements, educational needs, cost, and tradition.
There are several alternative
courses of action
and possible consequences of each:
1. Let the current system continue.--Research information wouldthus continue to be published on the elemental basis and fertilizer manufacturers and users
wouldcontinue with the oxide basis for P and K-only.
Research, extension, and industry agronomists would
continue as the translators of research informationregardingfertilizer use.
2. Encouragethe complete use of the elemental expression for plant and soil analyses through all organizations and institutions but continue the oxide expression at the use level for P and K contents of fertilizer.
--Manysoil testing laboratories wouldhave to change
their methodof reporting soil test results. Fertilizer
recommendationswould continue on the oxide basis
for P and K so the user wouldnot be affected.
3. Encouragethe few remaining states to pass permissive
legislation for elementalexpressionof all plant nutrients in fertilizer guarantees.--Suchlegislation would
result in a moreuniformtransition scheduleif the decision were madeto change to elemental expression
on a nationwidebasis.
4. Change.to elemental expression all plmat nutrients on
a nationwide basis on a specified date.--An extensive
educational program may be required to acquaint
users with changes in fertilizer recommendations,
grades, and ratios. Educational materials regarding
conversion should be prepared and distributed jointly
by ASA,SSSA,the fertilizer industry, and both state
and federal extension services. Duallabeling of fertilizers for a short period maybe necessary. Changesin
state fertilizer laws maybe required tmless permissive
legislation is already allowed.
5. Pass federal legislation to mandatethe changeto elemental expression of all plant nutrients if and whena
change to the metric system is madein the U. S.-Changeto the metric system of measurementswill require changesin state fertilizer laws as well as extra
educational programs. Therefore, it wouldbe preferable to change to elemental expression at the same
time if the changeis to be made. Educational materials should be prepared and distributed jointly as discussed in Alternative 4.
6. Return to the earlier position where the expression
P2Os and K20 were universally recognized and used
at all levels.--It should be acknowledgedthat the expression of fertilizer P and K on the elemental basis
and in metric units is a foreign languageexcept in the
academic community.A commonbasis of expression,
no matter what its imperfections, maybe preferable
over the current use of oxide and elemental expressions.
ETUK & COLLINS:
FARMLANDS IN NIGERIA
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