PUBLIC REVIEW DRAFT DRAFT UGANDA STANDARD  
  DUS ARS 1482  
First  Edition  
2021-mm-dd 
 
 Reference number  
DUS ARS 1482 : 2020 
© UNBS 2021  
   
Granula ted superphosphate fertilizers — Specification  
 PUBLIC REVIEW DRAFTDUS ARS 1482: 2020  
ii                © UNBS  2021  - All rights reserved  
 Compliance with this standard does not, of itself confer immunity from legal obligations  
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responsible for its correct application  
© UNBS 20 21 
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Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry of Trade, Industry and 
Cooperatives established under Cap 327, of the Laws of U ganda, as amended. UNBS is mandated to co -
ordinate the elaboration of standards and is  
(a) a member of International Organisatio n for Standardisation (ISO);  
(b) a contact point for the WHO/FAO Codex Alimentari us Commission on Food Standards;  and  
(c) the Nationa l Enquiry Point on TBT Agreement of the World Trade Organisation (WTO).  
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a given field or area and consist s of representatives of 
consumers, traders, academicians, manufacturers, government and other stakeholders.  
Draft Uganda Standards adopted by the Technical Committee are widely circulated to stakeholders and the 
general public for comments. The committee r eviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
This Draft Uganda Standard, DUS ARS 1482: 2020 , Granulated superphosphate fertilizers — Specification , is 
identical with  and is being  reproduced from an African  Standard , ARS 1482: 2020 , Granulated superphosphate 
fertilizers — Specification , and is proposed fo r adoption as a Uganda Standard . 
The committee responsible for this document  is Technical Committee UNBS/TC 2, Food and a griculture , 
Subcommittee SC 2 0, Agrochemicals and veterinary drugs . 
Wherever the words, “ African  Standard" appear, they should be replaced by "Uganda Standard."  
 
  PUBLIC REVIEW DRAFTAFRICAN 
STANDARD ARS  
1482 
First Edition 2020 
 
 Referen ce No. ARS 1482:2020(E) 
ICS 65.080  
 
 
© ARSO  2020 
  
 
  
 
  
 
 
 
Granulated superphosphate fertilizers — Specification  
 
 
 
  
 
  
 
  
 
  
 
  
 
 
 
 PUBLIC REVIEW DRAFTARS  1482:2020  
ii © ARSO 20 20 — All rights reserved  
Table of contents  
 
1 Scope  ............................................................................................................................................. 1  
2 Normativ e references  ..................................................................................................................... 1  
3 Terms and definitions  ..................................................................................................................... 1  
4 Requirements  ................................................................................................................................. 2  
4.1 Description  ............................................................................................................................. 2  
4.2 General requirements  ............................................................................................................ 2  
4.3 Physical  .................................................................................................................................. 2  
4.4 Heavy metal contaminants  .................................................................................................... 2  
5 Sampling  ......................................................................................................................................... 3  
6 Tests  ............................................................................................... Error! Bookmark not defined.  
6.1 Methods of test  ...................................................................... Error! Bookmark not defined.  
6.2 Inspection ............................................................................... Error! Bookmark not defined.  
7 Compliance  ..................................................................................................................................... 3  
8 Packaging and labelling  ................................................................................................................. 3  
8.1 Packaging  .............................................................................................................................. 3  
8.2 Labelling ................................................................................................................................. 3  
9 Certificate of analysis  ..................................................................................................................... 4  
10 Material safety  ................................................................................................................................ 4  
Annex A (normative)  Determination of free phosphoric acid  ................................................................. 5  
Bibliography  ............................................................................................................................................ 7  
 PUBLIC REVIEW DRAFTARS 14 82:2020  
© ARSO 20 20 — All rights reserved iii  
Foreword 
 
The African Organization for Standardization (ARSO ) is an African intergovernmental organization 
established by the United Nations Economic Commission for Africa (UNECA) and the Organization of 
African Unity (AU)  in 1977. One of the fundamental mandates of ARSO is to develop and harmoniz e 
African Standards (ARS) for the purpose of enhancing Africa’s internal trading capacity, increase 
Africa’s product and service competitiveness globally and uplift the welfare of African communities.  
The work of preparing African  Standards is normally carried out through ARSO  technical committees. 
Each Member State  interested in a subject for which a technical committee has been established has 
the right  to be represented on that committee. International organizations, Regional Economic 
Communities (RECs), governmental and non- governmental  organizations , in liaison with ARSO , also 
take part in the work.   
ARSO  Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.  
 The main task of technical committees is to prepare ARSO  Standards. Draft ARSO  Standards 
adopted by the technical committees are circulated to the member bodies for voting. Publication as an ARSO  Standard requires approval by at least 75 % of the member bodies casting a vote.  
 Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ARSO  shall not be held responsible for identifying any or all such patent rights.  
 This African Standard was prepared by the ARSO Technical Harmonization Committee Number 5 on 
Chemistry and Chemical Engineering (ARSO/THC 05) . 
 
    
© African Organisation for Standardisation 2020  — All rights reserved
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Introduction 
 
Mineral fertilizers are materials, either natural or manufactured,  containing nutrients essential to 
normal growth and development of plants.  Various studies, including those conducted by FAO, have 
established beyond doubt the existence of a close relationship between fertilizer  consumption level 
and agricultural productivity . Crop yield levels are generally higher in those countries where fertilizer 
consumption levels are  also high. Amongst the various agricultural inputs , fertilizers, perhaps next 
only to water, contribute the maximum to increasing agricultural  production. It has been estimated that 
about 50 percent of the increase in agricultural production witnessed dur ing the last decad e in 
developing countries is attributable to fertilizer use . 
 
Most developing countries have assigned special priority to  fertilizers in their efforts to modernize their 
agricu lture. It has also  been increasingly realized that it is relatively cheaper and more in a country's 
long-term interest t o import fertilizer  than food -grains . Many  developing countries, within the 
limitations imposed by availability of raw  materials, financial resources, techni cal manpower, etc , are 
also making serious efforts to set up fertiliz er plants so as to meet part or all of  their fertilizer 
requirements . This phenomenon has resulted in substantia l growth in fertilizer consumption. 
 Phosphorus is an important consti tuent of the ea rth's crust, but has  been concentrated over 
geological time in deposits of phosphate rock  (formed mainly from the r emains of aquatic organ isms), 
and is present in most natural and cultivated soils in insufficient quantity for full c rop growth. The 
sources from wh ich phosphorus is ob tained for use in fertilizer s are:  (i) phosphate roc k deposits, by 
far the most important s ource, and ( ii) basic slag, a by -product of ·the steel industry . 
 Plants take phosphorus  from the soil solution in the form of phosphate ions (HP O
4-- and H 2PO 4), so 
that for fertilizer phosphorus to be available it must be released in ionic form to the soil solution. The 
phosphorus in fertilizers occurs in various chemical and physical forms  whose availability varies very 
much.  
   PUBLIC REVIEW DRAFTPUBLIC REVIEW DRAFTARS 14 82:2020  
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Granulated superphosphate fertilizers — Specif ication  
  
1 Scope  
 
This African  Standard specifies requirements, sampling method and test methods for granulated 
superphosphate fertilizers.   
 
2 Normative references  
 The following referenced documents are in dispensable for the application of this document. For dated 
references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.  
 AOAC 969.02, Phosphorus ( total) in fertiliz ers — Alkalimetric q uinolinium m olybdophosphate method 
 
AOAC 993.31, Phosphorus ( available) in fertilizers — Direct extraction method  
 
AOAC 2006.03, Arsenic, cadmium, cobalt, chromium, lead, molybdenum, nickel, and selenium in 
fertilizers  — Microwave diges tion and inductively coupled plasma- optical emissi on spectrometry  
 
EN 12048, Solid fertilizers and liming materials — Determination of moisture content — Gravimetric 
method by drying at 105 ±2 °C 
 
ISO 5316, Fertilizers — Extraction of water- soluble phosphat es 
 
ISO 7409, Fertilizers — Marking — Presentation and declarations  
 
ISO 8157, Fertilizers and soil conditioners — Vocabulary  
 
ISO 8189, Solid fertilizers — Determination of moisture content — Gravimetric method by drying 
under reduced pr essure  
 
ISO 8397, Solid fertilizers and soil conditioners — Test sie ving 
 
ISO 14820- 1, Fertilizers and liming materials — Sampling and sample preparation — Part 1: 
Sampling  
 
ISO 14820- 2, Fertilizers and liming materials — Sampling and sample preparation — Part 2: Sample 
preparation  
 
ISO 17318, Fertilizers and soil conditioners — Determination of arsenic, cadmium, chromium, lead 
and mercury contents  
 
3 Terms and definitions  
 For the purpose of this standard the terms and definitions in ISO 8157 and the follo wing apply . 
 3.1 
superphosphate  
The product  obtained by treating phosphate rock with sulphuric acid. It is also known as single 
superphosphate.  
 
3.2 
concentrated superphosphate  
The product obtained by treating phosphate rock with phosphoric acid or phosphoric acid and sulphur ic 
acid mixture . It is also called ‘enriched superphosphate’ or ‘triple superphosphate’.  
 
3.3 
available phosphorus  
the fraction of phosphorus available to plants. This is the sum of the water -soluble and citrate- soluble 
phosphorus.  
 AFRICAN  STANDARD  PUBLIC REVIEW DRAFTARS 14 82:2020  
2 © ARSO 20 20 — All rights reserved 3.4 
total phosphorus  
the sum of available and citrate -insoluble phosphorus  
 
4 R equirements  
 
4.1 General requirements  
 
The fertilizer shall be homogenous, free- flowing  in the form of granules, pellets, or crystals  and free 
from foreign matter  and hard lumps  
 
4.2 Physical  requirem ents 
 
When test sieved in accordance with ISO 83 97, the particle size for granular fertilizer shall be such 
that not less than 90 %, by mass of the fertilizer shall be of particles in the size range of 1 mm to 4 
mm. Not more than 5% shall be below 1 mm.  
 
4.3 Chemical  requirements  
 
Superphosphate fertilizer shall comply with the following compositional limits  in Table 1 
 
Table 1 —C hemical requirements for superphosphates  
 
Sl. 
No.  
Characteristic  Requir ement, %, by mass Method of test  
Grade 1 Single 
Supe rphosphate  Grade 2 Single 
Superphosphate  Triple/ 
Concentrated 
Superphosphate  
(i) Water- soluble 
phosphate (as P 2O5), 
min  
18.0  
14.0  
40  
ISO 5316 
(ii) Available phosphate  
(as P 2O5), min 21.5 16.5.  46.0 AOAC  969.02 / AOAC 
993.31  
(iii) Free phosphoric ac id 
(as P 2O5), Max  4.0 4.0 4.0 Annex A  
(iv) Moisture, max  5.0 5.0. 4.0 EN 12048/ ISO 8189  
(v) Sulfur ( as S), min 11 11 11 ISO 15178/ EN 16032  
 
4.4 Heavy metal contaminants  
 
The heavy metal contaminants, if present, shall not exceed the limits stipulated in Table 2.  
 
Table 2 — Heavy metal contaminants limits  
 
Sl. 
No. Parameter  Limits, mg/kg  Test method  
i) Arsenic, As, max.  40 AOAC 2006.03 / ISO 17318  
ii) Cadmium, Cd, max.  45 AOAC 2006.03/ ISO 17318  
iii) Mercury, Hg, max.  0.1 AOAC 2006.03 / ISO 17318  
iv) Selenium, Se, max.  1.0 AOAC 2006.03  
v) Lead, Pb, max.  30.0 AOAC 2006.03 / ISO 17318  
vi) Nickel  120 AOAC 2006.03 / ISO 17318  
vii) Chromium, Cr  Max.  500 AOAC 2006.03 / ISO 17318  
 PUBLIC REVIEW DRAFTARS 14 82:2020  
© ARSO 20 20 — All rights reserved  3 5 Sampling  
 
Sampling and sample preparation for inspection and testing shall be carried out in accordance with 
ISO 14820 p arts 1 and 2. 
 
6 Com pliance  
 The lot shall be deemed to comply with the standard if after  inspection and testing it complies with the 
require ments of this standard.  
 
7 Packaging and labelling 
 
7.1 Packaging 
 
The fertiliser shall be packed in clean, non- defecti ve and strong packages . The material of which the  
package is made shall be such as to protect the contents from moisture and also not lead to easy 
rupture during handling, transportation and storage.  
 
7.2 L abelling  
 
7.2.1 Each  package of the fertiliser  shall be legibly and indelibly marked in accordance with ISO 
7409, and with the following particulars:  
 
a) Name of the product  as superphosphate fertilizer ; 
 
b) type;  
 c) g rade  
 
d) n ame and physical address of the manufacturer/packer ; 
 
e) minimum  water -solub le phosphates stated as P
2O5 content of the material ; 
 f) net weight of the material in the package; 
 
g) content  of fluorine and s ulfur; 
 
h) manufacture and expiry  or best before date; 
 i) l ot or batch number ; 
 
j) h andling,use  and storage instructions ; and 
 
k) warning statement similar or closely similar in meaning to the statements in 1,  2 and 3 
preceded by the words: “WARNING”:  
 1) do not swallow. The dust from this product may act as an irritant, avoid inha lation or 
contact with eyes and skin;  
 2) this product may contain fluorine as an impurity; do not feed this product to livestock or 
use in feedstock mixtures. If top dressing pastures do not graze for 3 weeks or until rain or irrigation is received; and 
 
3) this product may contain heavy metal as impurities; its repeated use may therefore lead 
to accumulation of the same in the soil. Depending  on soil characteristics, irrigation 
water quality, plant species and variety, crop uptake of heavy metals may exceed the  
maximum limits allowed in local food standards; in pasture, the offal from grazing animal 
may also exceed these limits; therefore its application in accordance to local regulation 
is advised.  PUBLIC REVIEW DRAFTARS 14 82:2020  
4 © ARSO 20 20 — All rights reserved  
7.2.2 Bulk containers  
 Where the product is distributed in bulk,  the marking  information shall accompany the del ivery note to 
the purchaser.  
 
8 Certificate of analysis 
 A certificate of analysis stating the mini mum percentage levels of plant nutrient elements shall 
accompany every lot or consignm ent of  the fertilizer . 
 
9 Material safety  
 
Each consignment must be accompanied by a Material Safety Data Sheet (MSDS) and a c ertificate of 
analysis (COA).  
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© ARSO 20 20 — All rights reserved  5  
Annex A  
(normative)  
 
Determination of free phosphoric acid  
 
 
 A.1 Purpose  
 This method determines the percent of phosp horic acid (P
2O5) in commercial fertilizers by col orimetry.  
 A.2 Reagents and apparatus  
 1) An Atomic Absorption Spectrophotometer or a suitable colorimeter.  
 2) Nitric Acid (HNO
3), 1.42 specific gravity.  
 3) Hydrochloric Acid (HCl), 1.19 specific gravit y.  
 4) Potassium Phosphate, Monobasic (KH
2PO 4), Primary Standard Grade, dried at 105- 110 °C 
for several hours prior to use.  
 
5) Ammonium Molybdate ((NH 4)6MO 7O24•4H 2O), Reagent Grade.  
 
6) p- Methylaminophenol Sulfate, Reagent Grade.  
 7) Sodium Acid Sulfi te (NaHSO
3), Reagent Grade.  
 
8) Cuvets, optical g lass, matched, 10mm path length.  
 
NOTE  If available, an optical glass, automatic flow -through cuvet may be used.  
 A.3 Preparation of s tandard solutions  
 
Phosphate Stock Solution: Weigh 0.4394 g of dried, pri mary standard KH
2PO 4 into a 500- mL 
volumetric fl ask. Add 30 ml of HNO 3 and 5 ml of HCl and boil until brown fumes have been expelled. 
Dilute to volume with distilled water.  
 
5 ppm Working Standard: Pipette a 5- ml aliquot of the phosphate stock solution in to a 200- ml 
volumetric flask and dilute to volume with distilled water. This solution is equivalent to 57.2% 
phosphoric acid.  
 
4 ppm Working Standard: Pipette a 4- mL aliquot of the phosphate stock solution into a 200- mL 
volumetric flask and dilute to vo lume with distilled water. This solution is equiva lent to 45.8% 
phosphoric acid.  
 Blank Working Solution: Boil a mixture consisting of 5 ml of HCl and 30 ml of HNO
3 until brown 
fumes have been expelled, transfer to a 500- ml volumetric flask and dilute to vo lume with distilled 
water. Transfer a 4- ml aliqu ot to a 200- ml volumetric flask and dilute to volume with distilled water.  
 
A.4 Preparation of colo ur development solutions  
 
Acid Molybdate Solution:  Pour, with stirring, a solution containing 16.62 g of a mmonium molybdate 
in 156.9 ml of distilled water i nto a solution of 318.4 ml of HCl to which 29.6 ml of distilled water has 
been added.  
 Reducing Solution: Dissolve 1.0 g of p- methylaminophenol sulfate and 3.0 g of sodium acid sulfite in 
100 ml distilled wa ter.  
 PUBLIC REVIEW DRAFTARS 14 82:2020  
6 © ARSO 20 20 — All rights reserved A.5 Procedure  
 
Weigh, to the nearest 0.1 mg, 0.50 ± 0.02 g of sample into a 500- ml volumetric flask, adding 30 ml of 
HNO 3 and 5 ml of HCl. Boil until brown fumes have been expelled, cool to room temperature and 
dilute to volume with distilled water.  Transfer a 2- ml aliquot to a 100- ml volumetric flask and dilute to 
volume with distill ed water. From this second dilution, transfer a 10- ml aliquot to a 20- ml scintillation 
vial and add a 2- ml aliquot of acid molybdate solution and a 2- ml aliquot of red ucing solution. Allow to 
stand 1 hour for colou r development. At the same time that the sample vial is prepared, a blank vial, a 
4 ppm phosphorus vial and a 5 ppm phosphorus vial must also be prepared and allowed to develop 
colour along with the sample. The blank, 4 ppm phosphorus and 5 ppm phosphorus are p repared by 
the same procedure used for preparation of the sample, using 10- ml aliquots of the blank working 
solution, the 4 ppm phosphorus working standard and the 5 ppm phosphorus working standard.  
 
NOT E When making determinations on fertilizers with l ow percentages of phosphoric acid, it is necessary to adjust the 
sample weight so that the sample working dilution contains between 4 ppm and 5 ppm phosphorus.  
 Calibrate the instrument using the blank soluti on, the 4 ppm phosphorus solution and the 5 ppm 
phosphorus solution, then determine the concentration of the sample solution.  
 
NOTE  When using an Atomic Absorption Spectrophotometer for colou r measurements, the cuvet holder is placed over the 
burner in t he light path and a Cu hollow cathode lamp is used w ith the instrument grating set at a wavelength of 640 nm.  
 A.6 Calculations  
 The method of calculating the  % phosphoric acid will vary according to the make and model of 
instrument used. Report the result s to the nearest 0.1% P
2O5 as follows:  
 
% Phosphori c Acid (P 2O5)  
 
 PUBLIC REVIEW DRAFTARS 14 82:2020  
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Bibliography  
 
 
Working Group to identify and acknowledge useful literature used in the preparation of this standard.  
 KS 46:2011, Granulated superphosphate fertilizer — Specification  
  
 
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