PUBLIC REVIEW DRAFT DRAFT UGANDA STANDARD  
  DUS DEAS 912 
First  Edition  
2018-mm-dd 
 
 Reference number  
DUS DEAS 912: 2018 
© UNBS 201 8 
  
Fertilizer — Nitrogen, Phosphorus & Potassium (NPK) 
compound ― Specification  
 PUBLIC REVIEW DRAFTDUS DEAS 912: 2018 
ii                © UNBS  2018 - All rights reserved 
 Compliance with this standard does not, of itself confer immunity from legal obligations  
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2018 
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 PUBLIC REVIEW DRAFTDUS DEAS 912:2018 
© UNBS  2018 - All rights reserved                iii National foreword 
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 Uganda, as amended.  UNBS is mandated to co-
ordinate the elaboration of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex Alimentarius Commission on Food Standards, and  
(c) the National 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 consists 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 reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
This Draft Uganda Standard, DUS DEAS 912: 2018, Fertilizer — Nitrogen, Phosphorus & Potassium (NPK) 
compound  ― Specificati on, is identical with  and has been reproduced from a Draft East African Standard, 
DEAS 912 : 2018, Fertilizer — Nitrogen, Phosphorus & Potassium (NPK) compound  ― Specification , and is 
being proposed for adoption as a Uganda Standard. 
This standard was developed by the Food and agriculture  Standards Technical Committee (UNBS/TC 2). 
Wherever the words, “ East African Standard" appear, they should be replaced by "Uganda Standard." 
 
  PUBLIC REVIEW DRAFT DEAS 91 2:2018  
 
© EAS 2018                                                                                                               First Edition 201 8 
 
 
DRAFT EAST AFRICAN STANDARD  
Fertilizer — Nitrogen, Phosphorus & Potassium (NPK) 
compound — Specification  
EAST AFRICAN COMMUNITY  PUBLIC REVIEW DRAFTPUBLIC REVIEW DRAFT   
 
 
  
 Foreword  
Development of the East African Standards has been necessitated by the need for harmonizing requirements 
governing qu ality of products and services in the East African Community. It is envisaged that through 
harmonized standardization, trade barriers that are encountered when goods and services are exchanged 
within the Community will be removed.  
In order to achieve this  objective, the Community established an East African Standards Committee mandated 
to develop and issue East African Standards.   
The Committee is composed of representatives of the National Standards Bodies in Partner States, together 
with the representati ves from the private sectors and consumer organizations. Draft East African Standards 
are circulated to stakeholders through the National Standards Bodies in the Partner States. The comments 
received are discussed and incorporated before finalization of st andards, in accordance with the procedures 
of the Community.  
East African Standards are subject to review, to keep pace with technological advances. Users of the East 
African Standards are therefore expected to ensure that they always have the latest versi ons of the standards 
they are implementing .  PUBLIC REVIEW DRAFT 
© EAC 2018 – All rights reserved  Fertilizer – Nitrogen, Phosphorus & Potassium (NPK) 
compound – Specification  
1 Scope  
This Draft East African  Standard specifies  requirements and methods of sampling and test for NPK fertilizer 
(compound and ble nded)  
2 Normative References  
The following referenced standards are indispensable for the application of this standard. For dated 
references, only the edition cited applies. For undated references, the latest edition of the referenced standard 
(including a ny amendments) applies:  
ISO 8157 , Fertilizers and Soil Conditioners – Vocabulary  
DEAS 913 , Fertilizer – Methods of sampling  
ISO 17318 , Fertilizers and soil conditioners -- Determination of arsenic, cadmium, chromium, lead and 
mercury contents  
ISO 8397 , Solid fertilizers and soil conditioners  – Test sieving  
AOAC  937.02 , Magnesium (Water -Soluble) in Fertilizers  
AOAC 967.01, Iron in fertilizers. Titrimetric method  
AOAC 973.01, Zinc in fertilizers. Zinc ion exchange method  
AOAC 972.03, Manganese (Water -soluble)  in fertilizers  
3 Terms and Definition  
For the purpose of this Tanzania standard, terms and definition given in ISO 8157  shall apply.  
4 Requirements  
4.1 General requirements  
4.1.1  Description  
NPK fertilizer shall be  inorganic fertilizer containing Nitrogen , Phosphorus & Potassium which may be in 
granular, prilled or crystalline forms. It shall be free from any foreign matter. The granules shall be smooth, 
free flowing and of uniform  colour. NPK fertilizers may contain other micro and secondary nutrients.  
4.1.2 Particle size  
The particle size of the granular material, shall be such that not less than 90 per cent by mass of fertilizer, 
shall be of particles size range of 2 mm – 5 mm and for prilled material shall be of particles s ize range of 1mm 
- 4mm when  tested by the method given in ISO 8397  PUBLIC REVIEW DRAFT 
  4.2 Specific requirements  
4.2.1  NPK fertilizer shall have a moisture content of not more than 1 % w/w maximum  when tested in 
accordance with Annex A. 
4.2.2  A compound fertilizer shall contain two or more of the followin g primary plant nutrient elements 
intended for fertilizing of crops: nitrogen (N), phosphorus (P) and potassium (K).  The lower limit of the 
declared value of any of the primary nutrients shall comply with the tolerances depending on the amount of 
Primary nutrient guaranteed as 1%  when tested in accordance with ISO 5315.   
4.2.3  Besides the primary nutrient elements, the fertilizer may also contain one or more of the following 
elements: Sulphur, Calcium, Magnesium, Boron, Cobalt, Copper, Iron, Manganese, Mo lybdenum, and Zinc, 
which, when present for the purpose of fertilizing of crops and mentioned in any form or manner, shall be 
guaranteed on the elemental basis.  Sources of the elements guaranteed and proof of availability shall be 
provided upon request.  The elements shall be mentioned and guaranteed if their percentage values by mass 
are equal to or more than the values shown in Table 1  
Table 1— Minimum percentage for guarantee  
Element  % 
Sulphur  (S) 1.00 
Calcium  (Ca) 1.00 
Magnesium (Mg)  0.60 
Copper  (Cu) 0.05 
Iron (Fe)  0.10 
Manganese (Mn)  0.050  
Molybdenum (Mo)  0.0005  
Zinc (Zn)  0.05 
5 Contaminants  
Heavy metal contaminants in NPK fertilizer  shall conform to the  limits given in Table 2 when tested with the 
method specified therein.  PUBLIC REVIEW DRAFT 
© EAC 2018 – All rights reserved   
Table 2 — Requir ements for heavy metal contaminants  
Heavy metal  Requirement  Method of test  
Arsenic , mg/kg, max  20 
ISO 17318  Cadmium , mg/kg, max.  60 
Mercury , mg/kg, max  0.1 
Lead , mg/kg, max.  30 
Chromium , mg/kg, max.  500 
  
6 Sampling and testing  
6.1 Sampling  
Sampl ing of NPK fertilizer shall be done as prescribed in DEAS 913.  
6.2 Testing  
Testing of NPK fertilizer shall be done as prescribed in the referenced standards and  annex  within this 
standard . 
7 Packaging and labelling  
7.1 Packaging  
The fertilizer shall be pac kaged in materials that are clean and non -defective that protect s the product from 
physical, chemical and moisture contamination and withstand multiple stages of handling (transportation and 
storage).  
7.2 Labelling  
Each package shall be indelibly labeled i n English and/or any other language with the following information:  
a) name of the fertilizer i.e. "Nitrog en Phosphorus Potassium (NPK)"  
b) name and address of the manufacturer/pa cker and importer/ distributor  
c) NPK Grade  
d) net content by mass  in kg;  
e) country of ori gin;  
f) handling instructions including the words “Use No Hooks” ; 
g) production date and expiry date ; 
h) batch number ; and  
i) storage conditions . PUBLIC REVIEW DRAFT 
  Annex A 
(normative)  
 
Determination of moisture content  
A.1 Oven dry method  
A.1.1  General  
The method does not apply to fer tilizers that yield volatile substances other than water at drying temperature.  
A.1.2  Procedure  
A.1.2.1  Weigh accurately 2 g of the prepared sample in a pre -weighed, clean and dry weighing bottle or 
petridish.  
A.1.2.2  Heat in an oven for about 5 hours at 1 05  C + 2  C to constant weight. Cool in a desiccator and 
weigh. For urea, heat at 70  C + 5  C  for five hours to constant weight.  
A.1.3  Calculation  
Moisture per cent by weight (%) =  
ABCB

100  
where,  
A is the weight in gram of the empty bott le; 
B is the weight of the bottle plus the material in gram, before drying;  
C is the weight of the bottle plus the material in gram, after drying . 
A.2 Vacuum desiccator method  
A.2.1  General  
The method is applicable to Ammonium Chloride, Calcium Ammonium Ni trate (CAN), Di -Ammonium 
Phosphate (DAP) and all types of complex and mixtures of NPK fertilizers.  
A.2.2 Procedure  
Weigh accurately in duplicate 5g of prepared sample in a weighed shallow porcelain dish. Put the sample in a 
desiccator over concentrated sul phuric acid, close and introduce vacuum for about 10 minutes, then stop the 
vacuum pump and leave the sample for 24 hours, then release vacuum, remove the sample from the 
desiccator and weigh.  
A.2.3 Calculation  
Moisture per cent by weight = 
) () (
100
1 23 2
W WW W

  
where,  
W1 is the Weight in gram of empty porcelain dish ; PUBLIC REVIEW DRAFT 
© EAC 2018 – All rights reserved  W2 is the Weight in gram of porcelain dish with sample before putting the sample for 24 hours in the 
desiccator ; 
W3 is the Weight in gram of porcelain dish with sample after putting the samp le for 24 hours in the 
desiccator . 
A.3 Karl Fischer method  
A.3.1  General  
This method is applicable to fertilizers like CAN, Urea and urea based complexes. This method is not suitable 
for phosphate rock based fertilizers and fertilizers containing monocalci um phosphate, calcium sulphate, alkali 
carbonates as well as aldehydes and ketone groups.  
A.3.2  Apparatus  
Karl Fischer titrator  
A.3.3  Reagents  
A.3.3.1  Karl Fischer reagent  (KF) – Karl Fischer solution (pyridine free) (single solution) . 
A.3.3.2  Di-sodium ta rtarate dihydrate (Na 2C4O62H2O) analytical grade  
A.3.3.3  Methanol -KF grade/spectroscopy grade containing less than 0.05 % water . 
A.3.4  Procedure  
A.3.4.1  Standardization of KF reagent.  
A.3.4.1.1  Set up the instrument as per manufacturer’s manual.  
A.3.4.1.2  Add methanol to the titration vessel until the electrodes are dipped and titrate with Karl -Fischer 
reagent to a pre -set end point persists for 30 seconds.  
A.3.4.1.3  Add 100mg of the disodium tartarate dehydrate to the titration vessel carefully and titrat e with Karl 
Fischer reagent to a pre -set end point (the pre -set end point should persist for 30 seconds). Note the volume 
of KF reagent used as V 1 ml. 
A.3.4.2  Determination of moisture of sample  
A.3.4.2.1  Weigh accurately 1 g of the prepared sample and tra nsfer to the titration vessel carefully and stir 
until dispersed.  
 
A.3.4.2.2  Titrate with KF reagent to the same pre -set end point as above and note the volume of KF 
reagent used as V 2 ml. 
A.3.5  Calculation  
Factor (F)(mgH 2O/1 ml of KF reagent ) = 
1added dihy drate tartarate sodiumofmg 0.1566
V  
Moisture per cent by weight = 
0001 (gram) sampleof Weight100 2
VF