UGANDA STANDARD  
  DUS 2078  
First Edition  
2018 -mm-dd 
 
 
 Reference number  
DUS 2078 : 2018 
© UNBS 2018   
  
Organic -inorganic compound fertilizer — Specification   
 DUS 2078 : 2018  
ii © UNBS 2018 – All rights reserved  
 Compliance with this standard does not, of itself confer immunity from legal obligations  
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. DUS 2078:2018  
© UNBS 2018 – All rights reserved  iii 
 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 T BT 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 key stakeholder s 
including government, academia, consumer groups, private sector and other interested parties.  
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.  
The committee responsible for this document is Technical Committee UNBS /TC 2, Food and Agriculture 
Subcommittee SC 20, Agro chemicals and veterinary drugs . 
. DUS 2078 : 2018  
iv © UNBS 2018 – All rights reserved  
 UGANDA STANDARD  DUS 2078: 2018  
 
© UNBS 2018 – All rights reserved  1 
 Organic  — Inorganic compound fertilizer  — Specification  
1 Scope   
This Draft Uganda standard  specifies the requirements, sampling and test methods of organic  – Inorganic 
compound  fertilizers  
2 Normative references   
The fo llowing referenced documents referred to in the text in such a way that some or all of their content 
constitutes requirements of this document. For dated references, only the edition cited applies. For undated 
references, the latest edition of the referenc ed document (including any amendments) applies.  
US ISO 10390,  Soil quality — Determination of pH  
ISO 17184: Soil quality -- Determination of carbon and nitrogen by near -infrared spectrometry (NIRS ) 
ISO 8157, Fertilizers and soil conditioners -- Vocabulary  
US ISO 11261, Soil quality — Determination of total nitrogen — Modified Kjeldahl method  
US ISO 10694, Soil quality — Determination of organic an d total carbon after dry combustion (elementary 
analysis)  
US ISO 11261, Soil quality — Determination of total nitrogen — Modified Kjeldahl method  
US ISO 6598, Fertilizers — Determination of phosphorus content — Quinoline phosphomolybdate gravimetric 
method  
US ISO 8397 , Solid fertilizers and soil conditioners — Test sieving  
US ISO 11265, Soil quality — Determination of the specific electrical conductivity  
US ISO 17318, Fertilizers and soil conditioners — Determination of arsenic, cadmium, chromium, lead and 
mercury contents  
US ISO 11047, Soil quality — Determination of cadmium, chromium, cobalt, copper, lead, manganese, nickel 
and zinc in aqua regia extracts of soil — Flame and electrothermal atomic absorption spectrometric methods . 
US ISO 725, Microbiology of food and animal feeding stu ffs — Horizontal method for the detection and 
enumeration of presumptive Escherichia coli — Most probable number technique  
US ISO 6579 –1, Microbiology of the food chain — Horizontal method for the detection, enumeration and 
serotyping of Salmonella — Part 1: Detection of Salmonella spp.  
DUS ISO 7899 -1, Water quality -- Detection and enumeration of intestinal enterococci -- Part 1: Miniaturized 
method (Most Probable Number) for surface and waste water   
2 © UNBS 2018 – All rights reserved  
 US ISO 9308 -2, Water quality — Enumeration of Escherichia  coli and coliform bacteria — Part 2: Most 
Probable Number method (2nd Edition)  
US ISO 7409 , Fertilizers  -- Marking -- Presentation and declarations  
US ISO 8397 : Solid fertilizers and soil conditioners — Test sieving  
3 Terms and definitions   
For the purpos es of this document, the terms and definitions given in DUS ISO 8157  and the following apply.  
ISO and IEC maintain terminological databases for use in standardization at the following addresses:  
— ISO Online browsing platform: available at http://www.iso .org/obp  
3.1  
fertilizer  
materials with the main function of providing plant nutrients  
3.2 
Inorganic (mineral) Fertilizer  
Fertilizer that indicates an inorganic salt form of nutrients, and it is made from extraction, physical and/or 
chemical industrial met hods.  
3.3 
Organic Fertilizer  
material containing carbon or one or more elements other than hydrogen and oxygen, mainly of plant and/or 
animal origin added either directly to the plant or to the soil, specifically, for the nutrition of plants and that may 
improve soil structure  
3.4 
Compound Fertilizer  
fertilizer having a declarable content of at least two of the primary plant nutrients (nitrogen, phosphorus, and 
potassium), obtained chemically or by blending, or both, including NP, NK, PK, and NPK product  
3.5 
Organic -inorganic compound fertilizer  
Compound fertilizer with certain amount of organic fertilizer.  
3.6 
Total primary nutrient  
The sum of total nitrogen, effective phosphorus pentoxide, and potassium oxide calculated  according to mass 
fraction.  
4 Requirements  
4.1 General requirement  
4.1.1 Organic – inorganic compound fertilizer shall have the a ppearance  granular or strip products, without 
mechanical impurities.  
4.1.2  Organic - inorganic fertilizer shall be free from foul smell.  
4.1.3 Organic – inorganic fertilizer shall be homogenous in texture.  DUS  2078: 2018  
© UNBS 2018  – All rights reserved  3 
 4.1.4  The product shall be free from contaminants which include but not limited to residual hormones, 
antibiotics, pesticides and pathogens . 
4.1.5  4.1.2  The particle size of the granular material, shall be such that not less than 90 % by mass of 
fertilizer, shall be of particles size range of 2 mm – 5 mm and for prilled material shall be of particles size 
range of 1mm - 4mm when tested in accordance with US ISO 8397  
4.2 Specific requirements  
4.2.1  Organic -inorganic compound fertilizer shall conform to the requirements in Table 1  
Table 1: Specific requirements for Organic - inorganic compound fertilizers  
Parameter  Limit  Method of test  
pH 5.5 – 8.0 US ISO 10390  
Carbon: Nitro gen ratio,  Max 20:1 DUS ISO 17184  
Moisture content, %, m/m  check alternative method  10-35 Annex A  
Total Nitrogen, %, m/m, min.  1 US ISO 11261  
Organic carbon, %, m/m, min.  6 US ISO 10694  
Organic matter content (solid),  %, m/m, min.  12 Annex B  
Total primary nutrients — N-P2O5-K2O (solid and liquid 
organic fertilizer),%, m/m, min  15 
 US ISO 11261, US 
ISO 6598  
Foreign matter > 2 mm, % m/m, max  0.5 US ISO 8397  
Soluble salts (conductivi ty), mmhos, max.  5 US ISO 11265  
* For pelletized fer tilizer, moisture content shall  be ≤10%.  
 
4.2.2  Content of the identified single nutrient shall n ot be less than 3.0%,  
5 Heavy metal contaminants  
Heavy metal contaminants in the fertilizers shall conform to the limits gi ven in Table 2 when tested with the 
method specified therein   
Table 2— Heavy metal contaminant limit s for organic - inorganic compound  fertilizers  
Properties  Allowable maximum level 
(mg/kg, dry weight)  Test method  
Arsenic (As)  10 US ISO 17318  
Lead (Pb)  30  US ISO 17318  
Chromium (Cr)  50 US ISO 17318  
Nickel (Ni)  50 US ISO 11047  
Mercury (Hg)  2 US ISO 17318  
Cadmium (Cd)  5 US ISO 17318  
  
4 © UNBS 2018 – All rights reserved  
 6 Hygiene  
Organic - inorganic compound fertilizers  shall be free from pathogenic organisms. The product shall comply 
with microbiological limits in the following table:  
 
Table 3 — Microbiological limits for organic fert ilizers  
 
Microorganisms  Allowable level  Method of test  
E. coli absent  US ISO 7251  
Salmonella spp  Absent in 25 g  US ISO 6579 –1 
Faecal streptococci  <500 cfu/g  DUS ISO 7899 -1 
Total coliforms  100 cfu/g  US ISO 9308 -2 
 
7 Sampling  
 
7.1 Sampling for laborato ry analysis  
 
All finished products should be subjected to lot sampling for laboratory analysis using the following procedure:  
 
For composite sampling of solid products:  
 
(1) Present to the inspector the production documents containing the number of bags pe r batch number 
and bag number.  
 
(2) The inspector will randomly select the bag number.  
 
(3) The selected bags will be emptied into a clean area. All contents of the selected bags) will be 
thoroughly mixed.  
 
(4) Submit five kilograms (5 kg) of the composite  sample to the laboratory.  
 
(5) Information r elative to the sample taken shall  be accurate and complete to allow traceability of the 
sample back to the lot from which it was sampled.  
 
NOTE  If the samples analyzed do not conform to the standards, the inspec ting Certifying Body (CB) should review the production 
process which may include bulk sampling.  
 
Table 6 — Required Number of Samples for Solid Products  
 
Number of bags* per batch  Bags to be sampled  
<50 2 
51 to 100  3 
101 to 300  8 
301 to 500  15 
501 to 1000  20 
More than 1000  Multiples of 20  
* NOTE  1 bag = 50 kg  
 
For composite sampling of liquid products:  DUS  2078: 2018  
© UNBS 2018  – All rights reserved  5 
  
(1) Present to the inspector the production documents containing the number of containers per batch 
number and container number.  
 
(2) The inspector will randomly select the container number and subject the selected containers for 
analysis.  
 
(3) Information related to the sample taken must be accurate and complete to allow traceability of the 
sample back to the lot from which it was sampled.  
 
Table 7 — Required number of samples for liquid products  
 
Number of containers* per batch  Containers to be sampled  
≤ 50 1 
51 to 100  2 
101 to 300  3 
301 to 500  4 
More than 500  5 
*NOTE: 1 container should be at least 1 L  
 
7.2 Laboratory sampling (sample preparation for laboratory analysis)  
(a) For samples with uniform fineness  
 
Place sample on a clean smooth flat su rface and mix thoroughly. Reduce sample to a quantity sufficient for 
analysis by quartering. Mix and store in air -tight container.  
 
(b) For liquid fertilizers  
 
For liquid fertilizers without suspended particles, stir the sample until it is thoroughly mixed  before taking a 
sample.  
 
For liquid fertilizers with suspended particles, take a sample while mixing the material in order to obtain a 
representative sample.  
 
8 Packaging  and storage  
8.1 The Organic - inorganic compound  fertiliz er shall be packed in clean,  non-defective and strong 
containers.   
8.2 The material for which the container is made shall be such as to protect the contents from moisture 
and also not lead to easy rupture during handling, transportation and storage.  
8.3 The products should be stored in a cool and dry place and should be protected from rain, moisture, 
sun protection and rupture  
9 Labelling  
 
9.1 Each container of the Organic – inorganic compound fertiliser shall bear a label in indelible marking in 
accordance with US ISO 7409, ) and with the following particulars:  
 
a) Product name as “Organic - inorganic compound  fertilizer   
6 © UNBS 2018 – All rights reserved  
 b) Nutrient content(N PK) 
c) Carbon/Nitrogen ratio  
d) Organic matter content  
e) Moisture content  
f) Batch number  
g) Percentage foreign matter ( Name and physical address of the manufacturer/packer/importer  
h) Date of manufacture  
i) Best before date  
j) Instructions for use  
k) Precautions /warnings  
l) Country of origin  
m) net content  
n) registration number  
o) form of product  
 
9.2 Where the fertilizer is distr ibuted in bulk, the labelling  information shall accompany the delivery notice to 
the purchaser.  
 DUS  2078: 2018  
© UNBS 2018  – All rights reserved  7 
 Annex A  
(normative)  
 
Determination of moisture content  
A.1 Oven dry method  
A.1.1 General  
The method does not apply to fertilizers 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 105 + 2 C to constant weight. Cool in a desiccator and 
weigh. For urea, heat at 70 + 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 bottle ; 
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  Genaral  
The method is applicable to Ammonium Chloride, Calcium Ammonium Nitrate (CAN), Di -Ammonium 
Phosphate (DAP)  and all types of complex and mixtures of NPK fertilizers.  
A.2.2 Procedure  
Weigh accurately in duplicate 5  g of prepared sample in a weighed shallow porcelain dish. Put the sample in a 
desiccator over concentrated sulphuric acid, close and introduce vacu um 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.   
8 © UNBS 2018 – All rights reserved  
 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 ; 
W2 is the weight in gram of porcelain dish with sample before putting the sample for 24 hours in the 
desiccator ; and 
W3 is the weight in g ram of porcelain dish with sample after putting the sample 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 monocalcium 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 tartarate dihydrate  (Na2C4O62H2O) analytical grade  
A.3.3.3  Methanol -KF grade/spectroscopy grade  containing less than 0.05 % water   
A.3.4  Procedure  
Standardization of KF reagent.  
a) Set up t he instrument as per manufacturer’s manual.  
b) 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.  
c) Add 100mg of the disodium tartarate dehydrate to the titration vessel carefully and titrate 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.4 Determination of moisture of sample  
A.4.1  Weigh ac curately 1 g of the prepared sample and transfer to the titration vessel carefully and stir until 
dispersed.  
A.4.2  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. DUS  2078: 2018  
© UNBS 2018  – All rights reserved  9 
 A.5 Calculation  
Factor (F)  (mgH 2O/1 ml of KF reagent )  = 
1added dihydrate tartarate sodiumofmg 0.1566
V  
Moisture per cent by weight = 
0001 (gram) sampleof Weight100 2
VF  
 
Annex B  
(Normative)  
Determination of Content of Organic Matter (Potassium Dichromate Volumetric 
Method)  
B.1 Method and Principle  
The quantitative potassium dichromate - sulfuric acid solution is used to oxidize the organic carbon in the 
organic fertilizer under heating. Excess potassium dichromat e is titrated with ferrous sulfate standard solution; 
meanwhile, the blank test is carried out by using the silicon dioxide as the additive. The content of organic 
carbon shall be calculated based on the consumption of oxidants before and after oxidation a nd the value 
obtained is multiplied by a factor of 1.724 to obtain the content of organic matter  
B.1.2 Instruments and Equipment  
The common laboratory instruments and equipment shall be used.  
B.1.3 Reagents and Preparation  
Silicon dioxide: in powder form.  
Sulfuric acid ( ρ1.84).  
K2Cr2O7 c(1/6 K 2Cr2O7)=0.1mol/L 。 
Potassium dichromate (K 2Cr2O7) standard solution: c(1/6 K 2Cr2O7)=0.1mol/L .。 
Weigh out 4.9031g potassium dichromate (primary  reagent) after drying for 3h~4h at 130°C and dissolve it 
with a small amount of water, and then transfer the potassium dichromate solution to a 1L volumetric flask and 
dilute the solution with water to the scale mark and shake well.  
c(1/6  K2Cr2O7)=0.8mol/L 。 
Potassium dichromate solution: c(1/6  K2Cr2O7)=0.8mol/L.  
Weigh out 39.23g  potassium dichromate (analytically pure) and dissolve it with a small amount of water, and 
then transfer th e potassium dichromate solution to a 1L volumetric flask and dilute the solution to the scale 
mark and shake well.  
FeSO 4）：c(FeSO 4)=0.2mol/L 。 
Ferrous sulfate (FeSO 4) standard solution: c(FeSO 4)=0.2mol/L.   
10 © UNBS 2018 – All rights reserved  
 Weigh out 55.6g FeSO 4·7H 2O (analytically pure), dissolve it in 900mL water and dissolve the solution by 
adding 20mL sulfuric acid (5.2.3.2), dilute it to the constant  volume of 1L, and shake well (if necessary, filter 
it). The accurate concentration of the solution is calibrated based on 0.1mol/L potassium dichromate standard 
solution (5.2.3.3) and it shall be calibrated for immediate use.  
Calibration of c(FeSO 4)=0.2mol/L standard solution: pipette 20.00mL potassium dichromate standard solution 
(5.2.3.3) into a 15 0mL triangular flask, add 3mL~5mL sulfuric acid (5.2.3.2) and 2~3 drops of o -
Phenanthroline indicator (5.2.3.6), and titrate it with ferrous sulfate standard solution (5.2.3.5). The accurate 
concentration  c1 is calculated by equation (1) based on the consu mption of ferrous sulfate standard solution in 
the titration . 
 
 
Where:  
c1——Concentration of potassium dichromate standard solution, in mol/L;  
V1——Volume of potassium dichromate standard solution pipetted, in mL;  
V2——Volume of ferrous sulfate standard solution consumed in the titration, in mL.  
Phenanthroline indicator  
Weigh out 0.695g ferrous sulfate (analytically pure) and 1.485g o -Phenanthroline (analytically pure), dissolve 
them in 100mL water, and shake well. The indicator is easy to deteriorate, so it shall be stored in a closed 
brown bottle.  
B.1.5  Determination Steps  
Weigh out 0.2g~0.5g air -dried sample (accurate to 0.0001g) after sieving with a Φ1mm sieve, put it in a 
500mL triangular flask, accurately add 50.0mL potassium dichromate solution of 0.8mol /L (5.2.3.4) and 
50.0mL concentrated sulfuric acid (5.2.3.2), and place a small bent neck funnel in boiling water and keep it for 
30min after the water is boiled. Take it out of the boiling water and cool it to the room temperature, flush the 
small funnel with water and collect the washing liquor into the triangular flask. Take off the triangular flask, 
transfer intact the reactant to a 250mL volumetric flask, cool it to the room temperature, and dilute it to the 
constant volume; pipette 50.0mL solution int o a 250mL triangular flask, add water to about 100mL, and add 
2~3 drops of o -Phenanthroline indicator (5.2.3.6). When the solution is titrated with 0.2mol/L ferrous sulfate 
standard solution (5.2.3.5) near the end point, the solution changes from green to dark green, and then the 
ferrous sulfate standard solution is added dropwise until the brick red is generated. Meanwhile, weigh out 0.2g 
silicon dioxide (accurate to 0.001g) (5.2.3.1) to replace the sample, and conduct the blank test with the same 
reagents  by using the same analysis steps.  
If the amount of ferrous sulfate standard solution used in the titration of the sample is less than one -third of the 
amount of ferrous sulfate standard solution use d in the blank test, the sample weight shall be reduced and re -
determined.  
B.1.6 Expression of Analysis Results  
The content of organic matter is expressed as the mass fraction of fertilizer and is calculated by equati on (2) 
below:  
 DUS  2078: 2018  
© UNBS 2018  – All rights reserved  11 
 Where:  
 
c——Molar concentration of ferrous sulfate standard solution, in mol/L;  
 
V0——Volume of ferrous sulfate standard solution consumed in the blank test, in mL;  
V——Volume of ferrous sulfate standard solution consumed in the sample determination, in mL;  
0.003——Molar mass of one -fourth of a carbon atom, in g/mol;  
1.724——Factor for c onverting the organic carbon to the organic matter;  
1.5——Oxidation correction factor;  
m——Mass of air -dried sample, in g;  
X0——Moisture percentage of air -dried sample;  
D——Taking multiple, c onstant volume/taking volume, 250/50.  
  
12 © UNBS 2018 – All rights reserved  
 Bibliography  
[1] China  standard for Organic - inorganic compound fertilizer  
[2] ARSO standards for organic fertilizer  
 DUS 2078: 2018  
© UNBS 2018 – All rights reserved  13 
 Certification marking  
Products that conf orm to Uganda standards may be marked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below.  
The use of the UNBS Certification Mark is governed by the Standards Act, and the Regulations made 
thereunder. This mark can  be used only by those licensed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in conjunction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation to a product is an assurance  that the goods comply with the 
requirements of that standard under a system of supervision, control and testing in accordance with the 
certification mark scheme of the Uganda National Bureau of Standards. UNBS marked products are 
continually checked by UN BS for conformity to that standard.  
Further particulars of the terms and conditions of licensing may be obtained from the Director, Uganda 
National Bureau of Standards.  
 
 DUS 2078 : 2018    
 
ICS 65.080  
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