UGANDA STANDARD  
  DUS 2081  
First  Edition  
2018 -mm-dd 
 
 
 Reference number  
DUS 2081 : 2018 
© UNBS 2018   
  
Compound microbial fertilizers — Specification   
 DUS 2081: 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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permission from UNBS.  
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The Executive Director  
Uganda National Bureau of Standards  
P.O. Box 6329  
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Uganda  
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 DUS 2081: 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 m andated 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  Agreem ent 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 stakeholders 
includi ng 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, Agrochemical s and veterinary drugs . 
 UGANDA STANDARD  DUS 2081: 2018  
 
© UNBS 2018  – All rights reserved  1 
 Compound microbial fertilizer  — Specification   
1 Scope   
This Draft Uganda Standard specifies requirements and meth ods of sampling and test for compound microbial 
fertilizers . 
2 Normative references   
The following referenced docume nts 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 referenced document (including an y amendments) applies.  
US ISO 8157,  Fertilizers and soil conditioners – Vocabulary  
US ISO 7409  Fertilizers — Marking — Presentation and declarations  
US ISO 11261, Soil quality — Determination of total nitrogen — Modified Kjeldahl method  
US ISO 6598, Fertil izers  — Determination of phosphorus content — Quinoline phosphomolybdate gravimetric 
method  
US ISO 17319 , Fertilizers and soil conditioners -- Determination of water -soluble potassium content -- 
Potassium tetraphenylborate gravimetric method.  
US ISO 11465 , Soil quality — Determination of dry matter and water content on a mass basis — Gravimetric 
method  
US ISO 10390 , Soil quality — Determination of pH  
US ISO 9308 -2, Water quality — Enumeration of Escherichia coli and coliform bacteria — Part 2: Most 
Probable  Number method (2nd Edition)  
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.  
US ISO/TS 21872 -1, Microbiology of food and animal feeding stu ffs – Horizontal method for the detection of 
potentially enteropathogenic Vibrio spp. – Part 1: Detection of Vibrio parahaemolyticus and Vibrio cholera  
DUS ISO 21567 Microbiology of food and animal feeding stuffs -- Horizontal method for the detection of 
Shigella spp.  
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   
2 © UNBS 2018  – All rights reserved  
 3 Terms and definitions   
For the purposes of this document, the terms and definitions given in DUS ISO 8157 apply.  
ISO and IEC maintain terminological databases for u se in standardization at the following addresses:  
— ISO Online browsing platform: available at http://www.iso.org/obp  
3.1  
Compound microbial fertilizer  
active microbial product composed of specific microbes and nutrient substances, developed to provide, 
maintain and improve nutrition to plants.  
3.2 
Total Primary Nutrient  
sum of content of total nitrogen, effective phosphorous pentoxide and potassium oxide, measured in mass 
fraction.  
4 Requirements  
4.1 General requirements  
4.1.1  The base or carrier materi al used in the manufacture of compound microbial fertilizer may be either 
solid or liquid, be free from contamination and appropriate for the intended purpose . 
4.1.2  The compound microbial fertilizer shall be presented in an appropriate form to aid its app lication. It 
may be in the form of dry powder, granules or liquid.  There shall be no excessive precipitation for liquid 
products. The precipitation shall disperse evenly after shaking.  Solid products  shall pass through a 0.15 -mm – 
0.212 -mm (150 -μ – 212-μ) sieve.  
4.1.3  The compound microbial fertilizer shall not contain substances that are likely to be detrimental or 
injurious to vegetation, animals, public health or the environment when used according to the directions 
provided by the manufacturer.  
4.1.4  The compound microbial fertilizer shall not contain substances that would, when applied in amounts 
commonly used or as specified in the directions for use, leave in the tissues of a plant a residue of a 
poisonous or harmful substance.  
4.1.5   Its already cove red in the regulation  
4.2 Specific requirements  
4.2.1  Compound microbial fertilizers shall comply with the specific requirements stipulated in Table 1  
Table 1   Specific requirements for compound microbial fertilizers  
Characteristic  Allowable limit  Test Me thod 
Liquid  solid 
Total primary nutrient (N+P2O5 + K2O)  % 6.0 – 20.0 8.0 – 25.0 US ISO 11261, US ISO 
6598 , US ISO 17319  
Number of active microbes (cfu) a 
hundred million/g (mL), Min  0.50 0.20 Annex A  
Organic matter (in dry basis) % Min  - 20.0 Annex C  
Moisture % Max  - 30 US ISO 11465  
pH 5.5 – 8.5 US ISO 10390  
Period of validity, Months, Min  3 6 - 
 DUS 2081: 2018  
© UNBS 2018  – All rights reserved  3 
 4.2.2 For compound microbial fertilizers containing two or more types of effective microbes, the number of 
each type shall not be less than 1 million/ gr am (mL)  
4.2.3  Total primary nutrient shall be within the limits specified in table 1. The absolute value of positive and 
negative deviation between the indicated and estimated  value shall not be more than 2.0%. The proportion of 
each primary nutrient  in the total primary nutrient should be not less than 15%.  
5 Hygiene  
5.1 Compound microbial fertilizers shall be produced and handled under hygienic conditions and in 
appropriate premises in order to prevent contamination of the product.  
5.2 Compound microbial fertilizers shall comply with the limits for micro -organisms specified in Table 2.  
Table 2: Microbial limits for Compound microbial fertilizers  
Organism  Limit  Test method  
Faecal coliforms per g (mL) max  100 US ISO 9308 -2 
Mortality of ascarid egg % min  95 Annex B  
Salmonella  Absent  US ISO 6579 –1 
Shigella  Absent  DUS ISO 21567  
Vibrio  Absent  US ISO/TS 21872 -1 
 
6 Heavy metal contaminants  
Metal contaminants if present shall conform to the following limits.   
 
Table 2— Heavy metal contaminant limits for compo und microbial fertilizers  
Heavy metal   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  
 
7 Sampling  
 
7.1 Sampling for laboratory 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 th e production documents containing the number of bags per batch number 
and bag number.   
4 © UNBS 2018  – All rights reserved  
  
(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 mi xed. 
 
(4) Submit five kilograms (5 kg) of the composite sample to the laboratory.  
 
(5) Information relative 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 sampl es analyzed do not conform to the standards, the inspecting 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:  
 
(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 surface and mix thoroughly. Reduce sample to a quantity sufficient for 
analysis by quartering. Mi x 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.  DUS 2081: 2018  
© UNBS 2018  – All rights reserved  5 
 8 Packaging and storage  
8.1 The compound microbial fertiliser 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 Labelli ng 
9.1 Each container of the Compound microbial fertiliser shall bear a label in indelible marking in accordance 
with US ISO 7409, and with the following particulars:  
 
a) Product name as “ microbial compound  fertilizer  
b) Nutrient content(NKP)  
c) Carbon/Nitrogen rat io 
d) Organic matter content  
e) Moisture content  
f) Batch number  
g) Percentage foreign matter (gravel, plastic etc.)  
h) Name and physical address of the manufacturer/packer/importer  
i) Date of manufacture  
j) Best before date  
k) Instructions for use  
l) Precautions /warnings  
m) Country o f origin  
n) net content  
o) registration number  
p) form of product  
q) the name of strains used.  
9.2 Where the fertilizer is distributed in bulk, the labelling information shall accompany the delivery notice to 
the purchaser.   
6 © UNBS 2018  – All rights reserved  
 Annex  A 
(normative)  
 
Determination of Number  of active microbes  
Sample Requirements and Specimen Preparation  
Sample Requirements  
Information Record of Samples  
Number samples to be inspected with unique marks. Record the name, source, appearance, quantity, 
manufacturing date, shelf -life, name of stra in (Latin scientific name), sampler (sample escort) and date of 
sampling (sample delivery), executive standard, inspection method, preservation condition, transfer, handling, 
confidentiality and other information. The information should be recorded complet ely and truly.  
Sample Management  
Samples should be preserved by refrigeration or under normal temperature in accordance with product 
preservation requirements; avoid mix, contamination, deterioration, loss or damage during the preservation, 
preparation, sa mple separation and transfer. Samples under factory inspection should be preserved at least 
until the inspection results are confirmed; Supervision of random sample inspection should be implemented in 
accordance with the relevant provisions; in the event t hat clients have no objection to inspection reports, 
arbitral inspection samples and other entrusted inspection samples should be preserved at least one month 
after the inspection reports are issued or be handled in accordance with relevant agreements. Ins pected 
samples or those whose shelf -life expires should be recorded for clearance and be handled in accordance 
with requirements . 
Specimen Preparation  
A specimen should be divided from a sample mixed evenly. Specimen preparation for inspection of number of  
functional microorganism, percentage of contaminated microorganism, fecal coliforms and other relevant 
microorganism parameters should be executed in accordance with requirements of the sterile operation . 
Test Method  
Number of Functional Microorganism  
General Provisions 。 
Select Plate Count Method or Most Probable Number (MPN) Method in accordance with species and 
properties of functional microorganism in a sample. Plate Count Method involves five operating steps: 
preparation of medium plates, serial diluti on, sample adding and cultivation, colony recognition and colony 
count. Most Probable Number (MPN) Method adopts 5 -tube Method.  
Instruments and Equipment  
Besides instruments and equipment used for normal sterilization and cultivation in a microbiological laboratory, 
other instruments and equipment are as follows.  
Clean bench or clean room: cleanliness class of the clean room shall be 1000~100.  DUS 2081: 2018  
© UNBS 2018  – All rights reserved  7 
 Constant temperature incubator: the temperature resolution should not be lower than 0.5°C and the 
temperature fluc tuation is ±1°C.  
Oscillator (shaker). 。 
Electronic balance: with a sensitive quality of 0.001 g.  
PH meter. 。 
Microscope.  
Graduated pipettes: 0.5 mL graduated pipette (with graduation of 0.01 mL), 5 mL graduated pipette (with 
graduation of 0.1 mL) and 10 mL g raduated pipette (with graduation of 0.1 mL), etc.,  
Conical flasks: with volume of 500 mL and 150 mL.  
Culture dish: Ф9 cm.  
Operating Steps  
Preparation of medium plates  
Select a suitable medium in accordance with species of functional microorganism. Keep th e temperature of 
the medium prepared and sterilized (or degermed) in 45°C 〜 50°C and pour the medium into an aseptic 
culture dish under the aseptic condition, and the thickness should range among 3mm~5mm; lay it horizontally 
and then prepare it into a mediu m plate after its solidification. The plate for inspection should be free of 
contamination and cracks, and be flat and free of visible condensate water . 
Serial dilution  
Take and weight 10 g’ (accurate to 0.01 g) solid specimen and add it to a 500 mL conica l flask which has a 
stopper (tampon or silica gel stopper) and is filled with glass beads and 100 mL sterile water to stand for 
20min; take 10.0 mL liquid specimen and add it to a 500 mL conical flask which has a stopper and is filled with 
glass beads and 90 mL sterile water. After the oscillator fully oscillates for 30 min with a speed of 200 r/min, 
the preparation of basic bacterial suspension is done. Use a 5 mL or 10 mL sterile graduated pipette to draw 5 
mL bacterial suspension and add it into a 150 mL  conical flask which has a stopper and is filled with 45 mL 
sterile water. Shake it fully to obtain bacterial suspension of 1:1×10 1; then carry out serial dilutions at the ratio 
of 1:10 to successively obtain bacterial suspension with dilution degrees of 1 :1×10 2, 1:1×10 3, 1:1×10 4…  In 
the process of serial dilutions, different sterile graduated pipettes shall be used for different dilution degrees . 
Sample adding and cultivation  
Draw 0.10 mL bacterial suspension accurately and add it to a medium plate, and u se a sterile cloth bar to 
spread it evenly, and then invert it for culture under suitable conditions. Select different bacterial suspension of 
at least 3 continuous suitable dilution degrees, and each dilution degree should be repeated for at least 3 
times , and different sterile cloth bars shall be used for different dilution degrees. Meanwhile, sterile water is 
used as a blank control.  
Colony recognition  
After the cultivation, observe morphological features of the colony on the plate to identify the existi ng colony 
type; select various typical colonies for smear and dyeing, and observe the morphology of these colonies 
under the microscope, and compare and confirm the morphology in accordance with colonies, thalli and other 
features of functional microorgani sm. In case the functional microorganism cannot be identified, identification 
methods used in the biochemical test NY/T 1736 or NY/T 2066 shall be adopted to identify  the functional 
microorganism. When there are colonies on a plate for a blank control, the  testing result is invalid.   
8 © UNBS 2018  – All rights reserved  
 Colony count  
 Select a plate with a dilution degree within the count range of colonies, and separately count the number of 
functional microorganism’s colonies and calculate the average number of colonies under each dilution degr ee. 
In case the average number of colonies under two dilution degrees is within the count range, make a decision 
in accordance with the specific value of the total number of colonies under two dilution degrees. In case the 
specific value is smaller than or  equal to 2, the average number of colonies under two dilution degrees should 
be calculated; in case the specific value is bigger than 2, the average number of colonies under the lower 
dilution degree should be calculated. The standard deviation between nu mbers of colonies on plates with the 
same dilution degree should be calculated in accordance with Formula (1) and conform to provisions of Table 
1. 
 (1) 
Where:  
δn-1 — standard deviation, unit: Nrs. per dish (Nrs./dish); ； 
xi — number of colonies on plates with same dilution degree, unit: Nrs. per dish (Nrs./dish);  
x — average number of colonies on plates with same dilution degree, unit: Nrs. per dish (Nrs./dish);  
n — repeated times.  DUS 2081: 2018  
© UNBS 2018  – All rights reserved  9 
 Annex  B 
(normative)  
 
Determination of mortality of ascarid egg in fertiliz ers 
B.1 Principle  
Mix the alkaline solution thoroughly with the fertilizer sample to separate the ascarid eggs; use a solution 
having a higher density than the ascarid eggs as a floating fluid so that the ascarid eggs are floated on the 
surface of the solu tion to be collected and tested . 
B.2 Instruments and Equipment  
Reciprocal shaker; balance; centrifuge; wire ring (about ϕ1.0cm); Galtman funnel; microporous collodion filter 
membrane ( ϕ35mm; aperture 0.65μm ~ 0.80μm); suction flask; vacuum pump; microscope ; constant 
temperature incubator and other instruments and items commonly used in the laboratory.  
B3 Reagent  
B.3.1  50.0g/L Sodium hydroxide solution;  
B.3.2  Saturated sodium nitrite solution (density 1.38 ~ 1.40);  
B.3.3  500mL/L Glycerite;  
B.3.4  20mL ~ 30mL/ L Formaldehyde solution or formal saline.  
B.4 Sample Treatment  
B.4.1  Weigh and take a sample of 5.0g ~ 10.0g (the sample of larger particles should be ground first) and 
place it in a centrifug e tube with a capacity of 50Ml.  
B.4.2 Inject 25mL ~ 30mL of sodi um hydroxide solution followed by adding about 10 glass beads; plug the 
tube orifice tightly with a rubber plug; place the tube on the shaker for standing for 30min and then shake the 
tube with the shaker for 10min ~ 15min at a frequency of 200 r/min 〜300 r/min.  
B.4.2 When the shaking is done, remove the rubber plug on the centrifuge tube; homogenize fully the 
sample in the centrifuge tube with a glass rod; plug the tube orifice tightly with the rubber plug once again for 
standing for 15min ~ 30min an d then shake the tube for 10min~15min.  
B.5 Centrifugation  
B.5.1  Remove the centrifuge tube from the shaker and unplug the rubber plug; pipette the distilled water 
with a dropper to wash the sample attached to the rubber plug and the inner wall of the tube orifice into the 
tube; centrifuge it at 2 000 r/min ~ 2 500 r/min for 3 min ~ 5 min; discard the supernatant. Then add 
appropriate amount of distilled water and stir the precipitate with the glass rod.  
B.5.2  Repeat washing three times as above.   
10 © UNBS 2018  – All rights reserved  
 B.6 Centri fugal Floating  
B.6.1 Add a small amount of saturated sodium nitrate solution to the centrifuge tube; stir the precipitate into 
a paste with the glass rod, then slowly add saturated sodium nitrate solution while stirring until the solution is 
at about 1 cm away from the tube orifice.  
B.6.2 Rinse the glass rod with saturated sodium nitrate solution; incorporate the washing liquid into the 
centrifuge tube and centrifuge it at 2000 r/min ~ 2500 r/min for 3 min to 5 min.  
B.6.3 Move the liquid film of the surfac e layer of centrifuge tube constantly to a beaker containing half a cup 
of distilled water with the wire ring.  
B.6.4 Repeat this step for about 30 times before adding an appropriate amount of saturated sodium nitrate 
solution into the centrifuge tube.  
B.6.5 Then repeat the process of stirring, centrifugation and move of the liquid film for 3 to 4 times until no 
ascarid egg is observed on the liquid film smear under low -magnification microscope.  
B.7 Suction Filter and Microscopic Examination  
B.7.1 Mix the suspension into the beaker and apply suction filtration to it by a Galtman funnel covered with 
microporous collodion filter membrane. If the turbidity of mixed suspension is large, the filter membrane may 
be replaced.  
B.7.2 After the suction filtration, us e elbow tweezers to remove the filter membrane carefully from the 
funnel's filtering stage and place it onto a piece of glass slide; drop two or three drops of glycerite on the glass 
slide;  
B.7.3  Observe the whole filter membrane under low magnification m icroscope and count the ascarid eggs. 
When ascarid eggs are observed, the filter membrane containing ascarid eggs shall be cultured.  
B.8 Culture  
B.8.1  Lay a layer of absorbent cotton having the thickness of approximately 1 cm on the bottom of the Petri 
dish and place on that absorbent cotton a plain filter paper with a diameter that matches the Petri dish. In 
order to prevent mold and protozoan reproduction, formaldehyde solution or formal saline can be added 
(preferably the soaked filter paper and absorbe nt cotton).  
B.8.2  Lay the filter membrane containing ascarid eggs on the filter paper. Then the petri dish shall be 
capped and placed in the constant temperature incubator to be cultured at 28°C ~ 30°C. During the culturing, 
drop distilled water or formald ehyde solution often, so that the filter membrane can be kept wet.  
B.9 Microscopic Examination  
B.9.1 After culturing for 10 to 15 days, remove the filter membrane from the petri dish and place it on a 
glass slide. Add the glycerite solution dropwise to mak e it transparent. Look for the ascarid eggs under a low 
magnification microscope and then identify the viability of eggs under high magnification according to the 
morphology, and count accordingly.  
B.9.2 In the microscopic examination, if the brightness w ithin the field of view or the transparency of the 
membrane is insufficient, a drop of distilled water may be dropped onto the glass slide. Scrape a little bit of 
filter residue containing the eggs from the filter membrane with a cover glass and mix it wel l with water; apply 
the cover glass for microscopic examination . DUS 2081: 2018  
© UNBS 2018  – All rights reserved  11 
 B10 Judgment
  
Eggs containing larva are considered to be live eggs while eggs unhatched or unicellular are called death 
eggs.  
B11 Result Calculation  
Mortality of ascarid  egg (K) = 
12 1 ) 100(
NNN  
Where:  
K—Mortality of ascarid egg;  
N1—Total number of eggs for microscopic examination;  
N2—Number of live eggs for microscopic examination after culturing.  
 
Annex C  
(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 dichromate is titrated with ferr ous 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 and the value 
obtained i s 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 tra nsfer 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 K 2Cr2O7)=0.8mol/L 。 
Potassium dichromate solution: c(1/6 K 2Cr2O7)=0.8mol/L.   
12 © UNBS 2018  – All rights reserved  
 Weigh out 39.23g potassium dichromate (an alytically pure) 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 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.  
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 150mL 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 calculat ed by equation (1) based on the consumption 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 ind icator 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 p lace 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 into a 250mL triangular flask, add water to about 100mL, and add 
2~3 d rops 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 used in the blank test, the sample weight shall be reduced and re -
determined.  
B.1.6  Expression of Analysis Results  DUS 2081: 2018  
© UNBS 2018  – All rights reserved  13 
 The content of organic matter is expressed as the mass fraction of fertilizer and is calculated by equation (2) 
below:  
 
Where:  
 
c——Molar concentration of ferrous sulfate standard solution, in mol/L;  
 
V0——Volume of ferrous sulfate standard solution consumed in the bla nk 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 converting the organic carbon to the organic matter;  
1.5——Oxidation co rrection factor;  
m——Mass of air -dried sample, in g;  
X0——Moisture percentage of air -dried sample;  
D——Taking multiple, constant volume/taking volume, 250/50.  
  
14 © UNBS 2018  – All rights reserved  
 Bibliography  
[1] Agricultural Industry Standard of the People’s  Republic of China  — Compound microb ial fertilizers   
[2] Uganda Standard — Specification for Biofertilizer   
—DUS 2081: 2018  
© UNBS 2018  – All rights reserved  15 
 Certification marking  
Products that conform to Uganda standards may be marked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below.  
The use o f 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 wit h 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 
certif ication mark scheme of the Uganda National Bureau of Standards. UNBS marked products are 
continually checked by UNBS 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 2081: 2018    
 
ICS 65.080  
Price based o n nn pages  
© UNBS 2018 – All rights reserved