ISO 18644:2016

INTERNATIONAL ISO
STANDARD 18644
First edition
2016-04-15
Fertilizers and soil conditioners —
Controlled-release fertilizer —
General requirements
Matières fertilisantes — Engrais à libération contrôlée — Exigences
générales
Reference number
ISO 18644:2016(E)
©
ISO 2016

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ISO 18644:2016(E)

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ISO 18644:2016(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Classification . 2
5 Requirements . 2
6 Testing method . 3
7 Sampling and preparation of test sample . 4
8 Marking and labelling . 5
9 Package, transport, and storage . 5
Bibliography . 6
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ISO 18644:2016(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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electrotechnical standardization.
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The committee responsible for this document is ISO/TC 134, Fertilizers and soil conditioners.
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INTERNATIONAL STANDARD ISO 18644:2016(E)
Fertilizers and soil conditioners — Controlled-release
fertilizer — General requirements
1 Scope
This International Standard specifies the requirements for testing methods, sampling and preparation
of test sample, marking and labelling, as well as package, transport, and storage of controlled-release
fertilizer.
This International Standard is applicable to controlled-release products having one or more primary
fertilizer nutrient (nitrogen and/or phosphorous and/or potassium) in a controlled-release form. They
can be made by bulk blending (BB) fertilizers or by special processes.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 5315, Fertilizers — Determination of total nitrogen content — Titrimetric method after distillation
ISO 6598, Fertilizers — Determination of phosphorus content — Quinoline phosphomolybdate
gravimetric method
ISO 7409, Fertilizers — Marking — Presentation and declarations
ISO 7410, Fertilizers and soil conditioners — Final samples — Practical arrangements
ISO 7742:1988, Solid fertilizers — Reduction of samples
ISO 8397, Solid fertilizers and soil conditioners — Test sieving
ISO 8633, Solid fertilizers — Simple sampling method for small lots
ISO 17319, Fertilizers and soil conditioners — Determination of water-soluble potassium content —
Potassium tetraphenylborate gravimetric method
EN 13266, Slow-release fertilizers — Determination of the release of the nutrients — Method for coated
fertilizers
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
controlled-release fertilizer
fertilizer in which nutrient release is controlled, meeting the stated release rate of nutrient and the
stated release time at a specified temperature
Note 1 to entry: Typical examples are coated fertilizers.
[SOURCE: ISO 8157:2015, 2.1.12, modified]
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ISO 18644:2016(E)

3.2
controlled-release nutrient
one or more of the primary nutrient/s, nitrogen and/or phosphorus and/or potassium, in controlled-
release fertilizers with controlled-release characteristics
Note 1 to entry: In quantitative denotation, controlled-release nutrient does not include the parts of nutrients
without controlled-release characteristics. For example, if a 15-15-15 compound fertilizer only contains
controlled-release nitrogen, and on a mass fraction basis only 10 % of the total mass is controlled-release
nitrogen, then the term controlled-release nutrient only applies to the 10 % nitrogen.
3.3
initial release rate of nutrient
ratio of the fraction released within a 24 h time period at 25 °C (or such temperature specified by the
manufacturer) in static water, divided by the total controlled release fraction
Note 1 to entry: Sometimes there is a portion of the nutrient in the production of controlled-release fertilizer that
does not exhibit controlled-release characteristics, and as such is released ahead of time.
Note 2 to entry: The initial release rates of nutrients of multiple nutrient elements in controlled-release fertilizers
shall be denoted with the total nitrogen release rates; if no nitrogen is contained, the initial release rates of
nutrient shall be denoted as the release rates of phosphorus and/or potassium.
3.4
cumulative release mass fraction of nutrient
mass ratio of the cumulative released nutrient during a given period to the total of the nutrients,
denoted with the mass ratio of the cumulative released nutrients during several consecutive periods as
a whole, under condi
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