ISO 18645:2016

Overview

ISO 18645:2016 - Fertilizers and soil conditioners - Water soluble fertilizer - General requirements - defines quality, testing, sampling, marking and packaging rules for water soluble fertilizers. It applies to products that are completely soluble in water and intended for fertigation, sprinkler irrigation, and foliar application (foliar feeding). The standard helps manufacturers, testing laboratories and regulators demonstrate product conformity and safe handling through specified test methods and labelling requirements.

Key topics and technical requirements

• Scope and applicability: Covers powders, prills and granules that are fully water‑soluble and used in irrigation and foliar feeding.
• Product appearance: Products must be free of foreign matter on visual inspection.
• Nutrient content requirements: Declared values for primary (N, P2O5, K2O), secondary and micronutrients must be verifiable. The standard lists minimum/marked values and references relevant regional rules (e.g., EC Regulation 2003/2003).
• Critical limits and characteristics:
  • Mass fraction of total primary nutrient (N + P2O5 + K2O) and declared primary nutrient minima (see standard for detailed thresholds).
  • Mass fraction of water‑insoluble matter ≤ 0.5% (test procedure described).
  • pH (10 g/100 mL water) between 2.0 and 9.0.
  • Biuret content limit ≤ 1.2% where applicable (urea‑based products).
  • Chloride limits and labelling rules - products containing chloride must be labelled “contains chloride”; local regulations may apply.
  • Heavy metals (As, Cd, Pb, Cr, Hg) and micronutrient contents are subject to specified test methods and regional limits.
• Test methods and references: Normative methods are referenced (e.g., ISO 5315 for nitrogen, ISO 6598 for phosphorus, ISO 17319 for potassium, ISO 17318 for heavy metals, ISO 18643 for biuret, and multiple EN standards for chelated micro‑nutrients and sulfates).
• Sampling and sample preparation: Sampling protocols for bagged and bulk products follow ISO 8633 and sample reduction procedures are specified.
• Marking, labelling, packaging, transport and storage: Requirements ensure accurate declarations and safe distribution.

Practical applications and users

• Fertilizer manufacturers use ISO 18645:2016 to design quality control procedures, labelling and shipping practices for water‑soluble products.
• Analytical laboratories apply the referenced test methods to verify declared nutrient contents and contaminants.
• Regulators and certification bodies rely on the standard for compliance assessment and market surveillance.
• Distributors, agronomists and growers benefit from consistent labelling and testable quality for products used in fertigation and foliar feeding.

Related standards

Relevant normative references include ISO 5315, ISO 6598, ISO 17319, ISO 17318, ISO 18643, and various EN methods for chelating agents and sulfate determination. Consult ISO 18645:2016 for the full list of referenced documents and detailed procedures.

Keywords: ISO 18645:2016, water soluble fertilizer, fertigation, foliar feeding, testing methods, sampling, labelling, pH, biuret, water insoluble matter, chelated micronutrients.