EN 15957:2011

Overview

EN 15957:2011 is a European Standard developed by CEN that specifies a precise method for the extraction of phosphorus soluble in neutral ammonium citrate from fertilizers. This standardized approach is crucial for ensuring consistent, reliable measurement of phosphorus content in fertilizers, particularly those regulated under the European Regulation (EC) 2003/2003, Annex I. EN 15957:2011 replaces the earlier technical specification CEN/TS 15957:2009 and serves as a mandatory reference for fertilizer quality control and regulatory compliance across EU member states.

The method outlined in EN 15957:2011 involves using a neutral ammonium citrate solution at pH 7 for extracting phosphorus at a controlled temperature of 65 °C. This procedure allows for assessing the phosphorus content that is readily soluble, which is an important indicator of fertilizer effectiveness and environmental impact.

Key Topics

• Phosphorus Extraction Method
  Applies a neutral ammonium citrate solution to extract phosphorus soluble under neutral pH conditions. The extraction takes place at 65 °C over a one-hour period while stirring to ensure uniform suspension.

• Sample Preparation
  Although sampling is outside the method's direct scope, it recommends adherence to EN 1482-1 and EN 1482-2 for proper sampling and sample preparation, including grinding to achieve sample homogeneity.

• Reagents and Apparatus
  Essential reagents include distilled or demineralized water and a precise neutral ammonium citrate solution prepared by carefully neutralizing citric acid with ammonium hydroxide. The required apparatus comprises Erlenmeyer flasks, pH meters, a thermostatically controlled water bath with stirring capability, and phosphate-free filters.

• Test Procedure
  The test involves weighing a specific portion of fertilizer into an Erlenmeyer flask containing preheated ammonium citrate, shaking and stirring while maintaining the temperature, followed by cooling, dilution, and filtration to obtain the clear extract for analysis.

• Reporting Requirements
  The test report must include sample identification, applied method reference, test results, dates of sampling and analysis, repeatability information, and any deviations or incidents impacting results.

Applications

EN 15957:2011 is pivotal in various practical scenarios, including:

• Quality Control in Fertilizer Production
  Manufacturers use this method to verify the phosphorus solubility content in accordance with EU regulatory requirements, guaranteeing product consistency and effectiveness.

• Regulatory Compliance
  Ensures fertilizers meet the solubility criteria outlined in Regulation (EC) 2003/2003, facilitating lawful market access and consumer safety assurance.

• Agricultural Research and Soil Fertility Studies
  Researchers rely on this standardized extraction technique to study nutrient availability from fertilizers and its effect on crop yields and soil health.

• Environmental Monitoring
  Accurate measurement of soluble phosphorus in fertilizers helps mitigate nutrient runoff risks, supporting sustainable farming practices.

Related Standards

• EN 1482-1 & EN 1482-2 – Provide essential guidelines for sampling and sample preparation of fertilizers, complementing EN 15957:2011 for accurate laboratory results.

• Regulation (EC) No 2003/2003 – European legislation governing fertilizer products, specifying phosphorus solubility requirements that EN 15957 helps to assess.

• EN 12944-1 & EN 12944-2 – Define vocabulary and terminology relating to fertilizers, ensuring uniformity in documentation and communication.

Summary

EN 15957:2011 establishes a reliable, repeatable method for extracting phosphorus soluble in neutral ammonium citrate from fertilizers, fostering harmonized quality assessment and compliance within the European fertilizer industry. By adhering to this standard, laboratories and manufacturers can ensure accurate phosphorus analysis, facilitating regulatory adherence and promoting sustainable fertilizer use.