ISO 19822:2018 肥料と土壌改良剤—肥料材料中の腐植物質と疎水性のフルボ酸濃度の測定 | ページ 2

Foreword

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This document was prepared by Technical Committee ISO/TC 134, Fertilizers and soil conditioners.

Introduction

Humic substances are present in all ecosystems: oceans, rivers, lakes, and top soils. Quantifying the amount of humic material present in these systems is essential for academic research and commercial applications, specifically agricultural soil and plant management.

The increased use of humic substances in agriculture has generated intense interest among producers, consumers, and regulators for a reliable method for quantification of the active ingredients in raw humic ores and commercial fertilizer products; specifically humic and fulvic acids. As both commercial trade and regulation of humic products are based on percentage (%) of the humic and fulvic acids in commercial humic products, use of % units instead of SI units is warranted, therefore incorporated into this standard.

This document establishes a method for the determination of humic acids (HA) and acidic hydrophobic fulvic acids (HFA). The method is based on an existing preparative procedure use by the International Humic Substances Society (IHSS) for extracting high purity HA and HFA from soil samples^[1], which is a modified form of the “classical” technique described in detail by Stevenson^[2]. The “classical” methods and the IHSS method were developed as preparative methods for the fractionation of soil organic matter; they were not intended to be used as quantitative analytical methods. The classical method of extracting humic acids and fulvic acids from soil humus utilize a “strong base” to extract the alkaline soluble materials, and then the alkaline extract solution is acidified to flocculate the humic acids, which appear to precipitate out of solution. The remaining substances in solution after alkaline and acid treatment were called fulvic acids.

This method modifies the “classical” technique in a number of ways:

• it determines the quantity of humic substances on an “ash free” basis (mineral salts excluded);
• the alkali extraction is done under anoxic conditions to reduce oxidation of the analytical sample during extraction;
• it defines the materials that are soluble in both alkali and acid as the Fulvic Fraction;
• it can differentiate products containing certain non-humic materials that some manufactures claim to contain humic substances;
• it further defines HFA as materials of low sulfur content^[3] that bind to a hydrophobic resin at pH 1^[4][5][6], instead the classical, and perhaps more common definition, for fulvic acids as materials that are defined as soluble in both acid and alkali solution. This stricter definition is necessary to distinguish HFA from mineral salts, polysaccharides, amino sugars, amino acids, proteins, acids, and carbohydrates that are extracted along with humic substances when using the “classical” method^[1][4].

See Annex B for information on ISO/CD 19822 interlaboratory study.

1 Scope

This document specifies the procedure for the analysis of humic acids and hydrophobic fulvic acids which is applicable to dry and liquid materials used as ingredients in commercial fertilizers, soil amendments, and geological deposits.

2 Normative References

There are no normative references in this document.

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

Bibliography