What is ISO 20978 about?
ISO 20978 is a standard that covers specifications on titrimetric methods for the determination of neutralizing value in liming materials that enables increased nutrient availability and improvement in soil structure. ISO 20978 specifies two methods for the determination of the neutralizing value (NV) of liming materials.
In ISO 20978, method A is applicable to all liming materials except silicate liming materials. Examples of hard liming materials are limestone and dolomite. Examples of soft liming materials are chalk, marl and burnt lime.
In ISO 20978, method B is applicable to all liming materials. Neither method correctly takes into account the potential neutralizing value of material containing more than 3 % P2O5. For a more accurate agronomic assessment of products containing more than 3 % P2O5, EN 14984 is used to determine the liming efficiency.
Note 1: The methods described in ISO 6598 and ISO 7497 can be used for the determination of P2O5 content. Further information on P analyses is given in References [5] and [6].
Note 2: Carbonate consumes H+ and removes acidity in solution with subsequent dissociation to H2O and CO2. Forms of orthophosphate can consume H+ but are not dissociated to molecular forms that remove acidity. The acidity is back titrated with alkali causing an underestimation of NV.
Who is ISO 20978 for?
ISO 20978 on neutralizing value in liming material is applicable to:
- Manufacturers of agricultural lime
- Testing houses and labs for liming materials
- Soil assessment services
Why should you use ISO 20978?
Liming is the process of applying calcium- and magnesium-rich minerals, such as marl, chalk, limestone, burnt lime, or hydrated lime, to soil. This frequently stimulates plant development and increases soil microbial activity, maintain pH levels and improvement in soil structure.
ISO 20978 provides you information on principle, reagents, apparatus, sampling, procedure, calculation, expression of results and precision which enables you to effectively determine the neutralizing value of liming materials.
ISO 20978 provides you information on two methods for determining the neutralizing value which gives you the flexibility to pick the appropriate method for your specific applications.
The guidance in ISO 20978 enables you to accurately determine the neutralizing value of liming materials to assess the ability of the product to deliver potential neutralization capacity in soils to maintain pH values.
