• Fertilizer quality is not only about nutrient content, but also about physical properties and contamination levels.
  • Precise analyses make it possible to confirm that products comply with standards and to detect even trace amounts of harmful elements.
  • Łukasiewicz – Institute of New Chemical Syntheses in Puławy conducts research, provides opinions on fertilizers, and develops methods for controlling their quality.

Today, the fertilizer market is one of the significant segments of the agricultural economy. Thanks to appropriately selected mixtures of macronutrients and micronutrients, agriculture can use soil resources efficiently and achieve high yields. However, before a given fertilizer product can be sold, it must undergo rigorous quality control. In addition, monitoring products already on the market is essential to protect farmers from unfair practices and the environment from potential contamination. In practice, this means carrying out hundreds of analyses—from basic physicochemical tests to advanced determinations of trace elements. And this is where the challenge begins, because fertilizers are among the most difficult matrix groups to analyze, and laboratories performing control tests face problems that are not immediately apparent.

Why is fertilizer analysis so demanding?

Few people outside the industry realize how complex modern fertilizer products are. They contain, among other things, mixtures of mineral salts, organic ingredients, fillers, micronutrients, inhibitors, and sometimes natural mineral contaminants. Each of these components can affect the analysis. The main challenges laboratories face are: the matrix effect, which can interfere with spectroscopic measurements due to the high salt content (e.g. phosphates, chlorides, nitrates), while the organic composition can disrupt the mineralization process; high sample heterogeneity — as a result, NPK fertilizer granules, micronutrient mixtures and organic fertilizers require very precise sampling, since even slight heterogeneity can change the result; the presence of elements in forms that are difficult to dissolve, since not all components can be easily extracted — this applies especially to phosphorus, calcium and micronutrients bound in mineral structures; and the need to measure very low concentrations of contaminants. In practice, this means that analyses must be performed with accuracy reaching parts per billion (ppb), which requires the use of top-class equipment and rigorously controlled analytical procedures. Advanced instrumental techniques make it possible to detect even trace amounts of elements such as cadmium, lead and arsenic, which is crucial for ensuring environmental and health safety. Therefore, fertilizer analysis is not routine work, but precise analytical work in which every stage — from sampling to interpreting the results — matters.

Although laboratories today have plasma spectrometers, X-ray spectrometers and advanced spectral analysers at their disposal, classical methods remain an integral part of quality control. Although they may seem “old-fashioned,” they continue to form the basis of many reference procedures. Titration (volumetry) is used to determine, among other things, nitrogen in ammonium and nitrate forms, alkaline hardness (Ca, Mg), and iron and manganese. These are highly accurate techniques, but they require time, experience and meticulousness. Colorimetric methods are still widely used to determine phosphorus in forms available to plants. The colour of the phosphorus-molybdenum complex is a delicate indicator, susceptible to interference, which makes the quality of reagents and sample preparation extremely important. Gravimetric methods commonly used in laboratories (e.g. determining total sulphur by precipitating barium sulphate) are characterised by high accuracy, but are unfortunately also time-consuming and require ideal laboratory conditions. Basic physicochemical analyses such as moisture measurement, particle size analysis and bulk density analysis are essential in practice and determine the functional quality of fertiliser—ease of application, durability and resistance to caking.

Spectroscopy as a modern tool for market surveillance and elemental analysis

Spectroscopic techniques complement classical methods, making it possible to perform analyses faster and with greater precision, and to determine multiple elements simultaneously using advanced analytical equipment.

  • ICP- OES – inductively coupled plasma optical emission spectrometry – enables the rapid determination of several dozen elements in a single analysis, including both macronutrients and micronutrients (P, K, Mg, Ca, Fe, Zn, Cu, Mn, B, Mo, Co, Ni and many others).
  • ICP- MS – inductively coupled plasma mass spectrometry – is indispensable for determining heavy metals, trace elements and undesirable mineral contaminants. Its distinguishing feature is excellent sensitivity, allowing even trace amounts of cadmium or lead, which are unwanted in fertiliser composition, to be detected.
  • XRF – X-ray fluorescence - a non-destructive technique, ideal for the rapid inspection of raw materials or granules, allowing the immediate assessment of the content of the main components without the need to dissolve the sample or digest it with acids.
  • FTIR and NIR – infrared spectroscopy - used to analyze, among other things, organic matter content, identify components in organo-mineral fertilizers, and detect contaminants and adulteration. These are rapid methods, often used for process control.

Pre-market inspection vs. inspection of products already on the market

Inspection before market authorization

For a fertilizer to receive a label and be sold, it must undergo a detailed analysis of the conformity of its declared composition with its actual composition, the level of contaminants, the solubility of nutrients, and physical parameters such as granulation and moisture content. This stage requires the use of a wide range of analytical methods.

Inspection of products already on the market

The most frequently detected analytical problems concern nutrient concentrations below the declared levels, the presence of non-compliant additives or fillers, contamination from raw materials, or changes in quality as a result of storage (e.g., caking or the decomposition of organic components). Accordingly, market surveillance serves a protective function—it prevents unfair practices by manufacturers and ensures environmental safety.

Advanced methods for fertilizer quality control

At Łukasiewicz - INS, advanced methods for quality control of fertilizer products are being developed, representing an important element in ensuring food security and environmental protection. Modern quality control is no longer limited to basic chemical composition analysis; it includes comprehensive physicochemical testing, assessment of functional properties, and monitoring of contaminants. Our Analytical Laboratory uses modern analytical techniques, such as inductively coupled plasma optical emission spectrometry (ICP-OES), ion chromatography (IC), and electrothermal atomic absorption spectrometry with graphite furnace atomization (ETAAS). These techniques enable precise determination of macro- and micronutrients, as well as trace amounts of heavy metals. This makes it possible not only to confirm that fertilizers comply with applicable standards, but also to optimize their composition for agronomic efficiency. An important area of the institute’s activity is also the testing of the physical properties of fertilizers, such as granulation, mechanical strength, and hygroscopicity. These parameters are crucial for transporting, storing, and applying fertilizers under field conditions. Increasing emphasis is being placed on controlling the content of organic contaminants and potentially harmful substances, in line with the principles of a circular economy and sustainable agriculture.

Fertilizer opinions and assessment of their safety

An important complement to the research activities of Łukasiewicz – Institute of New Chemical Syntheses is the process of issuing opinions on fertilizers, which is an important stage in bringing new products to market. The institute acts as an independent expert body, conducting a substantive assessment of the composition, properties, and declared functions of fertilizers and products supporting plant cultivation. The opinion process includes an analysis of technical documentation and test results and, where necessary, additional tests to verify the declared parameters. Particular attention is paid to the products’ compliance with applicable national and European regulations, as well as their safety for soil, plants, people, and the environment. The institute’s experts also assess the agronomic efficiency of fertilizers, making it possible to determine their actual practical value. This process is an importantand support both manufacturers improving their products and end users, who gain confidence in the quality of the products they use. By combining advanced equipment, expert competence, advisory activities, and cooperation with industry and agriculture, Łukasiewicz – INS in Puławy plays a key role in developing and implementing fertilizer quality standards, supporting the development of modern, effective, and safe fertilizer products.

PCA Accreditation – A Guarantee of Reliable Fertilizer Testing

The comprehensive quality control system at Łukasiewicz – INS is complemented by testing methods accredited by the Polish Centre for Accreditation (PCA). This accreditation formally confirms that laboratories are competent to perform specified tests in accordance with the international standard PN-EN ISO/IEC 17025. In practice, this means that the analytical procedures used at the institute are thoroughly validated—checked for precision, repeatability, and accuracy—which ensures that the results obtained are highly reliable. In accordance with the scope of accreditation of Analytical Laboratory No. 180, the Institute performs a wide range of tests for key fertilizer quality parameters. These include, among other things, the content of the primary nutrients—nitrogen, phosphorus, and potassium—their forms available to plants, as well as trace elements and potential contaminants such as cadmium, lead, or arsenic. These tests use both classical analytical methods and modern instrumental techniques, and the scope of accreditation is systematically expanded in response to changing legal requirements and the needs of the fertilizer market. However, the significance of PCA accreditation goes beyond product quality control. It is the foundation of trust in relations with industrial partners and certification bodies at home and abroad. Test results obtained by accredited laboratories are widely recognized in conformity assessment systems, enabling fertilizer manufacturers to effectively introduce their products to international markets. Thus, at Łukasiewicz – Institute of New Chemical Syntheses in Puławy, fertilizer quality is not only monitored, but the competitiveness of the fertilizer sector is also actively supported by providing reliable analytical facilities recognized worldwideytical.

Precision That Determines Fertilizer Quality

Fertilizer analysis is a precise science, not routine work, and testing the quality of fertilizer products combines chemical techniques, advanced spectroscopy, analysts’ expertise, and rigorous sampling and sample preparation procedures. It is an area where even seemingly minor errors can have major consequences for both agriculture and the environment. Consequently, fertilizer quality control remains one of the most demanding analytical tasks in modern applied chemistry.