Fertilizer

What exactly is fertilizer?

In addition to sufficient water, plants need nutrients (e.g., nitrogen, phosphate, potassium) and trace elements (e.g., copper and zinc) to develop and grow. Only then can they achieve high yields of good quality. Plants absorb nutrients and trace elements from the soil through their root system. The humus content of the soil plays a central role in this process. Humus is rich in plant nutrients and has a high water storage capacity. Only if the soil regains the nutrients that are removed from it when the plants are harvested can its fertility and agricultural yield potential be secured in the long term. It is therefore essential to supply the soil – and thus the plants growing on it – with sufficient fertilizer tailored to the nutrient requirements of the plants. Fertilizers are divided into organic and synthetic fertilizers, also known as mineral fertilizers. Organic fertilizers include animal excrement such as manure, farmyard manure, and slurry (farm manure). Green manure, mulch, organic residual fertilizers, and growing media such as composted organic waste, sewage sludge, growing media (peat), and fermentation residues are also organic fertilizers. Synthetic fertilizers, on the other hand, are produced by technically processing natural raw materials and are available as single or multiple nutrient fertilizers.

Environmental impact

If handled improperly, the storage and application of fertilizers can cause a whole range of serious environmental damage. The production of synthetic fertilizers is also very energy-intensive, which is associated with high resource consumption and greenhouse gas emissions. Nitrogen and phosphorus in particular can have a negative impact on soil fertility and water quality if these substances are released into the environment in excessive amounts. Air quality can be impaired by ammonia emissions generated during manure management (from livestock housing and during the storage and application of manure) and during the application of urea fertilizers in particular. Nitrous oxide emissions released from fertilized soils contribute to global warming, as this is a very powerful greenhouse gas.

Heavy metals in fertilizer

In addition to the desired trace nutrients (such as copper, zinc, and iron), fertilizers also contain heavy metals that are not needed by plants. These include, for example, lead, cadmium, nickel, mercury, arsenic, and uranium in varying amounts. With intensive fertilization, these can accumulate in the soil and enter the food chain and groundwater via plants. Mineral phosphorus fertilizers made from sedimentary raw phosphates, which naturally have high heavy metal contents (especially cadmium and uranium), play a significant role in this process.
Heavy metals enter sewage sludge through corrosion of water pipes, from the metalworking and processing industries, and from medications, among other sources. The accumulation of heavy metals in farm manure (especially zinc and copper, and in pig manure also arsenic) can be caused, for example, by additives used in animal feed. All heavy metals are toxic in high concentrations, but some are also essential trace elements and necessary for important metabolic processes in plants, animals, and humans (e.g., copper, iron, and manganese).
Heavy metals that are absorbed by plants and animals and thus enter the food chain are relevant to human health. The “Heavy Metal Transfer Soil/Plant” working group of the Länderarbeitsgemeinschaft Boden (LABO) identified the elements arsenic, lead, cadmium, mercury, and thallium as “primarily relevant” to food plant quality. In feed crops, it is mainly nickel and copper that can accumulate in animal-based foods.
Zinc and copper are not only dangerous to humans, but also toxic to some soil microorganisms. This can impair soil fertility in the long term.

Fertilizer legislation

The Fertilizer Act (DüngG) and the associated ordinances form the legal basis for the manufacture, marketing, and use of fertilizers, soil additives, plant additives, and growing media. The Fertilizer Ordinance (DüMV) defines the requirements for placing fertilizers on the market, compliance with which is monitored by the official fertilizer market control authority (DVK). According to the Fertilizer Act, fertilizers may only be used in accordance with good professional practice and must be tailored to the nutrient requirements of the plant and the soil in terms of type, quantity, and timing. When fertilizing, the nutrients and organic matter available in the soil as well as the location and cultivation conditions must also be taken into account. The relevant application criteria are defined and specified in the Ordinance on Good Professional Practice in Fertilization (Fertilizer Ordinance, DüV). These include, for example, regulations for determining fertilizer requirements, application times, distance regulations from surface waters, application limits, and specifications for reducing atmospheric ammonia losses. The Fertilizer Ordinance is the central element of the German action program for implementing t ere largely insufficient and the nitrate pollution of groundwater near the surface remains almost unchanged (Nitrate Report 2024). Due to the alleged inadequate implementation of the Nitrates Directive, the EU Commission filed a lawsuit with the European Court of Justice (ECJ) in October 2016. In June 2018, the European Court of Justice (ECJ) ruled against Germany in infringement proceedings for failing to implement the Nitrates Directive. In its ruling, the ECJ agreed with the Commission on all points of complaint. According to the ruling, Germany violated the Nitrates Directive by failing to take additional measures to revise the inadequate German action program (in the form of the Fertilizer Ordinance). The ECJ's ruling is comprehensible and well-founded in all respects. The significant shortcomings of the old action program were remedied by the fertilizer legislation revised in 2017 and again in 2020, which is why the EU Commission closed the proceedings in June 2023. It underwent extensive revision in a process lasting many years, and the current version has been in force since May 1, 2020. The revision was long overdue, as the previous requirements were largely insufficient and the nitrate pollution of groundwater near the surface remains almost unchanged (Nitrate Report 2024). Due to the alleged inadequate implementation of the Nitrates Directive, the EU Commission filed a lawsuit with the European Court of Justice (ECJ) in October 2016. In June 2018, the European Court of Justice (ECJ) ruled against Germany in infringement proceedings for failing to implement the Nitrates Directive. In its ruling, the ECJ agreed with the Commission on all points of complaint. According to the ruling, Germany violated the Nitrates Directive by failing to take additional measures to revise the inadequate German action program (in the form of the Fertilizer Ordinance). The ECJ's ruling is comprehensible and well-founded in all respects. The significant shortcomings of the old action program were remedied by the fertilizer legislation revised in 2017 and again in 2020, which is why the EU Commission closed the proceedings in June 2023.

The regulation on the marketing and transport of farm manure regulates the placing on the market, transport, and transfer of farm manure and covers the nutrient flows that occur in trade.
Effective control of agricultural fertilization is necessary to prevent heavy metal contamination of the soil and hazards to humans and the environment. In Germany, heavy metal inputs are restricted by regulations under fertilizer law (DüMV) and waste law (BioAbfV, AbfKlärV). In addition, soil protection legislation (BBodSchV) and food and feed law (LFGB) contain specifications on limit values for heavy metals and pollutants. However, there are some significant differences in regulation between these areas of law. These relate, for example, to the regulated pollutants themselves, their contents and loads, the limit values to be complied with, and the weighting of protection goals (human and animal health, natural balance, environmental media). In addition, there are some discrepancies with applicable EU law.
The Federal Ministry of Food and Agriculture (BMEL) has therefore commissioned the Scientific Advisory Board for Fertilization Issues at the BMEL to develop a proposal on how to achieve effective, easily enforceable regulations for pollutants in fertilizer law that can be transferred to future EU law if necessary. The draft proposal offers a comprehensive approach to the uniform assessment of pollutants in fertilizers and to limiting the amounts of pollutants applied through fertilization. It has been available since February 2011 and can be downloaded from the BMEL website.
This draft proposal does not include a limit value for the heavy metal uranium. This heavy metal is currently not adequately addressed in environmental legislation. Research projects provide evidence of uranium entering soil, seepage water, and groundwater through phosphate fertilizers. On average over the last ten years, approximately 167 tons of uranium have been applied to arable land annually with phosphate fertilizers, which could lead to high drinking water treatment costs in the long term if it migrates into the groundwater.
The Soil Protection Commission at the Federal Environment Agency therefore recommends regulating the uranium content in phosphate fertilizers (as with cadmium) as follows: labeling from 20 milligrams of uranium per kilogram of phosphate, limit value 50 milligrams of uranium per kilogram of phosphate.