Organic Farming

Mineral fertilization to supply nutrients

A needs-based nutrient supply has a significant influence on the quality and yield of the harvested products. Learn more about fertilization in organic farming.

Requirements for organically produced food are high: it should not only taste and look good, but also be free of residues and rich in valuable ingredients. Consumers are attaching increasing importance to the method of production, with sustainability and harmony with nature at the forefront. The nutrient supply of the crops also plays a major role here, because the quality and yield of the harvested products are significantly influenced by plant nutrition.

Adequate supply of nutrients in organic farming

The goal of organic agriculture is to farm in a closed nutrient cycle. Organic fertilizers return many nutrients to the fields. With the sale of plant and animal agricultural products, however, this cycle is interrupted. The nutrients contained in the marketed harvested products are no longer available to the farm and must be replaced accordingly.


For some nutrients, the use of the farm's own organic fertilizers - depending on their composition - is not sufficient to completely cover the requirements. Experience shows that in practice, phosphorus and potassium in particular, but also magnesium and sulfur, are in short supply. This results in nutrient deficiencies.

Even if the annual deficit appears to be small, the deficiencies accumulate over the years and unbalance the soil fertility due to declining nutrient stocks - with consequences for yield, quality and the profitability of the farm.

Close nutrient gaps

Mineral fertilizers are also used in organic farming to close nutrient gaps. According to the regulations EU 2018/848 and EC No. 889/2008, mineral fertilizers can be applied if necessary to cover the nutrient requirements of the plants, therefore closing the nutrient cycle and ensuring the soil fertility of the site. The proven need must be reported to the inspection body or authority.

Mineral fertilizers based on largely natural raw materials are permitted. Examples are crude potash salts, sulfatic potassium fertilizers or magnesium sulfate, which are extracted from mines and processed into natural mineral fertilizers in a few gentle production steps.

Mineral fertilizers for organic farming:

  • Potassium: Crude potassium salt and potassium sulfate from natural deposits.
  • Magnesium: Natural kieserite (magnesium sulfate)
  • Phosphorus: Soft rock phosphates

Mineral nitrogen fertilizers are not permitted in organic farming.

Determine fertilizer requirement

The extent of mineral supplementary fertilization depends in particular on the farming method (arable farming with or without livestock) as well as the type of harvested products and their nutrient contents. In terms of nutrient removal, cropland and vegetable fields are often affected to a greater extent than grazed grassland.

Soil testing and nutrient comparisons (balances) can be used to verify the need for supplemental mineral fertilization. It is important to have the actual nutrient content of organic fertilizers analyzed, as this may differ from the published guideline values due to differences in feeding. The availability of nutrients must also be taken into account. For example, only 5-10% of the sulfur contained in manure is available in the respective growing year.


Mineral fertilization in organic farming

With the marketing of plant or animal products, the nutrient cycle is interrupted and this endangers the soil fertility of the site in the long term. Mineral fertilizers based on largely natural raw materials can also be used in organic farming to close these nutrient gaps. These include potash crude salts, potassium sulfate, and magnesium sulfate.