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Fertiliser requirement under the German DüV explained

What the fertiliser requirement calculation under section 4 DüV contains, when soil samples are needed, which deadlines apply to records and who is exempt.

PhytAI editorial teamPublished 5 min read

Key points

  • Before fertilising: calculate and record the fertiliser requirement for nitrogen and phosphate per field or management unit (sections 3, 4 and 10(1) DüV).
  • Nitrogen: requirement value from Annex 4 with additions and deductions, among others for the yield level, the Nmin content of the soil, humus supply, organic fertilisation in the previous year and preceding crops.
  • Phosphate: requirement based on expected removal; soil analysis for phosphate at least every six years per field of one hectare or more.
  • After fertilising: record each application within 14 days; farm-level annual summary by 31 March of the following year.
  • Retention: seven years after the end of the fertiliser year.

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Before significant amounts of nutrients are applied to a field, the German Fertiliser Ordinance (Düngeverordnung, DüV) requires a fertiliser requirement calculation (Düngebedarfsermittlung) for nitrogen and phosphate. It sets the upper limit for fertilisation and is the basis of every inspection. This article explains how the calculation is structured, which records belong to it and where farms often stumble.

Structure of the nitrogen calculation

For arable land and vegetables, section 4(1) DüV sets the nitrogen requirement as a site-specific upper limit. The calculation follows a fixed scheme:

  1. Nitrogen requirement value of the crop from Annex 4 (Table 2 for arable crops, Table 4 for vegetables) at a defined yield level.
  2. Addition or deduction for the yield level: based on the average yield of the last five years.
  3. Deduction of plant-available nitrogen in the soil (Nmin): by analysing representative samples or using reference values or calculation methods of the competent authority.
  4. Deduction for nitrogen supply from soil reserves, for example on soils with high humus content.
  5. Deduction for organic fertilisation in the previous year: 10 % of the total nitrogen applied with organic fertilisers in the previous year.
  6. Deduction for preceding and catch crops according to Annex 4, Table 7.

The result is the nitrogen requirement in kg N per hectare. It may be exceeded only in exceptional cases, for example if a higher requirement arises later; this must also be justified and recorded.

For grassland and multi-cut forage crops, section 4(2) DüV applies with separate tables in Annex 4, including nitrogen fixation by legumes.

Special case: vegetables

If vegetables follow vegetables, the Nmin content must be determined annually by analysis according to section 4(4) DüV. Reference values are then not sufficient.

Phosphate

The phosphate requirement is based on the crop's need at the expected yield, the nutrient contents in Annex 7 and the phosphate available in the soil. For this, section 4(4) DüV requires a representative soil analysis at least every six years for each field of one hectare or more, usually within the crop rotation. On soils with a high phosphate supply, phosphate fertilisation is limited.

What must be recorded

Before fertilising (section 10(1) DüV):

  • the calculated fertiliser requirement with the basis of the calculation
  • soil values and the methods used to determine them
  • reasons if the requirement is exceeded

After each application, within 14 days (section 10(2) DüV):

  • name and size of the field or management unit
  • type and quantity of the fertiliser
  • quantities of total nitrogen and phosphate applied, for organic fertilisers also the available nitrogen

The deadline was extended from two to 14 days on 1 January 2025, as the fertiliser authority of Lower Saxony reports.

By 31 March of the following year: the farm-level summary of fertiliser requirement and nutrient use described in Annex 5 of the DüV.

Who is exempt?

Section 10(3) DüV exempts, among others, areas with ornamental plants, Christmas tree plantations and nurseries. The record-keeping duty also does not apply to farms that meet all of the following conditions:

  • less than 15 hectares of agricultural land, excluding the exempt areas
  • at most 2 hectares of vegetables, hops, vines or strawberries
  • no more than 750 kg of nitrogen per farm per year from livestock manure
  • no intake of manure or digestate from outside

Check the exemption carefully: a single condition that is not met leads to the full duty.

Nitrate-polluted areas

In nitrate-polluted areas under section 13a DüV, additional requirements apply. The best known is the reduction of the nitrogen requirement by 20 % in the farm total for the fields in these areas, with exceptions for farms that manage in a particularly water-friendly way. The federal states designate which areas are affected.

Common mistakes

  • Calculation made after fertilising: the calculation must exist before the first application.
  • Yield level not documented: the average of the last five years must be traceable.
  • Organic fertilisation of the previous year forgotten: the 10 % deduction is often overlooked.
  • Old soil analysis: phosphate values older than six years no longer support the calculation.
  • Annual summary missing: the summary due by 31 March is often only prepared during an inspection.
  • No recalculation: if crop or yield expectation change, the calculation should be adjusted and justified.

Nutrient flow balance and nutrient comparison

The Nutrient Flow Balance Ordinance (StoffBilV) was repealed in 2025. The former nutrient comparison with a control value was already dropped with the 2020 DüV amendment and replaced by the summary under Annex 5. More in Nutrient flow balance repealed.

Fertiliser requirement in PhytAI

PhytAI calculates the nitrogen requirement under Annex 4 for arable and vegetable crops as well as grassland and stores the calculation with the legal basis for each line. Additions are treated as maximum values and deductions as minimum values; a recalculation requires a reason. When recording fertilisation, PhytAI compares against the calculated requirement, the 14-day deadline appears as a reminder, and the Annex 5 summary is built from the records. The assessment of individual cases stays with the farm and its advisors.

Frequently asked questions

Do I need an Nmin sample every year? Not necessarily. Besides analysis, the DüV allows reference values or calculation methods of the competent authority. For vegetables after vegetables, analysis is mandatory.

Is the calculation made per field? Per field or per management unit, i.e. for grouped areas with comparable conditions.

How long must I keep the documents? Seven years after the end of the fertiliser year.

Sources

This article reflects the situation on the date shown, based on the sources named, and is not legal advice. Laws, approvals, official decisions and the guidance of the competent authorities prevail.

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