Stikstofgebruiksnorm 2025

This document provides a detailed explanation of the Dutch legal usage norm (gebruiksnorm) for nitrogen in 2025. It covers how the norm is calculated, the rules for catch crops and winter crops, and how the applied nitrogen counts towards this norm (opvulling).

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Calculating the Gebruiksnorm (Usage Norm)

How the Norm Works

The nitrogen usage norm sets the maximum total effective nitrogen (in kg N/ha) that can be applied to a field. The calculation follows a step-by-step process to find the most precise norm based on various factors.

Calculation Steps

1. Identify Main Crop: The main crop for 2025 is determined from your cultivation plan.
2. Determine Geographical Context: The field's location is used to check:
   • If it is in a Nutrient-Polluted Area (NV-gebied), which results in a stricter (lower) norm.
   • The dominant soil region (zand_nwc, zand_zuid, klei, veen, or loess).
3. Find the Standard Norm: The main crop is looked up in the official RVO Table 2 (or Tabel 2g for NV-gebieden).
4. Apply Specific Rules: The standard norm is refined with additional rules for certain crops:
   • Temporary Grassland (Tijdelijk grasland): The norm is adjusted based on the cultivation end date.
   • Potatoes (Aardappelen): The norm is adjusted based on the potato variety. See RVO Tabel 2c.
   • Maize (Maïs): The norm depends on the farm's derogation status.
   • Outdoor Flowers (Buitenbloemen): A higher norm is applied for specific varieties.
5. Select the Final Norm: The final value is selected based on the field's soil region and NV-gebied status.
6. Apply Nitrogen Usage Norm Reduction (Korting Stikstofgebruiksnorm): The norm can be reduced (korting) if catch crop (vanggewas) or winter crop (winterteelt) requirements were not met in the previous year on sand and loess soils.

How the FDM Calculator Determines the Norm

The fdm-calculator uses the calculateNitrogenUsageNorm function in fdm-calculator/src/norms/nl/2025/value/stikstofgebruiksnorm.ts, which relies on:

• stikstofgebruiksnorm-data.ts: Contains the data from RVO Tabel 2 and Tabel 2g.
• input.ts: Defines the required inputs, such as derogation status, location, and crop data.

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Vanggewassen en Winterteelten (Catch Crops and Winter Crops)

How the Rules Work

On sand and loess soils, the land must be covered during the winter to prevent nitrogen leaching. This can be achieved with a catch crop or a designated winter crop. Failure to comply results in a reduction of the nitrogen usage norm for the following year.

1. Winter Crop Exception

No reduction is applied if the main crop of the current year is a designated winter crop (winterteelt). These crops provide sufficient ground cover and nitrogen uptake. Official Source: RVO Tabel 2F Vanggewassen en winterteelten

2. Catch Crop Rules

If there is no winter crop, a catch crop (vanggewas) must be sown. The sowing date determines the reduction:

• No Reduction: Sown by October 1st.
• 5 kg N/ha Reduction: Sown between October 2nd and October 14th.
• 10 kg N/ha Reduction: Sown between October 15th and October 31st.
• 20 kg N/ha Reduction: No valid catch crop, sown on or after November 1st, or destroyed before February 1st.

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Grassland Renewal and Destruction Reductions

In 2025, specific nitrogen usage norm reductions (kortingen) apply when grassland is renewed or destroyed (scheuren). These reductions account for the nitrogen released during the decomposition of the sod.

1. Grassland Renewal (Gras-na-Gras)

When grassland is directly followed by new grassland, a reduction of 50 kg N/ha applies. This is only allowed within specific periods:

• Sand and Loess Soils: June 1st – August 31st.
• Clay and Peat Soils:
  • Derogation Farm + NV-Area: June 1st – August 31st.
  • Derogation Farm + Non-NV-Area: June 1st – September 15th.
  • Non-Derogation Farm: February 1st – September 15th.

2. Grassland Destruction (Gras-naar-Bouwland)

When grassland is replaced by Maize or specific Potato types, a reduction of 65 kg N/ha applies.

• Eligible Crops: Maize, Consumption Potatoes, and Factory Potatoes.
• Excluded Crops: Seed Potatoes (Pootaardappelen) do not trigger this reduction.
• Allowed Periods:
  • Sand and Loess Soils: February 1st – May 10th.
  • Clay and Peat Soils:
    • NV-Area: February 1st – March 15th.
    • Non-NV-Area: February 1st – May 31st.

How the FDM Calculator Implements These Rules

The fdm-calculator automatically detects grassland renewal and destruction events by analyzing the sequence of cultivations. It verifies the soil type, location (NV-gebied), and farm derogation status to apply the correct reduction.

If a renewal or destruction action is performed outside the legally allowed periods, the calculator will provide a descriptive error message to ensure compliance.

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Calculating the Opvulling (Filling)

How the Filling Works

The filling is based on the effective nitrogen (werkzame stikstof) applied, which is calculated using an efficiency coefficient (werkingscoëfficiënt).

Official Source: RVO Tabel 9 Werkzame stikstof landbouwgrond 2025

Calculation Formula

Effective Nitrogen (kg N) = Applied Amount (kg or ton) × Total Nitrogen Content (%) × Efficiency Coefficient (%)

Efficiency Coefficients (Werkingscoëfficiënten)

Mestsoort (Manure Type) & Herkomst (Origin)	Toepassing (Application)	Werkingscoëfficiënt (%)
Drijfmest en dunne fractie
Drijfmest van graasdieren (eigen bedrijf)	Met beweiding	45
	Zonder beweiding	60
Drijfmest van graasdieren (aangevoerd)		60
Drijfmest van varkens	Klei en veen	60
	Zand en löss	80
Overige drijfmest en dunne fractie		80
Vaste mest
Vaste mest van graasdieren (eigen bedrijf)	Bouwland (sep-jan)	30
	Overig met beweiding	45
	Overig zonder beweiding	60
Vaste mest van graasdieren (aangevoerd)	Bouwland (sep-jan)	30
	Overige	40
Vaste mest van varkens, pluimvee, nertsen		55
Overig
Compost / Champost		10 / 25
Kunstmest (Mineral fertilizer)		100

How the FDM Calculator Determines the Filling

The calculateNitrogenFilling function in fdm-calculator/src/norms/nl/2025/filling/stikstofgebruiksnorm.ts uses the fertilizer type, application method, and the coefficients from table-9.ts to calculate the effective nitrogen.