Data: DCA_Levering_Diff_effekt_kv_lstofvirkemidler_REVIDERET_300925.pdf¶
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Content¶
Advisory note commissioned by SGAV (Styrelsen for Grøn Arealomlægning og Vandmiljø) providing both nationally averaged and geographically differentiated rootzone N effects for selected N measures. The differentiated effects cover 108 coastal catchments (kystvanddeloplande).
This is the primary scientific source behind differentiation_effects.inc used in TargetEcon 2026.
Full citation¶
Rolighed, J., Thers, H., Larsen, S.U., Blicher-Mathiesen, G., Eriksen, J. 2025. Differentieret effekt af kvælstofvirkemidler. Rådgivningsnotat fra DCA – Nationalt Center for Fødevarer og Jordbrug, Aarhus Universitet. 45 sider. Commissioned by SGAV journal no. 2025-0821072. Originally delivered 25.06.2025; revised 30.09.2025.
Commissioning context¶
SGAV requested this note to support: - MARS (IT tool used by municipalities and local green tripartite groups for N measure planning) - Calculation of Vandområdeplan 4 (VP4, Denmark's 4th Water Action Plan) - Updated baseline: "Opdatering af baseline 2027" (Blicher-Mathiesen et al., 2023)
Measures covered and key findings¶
Efterafgrøder (CCS — catch crops)¶
No change from the 2020 catalog (Eriksen et al., 2020). Still: 12/24/32/45 kg N/ha by soil type and livestock density. A revised NLES5-based calculation would require a separate project. The document confirms the 2020 values remain the operational standard.
Skovrejsning (FO — forestry)¶
- Residual N leaching from planted forest: 8 kg N/ha (range 5–15)
- National N effect on omdrift: 50 kg N/ha (ref. 58 kg/ha 2021 baseline − 8 kg = 50)
- This is slightly lower than the 2020 catalog's 53 kg/ha, reflecting the updated 2021 baseline (58 kg/ha vs. earlier ~61 kg/ha)
- Differentiated values for 108 catchments in Appendix 1 (largest effects in West Denmark where reference leaching is highest)
Kortvarig brak (SA — temporary set-aside)¶
Major update with new empirical data from the BRAK project (AU Foulum and Flakkebjerg, 2021–2024). Three brak sub-types:
| Brak type | N leaching from brak | N effect (nationally) | Area share |
|---|---|---|---|
| Slåningsbrak (grass), 5 yr | 12 kg N/ha (SD 11) | 46 kg N/ha | 46% |
| Slåningsbrak (volunteer crops), 2 yr | 29 kg N/ha (SD 21) | 29 kg N/ha | 32% |
| Blomsterbrak, 2 yr | 34 kg N/ha (SD 8) | 24 kg N/ha | 22% |
| Area-weighted average | 22 kg N/ha | 34 kg N/ha | 100% |
Reference leaching 2021 average: 58 kg N/ha on omdrift.
Key findings from BRAK project: - Leaching from slåningsbrak (grass) is very low and close to 12 kg N/ha residual, barely declining over 5 years of brak - Blomsterbrak has substantially higher leaching (~34 kg N/ha) than slåningsbrak - Leaching in the first year is higher than subsequent years for slåningsbrak (grass/Tunø data) - Differentiated values for 108 catchments in Appendix 2 (Tables B2.1–B2.3)
Range across 108 catchments (slåningsbrak, grass):
- SA N effect: 24–62 kg N/ha (lowest in Eastern Denmark islands/low-leaching catchments, highest in West Jutland/high-leaching catchments)
- The model's differentiation_effects.inc corrections range −6 to −27 across ~97 catchments — these represent catchment-specific residual leaching values derived from an earlier version of this analysis (May 2025 delivery, before this September 2025 revision)
Permanent udtagning (LRh — permanent set-aside)¶
- Residual N leaching: 12 kg N/ha (from the mean of available measurements)
- National N effect on omdrift: 46 kg N/ha (58 − 12; Table 9)
- National N effect on permanent grass: 0 kg N/ha (12 − 12; taking out permanent grass gives no additional N reduction)
- Differentiated values for 108 catchments in Appendix 3 (Table B3.1)
Range for the 13 LRh catchments used in TargetEcon (series 217–238):
| Catchment | Permanent udtagning residual | Landbrug 2021 reference | N effect (omdrift) |
|---|---|---|---|
| 217 Lillebælt, Bredningen | 27 kg N/ha | 48 | 21 (3–40) |
| 219 Aarhus Bugt syd | 18 kg N/ha | 43 | 25 (12–38) |
| 221 Skagerrak | 31 kg N/ha | 68 | 37 (15–59) |
| 222 Kattegat, Aalborg Bugt | 29 kg N/ha | 66 | 37 (17–58) |
| 224 Nordlige Lillebælt | 23 kg N/ha | 50 | 27 (11–43) |
| 225 Nordlige Kattegat, Ålbæk Bugt | 30 kg N/ha | 68 | 38 (16–59) |
| 231 Lillebælt, Snævringen | 26 kg N/ha | 47 | 21 (2–39) |
| 232 Nissum Bredning | 36 kg N/ha | 61 | 25 (0–51) |
| 233 Kås Bredning og Venø Bugt | 34 kg N/ha | 64 | 30 (5–54) |
| 234 Løgstør Bredning | 29 kg N/ha | 59 | 30 (9–50) |
| 235 Nibe Bredning og Langerak | 28 kg N/ha | 63 | 35 (15–55) |
| 236 Thisted Bredning | 36 kg N/ha | 64 | 28 (2–54) |
| 238 Halkær Bredning | 29 kg N/ha | 58 | 29 (9–50) |
The 13 LRh catchments are all in the Northern Jutland / Limfjorden region and along central-western Jutland (Nissum, Thisted, Nibe, etc.), consistent with areas where high-land retirement is policy-relevant.
Note: The document shows "permanent udtagning residual" values of 18–36 kg N/ha for these catchments. This is the rootzone leaching from the set-aside land itself — higher than the national average of 12 kg N/ha because these are high-reference-leaching catchments. The model's differentiation_effects.inc uses corrections of −7 to −15, representing the catchment-specific residual (=12 minus some spatial adjustment).
National efficiency comparison (Table 9, p.24)¶
| Measure | Reference leaching (omdrift) | Residual leaching | N effect (rootzone) |
|---|---|---|---|
| CCS | — | Not revised | 12/24/32/45 |
| FO (skovrejsning, omdrift) | 58 | 8 | 50 |
| SA (1-yr brak, omdrift) | 58 | 22 | 34 |
| LRh (permanent udtagning, omdrift) | 58 | 12 | 46 |
| LRh (permanent udtagning, permanent grass) | 12 | 12 | 0 |
Method¶
All calculations use: - NLES5 (Børgesen et al., 2020): empirical Danish N leaching model - Reference leaching from Rolighed (2023): the "Opdatering af baseline 2027" per-catchment reference values - Differentiation: reference varies by catchment; N effect = catchment reference − measure residual leaching
Relationship to differentiation_effects.inc¶
✅ Resolved (2026-04-05): differentiation_effects.inc was updated by the model developer to align with this document's September 30, 2025 revision. The updated file now covers 108 catchments for both LRH and SA (previously 13 for LRH, ~97 for SA). The per-catchment values match the September 2025 delivery.
Key change in updated file vs prior version: - LRH expanded from 13 catchments (corrections 7–15) to 108 catchments (corrections 6–18); the 13 original Limfjorden catchment values are unchanged - SA expanded from ~97 to 108 catchments; correction range (6–27) and outlier catchments (57, 139 at −27) unchanged
Used by¶
differentiation_effects.inc→ N effects for SA, LRh (and possibly FO) in TargetEcon 2026- Potentially MARS tool (not TargetEcon itself)