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BZ20 — Buffer Zone 20 metres (Randzoner 20 m)

Summary

Identical to BZ10 but a 20-metre buffer strip. Higher P erosion reduction, same N effect formula, higher potential area requirement.

Eligibility

PotV(i,"BZ20") = BZ20pot(i) × Countcy(i) × IniPotV(i) / 5 from PotentialBZ20.inc.

N Effect

NEffM(i,"BZ20") = leaching(i) − 12 — identical to BZ10. Retention type: SR.

P Effect

P_Effects_erosion(i,"BZ20") = erosion_field(i) × 0.75 [if BZ20Pot(i) > 0.2] Higher reduction factor than BZ10 (0.75 vs 0.62) reflecting wider strip.

Cost

CostM(i,"BZ20") = prodcost(i) — identical to BZ10. Wider strip means more area taken out of production → higher total cost (via PotV × CostM).

Mutual exclusions

Same as BZ10. Member of bz(j), mem(j). Cannot combine with IBZ (mutexc10).

Data sources

  • BZ potential: PotentialBZ20.inc
  • Surface retention: Surfret_2025on2018.inc
  • Leaching: leaching.inc
  • N + P effects, cost structure: hard-coded in TargetEcon 2026.gms

Catalog source

See BZ10 — both BZ10 and BZ20 are documented in the same catalog chapter ("Målrettede, brede og tørre randzoner", DCA Rapport nr. 174, p. 387–393). The catalog does not distinguish 10 m vs 20 m strips in terms of N effect (confirmed: width does not affect N reduction since groundwater transport dominates). The higher P reduction factor (0.75 vs 0.62) is consistent with the catalog's finding that wider strips provide greater P retention.