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PPC — Permanent Plant Cover (Permanent plantedække på erosionstruede arealer)

Summary

Establishment of permanent grass or herbaceous vegetation strips on erosion-prone slopes — either as contour buffer strips (bufferstriber) or as grassed waterways (græsbevoksede vandveje). Intercepts and retains particulate P and sediment transported by overland flow before it reaches watercourses. PPC is the strongest single erosion-targeting field measure in the model.

Eligibility

PotV(i,"PPC") = Countcy(i) × IniPotV(i) / 5

N Effect

None (PPC is not in any N effect matrices).

P Effect

P_Effects_erosion(i,"PPC") = erosion_field(i) × 0.9   [if PotV > 0]
90% reduction in field erosion P loss. This is the highest erosion reduction factor of any single field measure.

Cost

CostM(i,"PPC") = 80 + 0.1 × prodcost(i) DKK/ha/yr Low flat cost plus a small fraction of the opportunity cost. PPC is one of the cheapest P measures.

Mutual exclusions

Member of mem(j), pho(j). Can be combined with NPB10 or NPB20 in the PPC_NPB10 and PPC_NPB20 combined measures (with 10% synergy discount on NPB cost).

Notes

  • PPC combined with NPB gives additional P reduction for a discounted cost — see Combined measures.
  • PPC alone only reduces erosion (not macropore or matrix). Where macropore loss dominates, NPB alone may be more cost-effective.
  • PPC targets the same fields as BZ (buffer zones), but BZ is positioned along watercourses while PPC is positioned on slope gradients within fields.

Data sources

  • Erosion P loss (erosion_field(i)): erosion_field.inc
  • Opportunity cost (prodcost(i)): Cost_new_avg.inc + MarkAccess2.inc
  • P effect factor (0.9), cost formula: hard-coded in TargetEcon 2026.gms

Catalog source

SR379 — DCE Scientific Report no. 379 (Andersen et al., 2020): Chapter "Permanent plantedække på erosionstruede arealer og som barriere i landskabet" (p. 30–39). Authors: Goswin Heckrath, Preben Olsen et al.

Mechanism: Permanent vegetation strips on steep or erosion-prone slopes trap soil particles (and adsorbed particulate P) as overland flow slows and infiltrates. Three types: randzoner (separate BZ measure), bufferstriber (contour strips), and græsbevoksede vandveje (grassed waterways). The model's PPC corresponds to types 2 and 3.

P effect from catalog: - Particulate P removal: 50–97% (international and Danish studies) - Dissolved P removal: 20–30% (more variable, -83% to +95%) - Sediment removal: 40–100% - The model's 0.90 (90%) erosion reduction factor is at the upper end of the range — representative of well-placed permanent strips on clearly erosion-prone fields.

Target area: Fields with >10° slope. Catalog estimates ~5,500 ha in Denmark meet this threshold. Most are sandy soils (JB1-4: 64%) with some clay (JB5-11: 34%).

Cost from catalog: - Opportunity cost: 1,193 DKK/ha/yr (sandy soil) — 3,027 DKK/ha/yr (clay) - The model's cost formula 80 + 0.1 × prodcost(i) combines a flat setup cost with a fraction of opportunity cost. This is a compressed version of the catalog's income-loss approach.

N side effect: Small — the catalog notes that N infiltrating buffer strips can be removed via denitrification or plant uptake, but given the limited area the quantitative N effect is negligible.

Confidence: Not explicitly scored but the mechanism is well-documented internationally; Danish erosion data are limited.

  • NPB10, NPB20 — combined in PPC_NPB10 and PPC_NPB20 (synergy discount)
  • OT — tillage-based alternative; 50% erosion reduction (vs 90% for PPC)
  • BZ10 — buffer zones along watercourses (related erosion concept; 62%)
  • Combined measures
  • P loss pathways — erosion pathway that PPC addresses
  • P Reduction — PPC erosion effect equation
  • Cost concepts — 80 + 10% prodcost; among cheapest P measures