Action

Add inorganic fertilizer (without planting)

How is the evidence assessed?
  • Effectiveness
    50%
  • Certainty
    30%
  • Harms
    15%

Source countries

Key messages

  • Three studies evaluated the effects of adding inorganic fertilizer (without planting) on peatland vegetation. Two studies were in bogs and one was in a fen meadow.
  • Vegetation cover (1 study): One replicated, randomized, paired, controlled, before-and-after study in a bog in New Zealand reported that fertilizing typically increased total vegetation cover.
  • Vegetation structure (1 study): One replicated, paired, controlled study in a fen meadow in the Netherlands found that fertilizing with phosphorous typically increased total above-ground vegetation biomass, but other chemicals typically had no effect.
  • Overall plant richness/diversity (1 study): One replicated, randomized, paired, controlled, before-and-after study in a bog in New Zealand reported that fertilizing typically increased plant species richness.
  • Growth (1 study): One replicated, controlled, before-and-after study in a bog in Germany found that fertilizing with phosphorous typically increased herb and shrub growth rate, but other chemicals had no effect.
  • Other (3 studies): Three replicated, controlled studies in a fen meadow in Germany and bogs in Germany and New Zealand reported that effects of fertilizer on peatland were more common when phosphorous was added, than when nitrogen or potassium were added.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated, paired, controlled study in 1994 in a degraded fen meadow in the Netherlands (van Duren et al. 1998) found that adding fertilizer increased plant biomass in 10 of 24 comparisons. The other comparisons were non-significant increases. After three months, above-ground vegetation biomass was greater in plots fertilized with phosphorous (80–370 g/m2) than in unfertilized plots (20–200 g/m2). The same was true for plots fertilized with phosphorous and nitrogen (220–460 g/m2) vs plots fertilized only with nitrogen (30–270 g/m2), and for plots fertilized with potassium, phosphorous and nitrogen (240–490 g/m2) vs plots fertilized with potassium and phosphorous or nitrogen (30–300 g/m2). In May 1994, 1 m2 plots (number not reported) were established in a rewetted fen meadow. Each plot received one fertilizer treatment: no fertilizer, N, P, K, N+P, N+K, P+K or N+P+K. Half of the plots were in an area stripped of topsoil. In August 1994, above-ground vegetation was harvested in a 60 x 60 cm quadrat in each plot, then dried and weighed.

    Study and other actions tested
  2. A replicated, controlled, before-and-after study in 1995 in a historically mined raised bog in Germany (Sliva et al. 1999) found that fertilizer increased seedling growth in 15 of 48 comparisons, all involving phosphorous, but had no effect in the other 33 comparisons. After four months, seedlings in plots fertilized with phosphorous (either alone or in combination with nitrogen and potassium) were significantly taller than seedlings in unfertilized plots in 15 of 24 comparisons (for which fertilized: 2–18 cm; unfertilized: 1–4 cm). Seedlings in plots fertilized only with nitrogen or potassium were never significantly taller than unfertilized seedlings (0 of 24 comparisons; fertilized: 1–5 cm; unfertilized: 2–4 cm). In spring 1995, six 16 m2 plots of recently rewetted bare peat received each fertilizer treatment: N, P, K, or a mix of all three. Eight additional plots were not fertilized. After four months, all seedlings of six plant species (four herbs and two shrubs) were measured in every plot.

    Study and other actions tested
  3. A replicated, randomized, paired, controlled, before-and-after study in 1998–2000 in a historically mined raised bog in New Zealand (Schipper et al. 2002) reported that fertilized plots typically contained more plant species and had greater vegetation cover than unfertilized plots. These results are not based on tests of statistical significance. After two years, fertilized plots contained more plant species than unfertilized plots in 11 of 12 comparisons (fertilized: 3–8 species; unfertilized: 2–6 species). Fertilized plots had greater cover of two peatland-characteristic plants: manuka Leptospermum scoparium in 6 of 9 comparisons (for which fertilized: 1–92%; unfertilized: 0–87%) and bamboo rush Sporadanthus ferrugineus in 5 of 9 comparisons (for which fertilized: 2–27%; unfertilized: 1–8%). Total vegetation cover was also higher in fertilized plots in 6 of 9 comparisons. In March 1998, twenty-four plots (each 25 m2) were established, in six blocks, on bare rewetted peat. Six plots (one random plot/block) received each fertilizer treatment: N, P, N+P, or none. None of these plots were sown. In June 2000, canopy cover was estimated for every plant species in each plot.

    Study and other actions tested
Please cite as:

Taylor N.G., Grillas P. & Sutherland W.J. (2019) Peatland Conservation. Pages 375-438 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

Peatland Conservation

This Action forms part of the Action Synopsis:

Peatland Conservation
Peatland Conservation

Peatland Conservation - Published 2018

Peatland Conservation

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, terrestrial mammals, forests, peatland and control of freshwater invasive species. More are in progress.

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