Add inorganic fertilizer: brackish/salt marshes

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

20%
Certainty

30%
Harms

3%

Calculating overall effectiveness category

Background information and definitions

Fertilizers can be used to manage nutrient availability and may speed up revegetation. Plant growth might be limited by a lack of nutrients overall, or of a specific nutrient, after drainage, mining, vegetation harvest or pollution. When one or two nutrients are overabundant, invasive plant species may benefit more than native species. Adding the less abundant nutrients may shift the competitive balance back towards native species (Tilman et al. 1999; Perry et al. 2004). Commonly added nutrients include nitrogen (N), phosphorous (P) and/or potassium (K). It may be sensible to add fertilizer when the focal site is not flooded, to reduce the risk of it dissolving or being washed away.

The effects of this action will be heavily dependent on the study context, especially initial site nutrient levels and the amount of fertilizer added. Adding fertilizer when nutrients are already abundant could cause more harm than good, encouraging the growth of undesirable plants or algae and even inhibiting plant growth (Weinbaum et al. 1992). Accordingly, studies testing the effects of nutrient enrichment as a threat (i.e. enrichment above normal or desirable levels) are not summarized as evidence.

Related actions: Add inorganic fertilizer to complement planting; Stimulate microbial breakdown of oil, including through fertilization.

^{Perry L.G., Galatowitsch S.M. & Rosen C.J. (2004) Competitive control of invasive vegetation: a native wetland sedge suppresses Phalaris arundinacea in carbon-enriched soil. Journal of Applied Ecology, 41, 151–162.}

^{Tilman E.A., Tilman D., Crawley M.J. & Johnston A.E. (1999) Biological weed control via nutrient competition: potassium limitation of dandelions. Ecological Applications, 9, 103–111.}

^{Weinbaum S.A., Johnson R.S. & DeJong T.M. (1992) Causes and consequences of overfertilization in orchards. HortTechnology, 2, 112–121.}

Study locations

Key messages

One study evaluated the effects, on vegetation, of adding inorganic fertilizer to restore or create brackish/salt marshes. The study was in Canada.

VEGETATION COMMUNITY

VEGETATION ABUNDANCE

Characteristic plant abundance (1 study): One replicated, paired, controlled, before-and-after study in salt-contaminated bogs in Canada found that adding fertilizer had no significant effect on cover of salt marsh vegetation, in unplanted plots, after one year.

VEGETATION STRUCTURE

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

A replicated, paired, controlled, before-and-after study in 2011–2012 in two salt-contaminated bogs in New Brunswick, Canada (Emond et al. 2016) found that fertilizing without introducing salt marsh vegetation had no significant effect on cover of salt marsh plants. After one year, cover of salt marsh plant species was very low in both fertilized bog plots (0% cover) and unfertilized bog plots (<0.1% cover). Methods: In summer 2011, sixteen 9-m² plots were established (in four sets of four) on bare, salt-contaminated peat. Eight plots (two plots/block) were fertilized with rock phosphate, spread across the plot surface (50 g/m²) or placed in 49 holes/plot (9 g/hole). The other eight plots were not fertilized. Half of the fertilized and unfertilized plots were also limed, but no vegetation was introduced to any of the plots. In July 2012, cover of salt marsh plants (i.e. species present in a nearby salt marsh) was recorded in one 4-m² quadrat/plot.
Study and other actions tested
Referenced paper
Emond C., Lapointe L., Hugron S. & Rochefort L. (2016) Reintroduction of salt marsh vegetation and phosphorus fertilisation improve plant colonisation on seawater-contaminated cutover bogs. Mires and Peat, 18, Article-17.

Please cite as:

Taylor N.G., Grillas P., Smith R.K. & Sutherland W.J. (2021) Marsh and Swamp Conservation: Global Evidence for the Effects of Interventions to Conserve Marsh and Swamp Vegetation. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation

Related Actions

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Reprofile/relandscape: freshwater marshes Action Link	Likely to be beneficial	13	Synopsis Link
Facilitate tidal exchange to restore/create freshwater marshes from other land uses Action Link	No evidence found (no assessment)	0	Synopsis Link
Add inorganic fertilizer: freshwater marshes Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link