Add inorganic fertilizer: brackish/salt marshes
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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.
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.
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