Add lime to reduce acidity and/or increase fertility

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

Effectiveness

50%
Certainty

15%
Harms

20%

Calculating overall effectiveness category

Background information and definitions

Peatland plant survival and growth is partly determined by the acidity of a peatland, or pH (Rydin & Jeglum 2013). Fen plants grow in alkaline to weakly acidic peat (approximately pH 6–8, similar to saliva, tap water or sea water). Bog plants grow in more acidic peat (approximately pH 4–5, similar to tomato juice or coffee). Lime (calcium and/or magnesium-rich chemicals) can be added if the peat becomes too acidic for a desired plant community. Liming can reduce acidity. It can also affect nutrient availability: nutrients such as phosphorous become locked away in acidic soils (Weil & Brady 2016).

Caution: The benefits and harms of liming are very context specific. Because fen plants require the least acidic conditions, liming is mostly used to manage fens and fen meadows. Liming may be useful in some bogs that have become extremely acidic (e.g. as a result of exceptionally acidic rain). In most bogs, liming could cause damage by removing natural acidity.

Related actions: rewetting, which may reverse drainage-related acidification of surface peat; restoring peatlands using multiple interventions, because lime is often used as part of a suite of interventions; add lime to complement planting.

_{Weil R.R. & Brady N.C. (2016) The Nature and Properties of Soils, Fifteenth Edition. Pearson, USA.}

_{Rydin H. & Jeglum J.K. (2013) The Biology of Peatlands, Second Edition. Oxford University Press, Oxford.}

Study locations

Key messages

One study evaluated the effects of liming (without planting) on peatland vegetation. The study was in a fen meadow. N.B. Liming is considered in different contexts here and here.
Vegetation structure (1 study): One replicated, controlled study in a fen meadow in the Netherlands found that liming increased overall vegetation biomass (mostly grass).

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, controlled study in 1994 in a degraded fen meadow in the Netherlands (van Duren et al. 1998) found that limed plots contained more plant biomass after three months than unlimed plots. This was true in plots that had previously been stripped of topsoil (limed: 40; unlimed: 20 g/m² biomass) and plots that had not been stripped (limed: 250; unlimed: 200 g/m² biomass). The biomass was mostly established, dominant, velvety bentgrass Agrostis canina (precise contribution not reported). In May 1994, ten 1 m² plots in a degraded, historically drained fen meadow were limed (approximately 500 g/m²). Ten additional plots were not limed. Five limed and five unlimed plots had been previously stripped of topsoil. In August 1994, above-ground vegetation was harvested in one 60 x 60 cm quadrat/plot, then dried and weighed.
Study and other actions tested
Referenced paper
van Duren I.C., Strykstra R.J., Grootjans A.P., ter Heerdt G.N.J. & Pegtel D.M. (1998) A multidisciplinary evaluation of restoration measures in a degraded Cirsio-Molinietum fen meadow. Applied Vegetation Science, 1, 115-130.

Please cite as:

Taylor, N.G., Grillas, P. & Sutherland, W.J. (2020) Peatland Conservation. Pages 367-430 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, 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:

Peatland Conservation

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