Action

Other biodiversity: Add compost to the soil

How is the evidence assessed?
  • Effectiveness
    65%
  • Certainty
    45%
  • Harms
    0%

Study locations

Key messages

Amphibians (0 studies)

Birds (0 studies)

Invertebrates (1 study): One replicated, controlled study from the USA, found no differences in invertebrate biodiversity between plots with or without added compost.

Mammals (0 studies)

Plants (4 studies): Four replicated, controlled studies (three randomized) from Italy, Spain, and the USA found more plant biomass in plots with added compost, compared to plots without added compost. One of these studies also found more plant cover and faster tree growth in plots with added compost. Another one also found sixteen species of rare plants only in plots with added compost. Another one found more plants in plots with added compost, compared to plots without added compost, in one of two years, but found similar numbers of plant species in plots with or without added compost.

Reptiles (0 studies)

Implementation options (0 studies)

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, controlled study in 2001–2003 in a degraded wood pasture in Catalonia, Spain, found more plant cover, more plant biomass, and faster tree growth in plots with added compost, compared to plots without added compost. Plants: More plant cover, more herbaceous biomass, and faster oak tree Quercus humilis growth were found in plots with added compost (cover: 89% vs 60%; biomass: 2,700 vs 1,700 kg dry weight/ha; growth: 41 vs 34 cm/year). Methods: Composted sewage sludge was added to five treatment plots (10 t dry matter/ha), but not five control plots (no compost). Each plot was 20 x 5 m. To restore the wood pasture, shrubs and small trees were crushed and scattered on the soil, and grass seeds were sown. Soil was collected in soil cores (10 cores/plot, 0–20 cm depth).

    Study and other actions tested
  2. A replicated, randomized, controlled, paired study in 2008–2011 in grazed annual grasslands in California, USA, found more plant biomass in plots with added compost, compared to plots without added compost. Plants: More plant biomass (measured as carbon) was found in plots with added compost (50–175 more g C/m2/year, above ground, dry weight). Methods: Composted organic green waste was added to three treatment plots (129 g total N/m2), but not six control plots, at each of two sites (coastal grassland in Nicasio and valley grassland in Browns Valley). The plots were 25 x 60 m. Above-ground plant biomass was measured at the end of the growing season (1,800 cm2/plot).

    Study and other actions tested
  3. A replicated, randomized, controlled study in 2007–2013 in a fallow field in Campania, Italy, found more plants and plant biomass in plots with added compost, compared to plots without added compost. Plants: More plants were found in plots with added compost, compared to plots without it, in one of two years (2013: 1,023 vs 473 individuals/m2). More plant biomass was found in plots with added compost, compared to plots without it, in both years (2012: 401 vs 119 g dry weight/m2; 2013: 301 vs 111). Similar numbers of plant species were found in plots with or without added compost (12–21 species). Methods: Compost was added to four treatment plots (2007–2009: 30 Mg/ha dry weight; 2010–2013: 15 Mg/ha dry weight), but not to four control plots. The plots were 10 x 5 m. The compost was made from municipal solid waste and urban yard trimmings. The compost was added, and plots were tilled, in April each year (20 cm depth). Horticultural crops were grown in 2007–2011. In March 2012 and 2013, all plants (spontaneous growth) were collected from 1 x 1 m quadrats in each plot.

    Study and other actions tested
  4. A replicated, controlled study in 2014 in 29 organic vegetable fields on the Central Coast, California, USA, found no differences in invertebrate biodiversity between plots with or without added compost. Invertebrates: Similar numbers of invertebrates and invertebrate families were found in plots with or without added compost (data reported as model coefficients). Methods: In each of 29 vegetable fields, compost was added to one plot, but not to one adjacent plot (5 x 5 m plots), 1–2 months before lettuces were planted (25 t compost/ha, made from cow, chicken, and green manures). Lettuces were planted in spring (5–28 March) and summer (30 May–5 July). Invertebrates (insects, springtails, and spiders) were collected in pitfall traps (three/plot, 7.5 cm diameter) and pan traps (two/plot, blue and yellow, 15 cm diameter) after 48 hours of trapping (one sample when lettuces were seedlings and one when mature).

    Study and other actions tested
  5. A replicated, randomized, controlled study in 2008–2012 in two grazed grasslands in California, USA, found more plant biomass in plots with added compost. Sixteen species of rare plants were found only in plots with added compost. Plants: Before grazing, more plant biomass was found in plots with added compost, compared to plots without it (coastal prairie: 41% more; valley grassland: 71% more). Higher plant diversity was found in plots with added compost, compared to plots without it, in one of eight comparisons (coastal prairie, 2009: 7.5 vs 6 species/m2; Shannon evenness index). In the valley grassland, increases in the relative abundance of three grass species, and decreases in that of two forb and one bulb species, were found in plots with added compost, compared to plots without it. In the coastal prairie, sixteen rare species (<5% of observations) were found only in plots with added compost. The abundance of an invasive grass (medusahead Elymus caput-medusae) was lower in plots with added compost, in one of four comparisons (13% lower abundance in plots with compost), but that of an invasive forb (Carthamus lanatus) was no different. Methods: In December 2008, composted green waste (7 kg dry matter/m2, 129 g N/m2, C to N ratio of 11) was added to three plots at each of two sites (one valley grassland and one coastal prairie, both dominated by non-native annuals), but compost was not added to three control plots at each site. All plots (25 x 60 m plots) were in cattle-grazed paddocks (15 ha, rotationally grazed to 84 g standing/m2).

    Study and other actions tested
Please cite as:

Shackelford, G. E., Kelsey, R., Robertson, R. J., Williams, D. R. & Dicks, L. V. (2017) Sustainable Agriculture in California and Mediterranean Climates: Evidence for the effects of selected interventions. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

Mediterranean Farmland

This Action forms part of the Action Synopsis:

Mediterranean Farmland
Mediterranean Farmland

Mediterranean Farmland - Published 2017

Mediterranean Farmland synopsis

What Works 2021 cover

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, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.


Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust