Action

Add fertilizer to soil before or after seeding/planting

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • Seventeen studies examined the effects of adding fertilizer to soil before or after seeding/planting on grassland vegetation. Nine studies were in North America, six studies were in Europe, one study was in China, and one was in Brazil.

VEGETATION COMMUNITY (3 STUDIES)

VEGETATION ABUNDANCE (13 STUDIES)

  • Overall abundance (8 studies): Six of nine replicated, controlled studies (five of which were also randomized and paired) in North America and Europe found that adding fertilizer alongside sowing or planting increased vegetation cover in all or some cases. Three studies found no change in vegetation cover or plant density.
  • Characteristic plant abundance (1 study): One replicated, randomized, paired, controlled study in the UK found that adding fertilizer and sowing seeds increased the abundance of specialist grassland species.
  • Sown/planted species abundance (3 studies): Two replicated, randomized, controlled studies in the USA found that adding fertilizer after sowing seeds did not alter the density of sown forbs. One replicated, randomized, paired, controlled study in the USA found that adding fertilizer after sowing seeds increased the cover but not the density of four sown plant species.
  • Grass abundance (1 study): One replicated, controlled study in the USA found that adding fertilizer and sowing seeds increased the biomass of three native grass species.

VEGETATION STRUCTURE (0 STUDIES)

OTHER (4 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, randomized, paired, controlled study in 1975–1980 in a former coal mine in Montana, USA (Holechek et al. 1982) found that adding fertilizer after sowing seeds increased the cover, but not the density, of four sown plant species compared to sowing without fertilizer. After five years, average cover of four sown plant species (thickspike wheatgrass Elymus lanceolatus, crested wheatgrass Agropyron cristatum, alfalfa Medicago sativa, and fourwing saltbush Atriplex canescens) was higher in plots where fertilizer was added and seeds were sown (10–43%) than in plots where seeds were sown without fertilizer (2–28%). However, the average density of each of the four sown species did not differ significantly between fertilized (12–88 plants/m2) and unfertilized plots (8–82 plants/m2). In 1975, eight 9 x 10 m plots were each sown with thickspike wheatgrass, crested wheatgrass, alfalfa, or fourwing saltbush seeds. Nitrogen and phospohorus fertilizer was applied to 12 of the plots, while 12 plots had no fertilizer applied. In July 1980, plant density and cover were estimated in at least 14–16 randomly placed 20 x 20–50 cm quadrats/plot.

    Study and other actions tested
  2. A replicated, paired, controlled study in 1986–1987 in a meadow in Hampshire, UK (Fenner & Spellerberg 1988) found that adding compost and sowing seeds of 12 grassland species did not increase survival of seedlings compared to sowing without fertilizer. During the first two growing seasons, the survival of seedlings did not differ between plots where compost was added to the soil alongside sowing of seeds and plots where seeds were sown without compost (no data presented). In March 1986, the meadow was sprayed with herbicide and plots dug to remove all dead vegetation. In three 2.6 m x 1.2 m plots, a 2.5 cm layer of compost was added to the soil surface and seeds of 12 grassland species were sown. In three other plots, no compost was added but seeds were sown. Survival of plants in each plot was recorded during the growing seasons in 1986 and 1987.

    Study and other actions tested
  3. A replicated, paired, controlled study in 1988–1991 in a largely unvegetated area on the island of Kahoʻolawe, USA (Warren & Aschmann 1993) found that adding fertilizer and sowing seeds increased vegetation cover compared to sowing without fertilizer. After 25 months, average vegetation cover was higher in plots where fertilizer was added and seeds sown (9–48%) than in plots where seeds were sown without fertilizer (3%). Plots where rates of fertilizer addition were higher also had greater vegetation cover (see original paper for details). In November 1988, the site was ploughed to a depth of 10 cm. In four 60 x 1.8 m plots in each of five blocks, fertilizer was added at three different rates and seeds (a mix of six grasses and one legume) were sown using a seed drill in. Seeds were sown without fertilizer in one plot/block. In January 1991, thirty 0.25-m2 quadrats were placed in each plot and vegetation cover estimated by eye.

    Study and other actions tested
  4. A replicated, randomized, paired, controlled study in 1992–1994 in a former mine in Minnesota, USA (Noyd et al. 1996) found that adding fertilizer before sowing seeds had a mixed effect on plant cover depending on fertilizer type and time since treatment. After two to three years, plant cover was higher in plots where compost was spread and seeds were sown (40–73%) than in plots where seeds were sown without compost (12–14%). However, after two years, plant cover did not differ significantly between plots where ammonium phosphate fertilizer was added (34–35%) and plots where it was not added (27%). After three years, plant cover was higher in plots where ammonium phosphate fertilizer was added (50–52%) than in plots where fertilizer was not added (43%). In May 1992, four blocks were established. In each block, compost was spread in two plots at a rate of 22.4–44.8 tonnes/ha, ammonium phosphate fertilizer was applied in two plots at a rate of 224–448 kg/ha, and one plot was left unfertilized. All plots were sown with a mixture of native plant species at a rate of 30.4 kg/ha. Plant cover was measured in all plots in August 1993 and 1994 along three 1-m wide transects.

    Study and other actions tested
  5. A replicated, randomized, paired, controlled study in 1993–1997 on three road verges in Colorado, USA (Paschke et al. 2000) found that adding fertilizer alongside seeding and planting increased vegetation cover in half of cases compared to seeding and planting alone. In three of six comparisons, vegetation cover was higher in plots where fertilizer was added, seeds were sown, and plants were planted (11.1–24.4%) than in plots where no fertilizer was added but seeding and planting was undertaken (2.7–8.6%). In two of six comparisons there was no significant difference (fertilized: 3.3–21.1%; unfertilized: 1.5–10.5%), and in one of six comparisons vegetation cover was lower in fertilized plots (fertilized: 0.6%; unfertilized: 8.9%). In October 1993 blocks, each with two plots, were established on three road verges. BioSol® organic fertilizer was added at a rate of 2242 kg/ha to one plot that was then sown with seeds of 13 grass, forb, and shrub species and planted with the same plant species. One plot was seeded and planted but no fertilizer was added. Vegetation cover in each plot was recorded in June 1994–1997.

    Study and other actions tested
  6. A replicated, randomized, controlled study in 1995–1997 at a former landfill site in Seattle, USA (Ewing 2002) found that adding fertilizer to soil after planting native prairie plants either reduced or did not alter the growth of seven plant species. After one year, prairie lupine Lupinus lepidus plants in fertilized plots had smaller diameters (average 35 cm) than those in unfertilized plots (average 40 cm). After 1–2 years, there was no significant difference in the growth of six other planted prairie species between fertilized and unfertilized plots (see original paper for data). In May 1995, twelve circular 4-m2 plots at the landfill site were each planted with four individuals of seven native prairie species. A granular NPK fertilizer was added to six plots, and six plots were left untreated. The landfill site had been decommissioned in 1966 and sown with grass in 1971. All surviving plants were measured in June and September 1995, and in July 1996 and 1997. Measurements included height, diameter, area, spread, and/or branch and stem length depending on the plant species.

    Study and other actions tested
  7. A replicated, randomized, paired, controlled study in 2000–2001 in a mining area in the Northwest Territories, Canada (Reid & Naeth 2005) found that adding fertilizer and sowing of seeds did not alter vegetation cover compared to seeding alone. Vegetation cover did not differ significantly between areas where fertilizer was added and seeds were sown (2–6%) and areas where no fertilizer was added but seeds were sown (4%). In August 2000, blocks were established containing four 5 × 2 m plots (number of blocks unclear from study) on areas of mining waste. Gypsum (2,173 kg/ha), rock phosphate (2,080 kg/ha) and calcium carbonate (1,667 kg/ha) were each added to one plot in each block, while one plot received no fertilizer. All plots were sown with the seeds of seven native grass species. In August 2000 and 2001, vegetation cover was assessed using three 50 × 20 cm quadrats/plot.

    Study and other actions tested
  8. A replicated, controlled study in 2004 at a severely disturbed serpentine site in northern California, USA (O'Dell & Claassen 2006) found that adding fertilizer before sowing seeds increased the biomass of three native grass species compared to sowing seeds without fertilizer. After five months, above-ground biomass of sown perennial grasses Chinook brome Bromus laevipes and squirreltail Elymus elymoides, and the annual grass small fescue Vulpia microstachys, was higher in plots with compost added (Chinook brome: 0.28 kg/m2; squirreltail: 0.20 kg/m2; small fescue: 1.19 kg/m2) compared to plots without compost (Chinook brome: 0.07 kg/m2; squirreltail: 0.03 kg/m2; small fescue: 0.01 kg/m2). In winter 2004, garden waste compost was added to nine 0.7-m2 plots. No compost was added to nine other plots. All plots were then tilled to a depth of 30 cm. Six plots were broadcast-seeded with each of Chinook brome (500 seeds/m2), squirreltail (300 seeds/m2) or small fescue (1,500 seeds/m2). All seeds were collected locally. Plots were harvested to calculate biomass 165 days after seeding.

    Study and other actions tested
  9. A replicated, randomized, paired, controlled study in 2005–2006 in a degraded steppe grassland in Hebei province, northern China (Liu et al. 2008) found that adding fertilizer and sowing seeds did not increase seedling emergence, survival or density compared to seeding alone. The percentage of seeds from which plants emerged did not significantly differ between areas where fertilizer was applied alongside seeding (51%) and areas that were seeded but no fertilizer was applied (45%). Similarly, after one year, there was no significant difference in seedling survival (fertilized: 3.1%; unfertilized: 2.6%) or seedling density (fertilized: 7.2 seedlings/m2; unfertilized: 9.5 seedlings/m2). In June 2005, seeds were sown in one hundred and twenty 2 × 2 m plots at a density of 400–1,200 seeds/m2 and soil compressed using a roller. Seeds were collected locally in autumn 2004. In 80 plots, fertilizer was applied, and in 40 plots, no fertilizer was applied. Plots were fenced to prevent damage from livestock and were sprayed with pesticides. Seedling density and survival was monitored in one 50 × 50 cm quadrat in each plot between June 2005 and August 2006.

    Study and other actions tested
  10. A replicated, randomized, paired, controlled study in 2006–2008 on five motorway verges in central Spain (Garcia-Palacios et al. 2010) found that adding fertilizer and sowing seeds of non-native plants increased plant cover and plant diversity in four of 10 comparisons compared to sowing alone. No statistical tests were carried out in this study. In four of 10 comparisons, plots where fertilizer was added and seeds were sown had on average greater overall plant cover (65–72%) and plant diversity (data reported as Shannon diversity index) than plots where seeds were sown but no fertilizer was added (plant cover: 61–71%). In the other six comparisons, sown plots with fertiliser added had lower or equal plant cover (49–55%) and diversity compared to sown plots without fertilizer added (plant cover: 49–65%) In December 2006, at each of five sites, two 1 × 1 m plots in each of six random blocks were sown with a commercial non-native seed mixture. A slow-release inorganic fertilizer was added to one plot/block in December 2006 and January 2008, while the other plot was not fertilized. In May 2007 and 2008, the cover of all plants was visually assessed in each plot.

    Study and other actions tested
  11. A replicated, controlled study in 2007–2008 in a landfill site and on the site of a former factory in north-west England, UK (Sparke et al. 2011) found that adding compost before sowing seeds increased vegetation cover compared to sowing without compost. No statistical analyses were carried out in this study. Vegetation cover was higher in areas where compost was added and seeds were sown (22–100%) than in areas where seeds were sown but no compost was added (8–92%). In May 2007, three blocks, containing fifteen 5 × 5 m plots, were established at each site. In each block, compost was added to soil in nine plots and no compost was added to soil in six plots. Wildflower seeds were sown in all plots at a rate of 4 g/m2. In April, July, August, September and October 2007, vegetation cover was estimated in two 1 × 1 m quadrats/plot.

    Study and other actions tested
  12. A replicated, randomized, paired controlled study in 2006–2007 on the site of a former steelworks in Flintshire, UK (Tandy et al. 2011) found that adding fertilizer and sowing seeds increased vegetation cover and cover of specialist grassland species compared to sowing without fertilizer. Vegetation cover was higher in areas where compost was added to the soil alongside sowing of seeds (38–64% cover) than in areas where no compost was added to the soil but seeds were sown (10–22%). Cover of specialist grassland species was higher in areas where compost was added to the soil alongside sowing (6.4% cover) than in areas with seeding but no compost (0.3%). Compost produced from green waste (biosolids) or paper was added to twenty-four 8 x 3 m plots using a muck spreader along with seeds of 24 grassland species. In six plots, no compost was added but seeds were sown. Wood chip was also added to all compost mixtures prior to the composting process. In July 2007, a 1 x 1 m quadrat was established in each plot and the percentage cover of each plant species was assessed.

    Study and other actions tested
  13. A replicated, randomized, controlled study in 2009–2010 in an agricultural field in southern Spain (Ballesteros et al. 2012) found that adding organic matter and sowing seeds did not alter plant density or species richness compared to sowing seeds without organic matter. In each of four comparisons, plant density and species richness were similar in plots where organic matter was added and seeds were sown (1–13 plants/m2; 0.3–2.1 species/0.25 m2) and in plots where organic matter was not added and seeds were sown (1–11 plants/m2; 0.2–1.8 species/0.25 m2). In November 2009, forty 5 x 5 m plots were sown with locally collected seeds of seven native grass and forb species. Organic matter (a commercial substrate) was randomly added to half of the plots (160 l/plot), while the other half had no organic matter added. Four different bedding materials were also applied to plots prior to seeding (see original paper for details). Plant density and species richness were estimated in July and October 2010 using fifteen randomly placed 0.5 x 0.5 m quadrats/plot.

    Study and other actions tested
  14. A replicated, randomized, controlled study in 2000–2006 in a former arable field in Minnesota, USA (Grygiel et al. 2012; same study site as Grygiel et al. 2014) found that adding fertilizer after sowing seeds did not alter the density of seeded or unseeded forb species compared to sowing without fertilizer. After 1–5 years, forb density did not differ significantly between plots where fertilizer was added and seeds were sown (seeded forbs: 30–137 plants/m2; unseeded forbs: 33–233 plants/m2) and plots where no fertilizer was added and seeds were sown (seeded forbs: 30–128 plants/m2; unseeded forbs: 32–186 plants/m2). In autumn 2000, two 2.8 × 2.8 m plots in each of ten blocks were tilled and seeded with a combination of native grasses and forbs at a rate of 25 kg/ha. In spring 2001, slow-release phosphorus fertilizer was added to one plot/block at a rate of 22 g/m2, while no fertilizer was added to the other plot. Vegetation was sampled in August 2002–2006 using four randomly placed 0.25-m2 quadrats/plot.

    Study and other actions tested
  15. A replicated, randomized, paired, controlled study in 1998–2010 in a former arable field in Minnesota, USA (Grygiel et al. 2014; same study site as Grygiel et al. 2012) found that adding fertilizer to soil after sowing seeds did not alter the density of sown native forb species. After 10–12 years, the average density of sown forb species did not differ significantly between plots where fertilizer was applied after seeds were sown (33 plants/m2) and plots where fertilizer was not applied after seeds were sown (40 plant/m2). In autumn 1998, two 4 x 3 m plots in each of five blocks were tilled and sown with a seed mixture containing four native grasses and 12 native forbs. In spring 1999, one plot/block had slow-release phosphorous fertilizer applied at a rate of 14 g/m2, while the other plot had no fertilizer applied. In July–August 2005–2010, the density of sown forb species was estimated in each of the 10 plots.

    Study and other actions tested
  16. A replicated, controlled, paired study in 2010–2012 in an arable field in Brazil (Silva et al. 2015) found that adding fertilizer and sowing tree seeds did not increase seedling survival compared to sowing without fertilizer. After 780 days, survival did not differ significantly for seedlings where fertilizer had been added (13–35%) and seedlings where it had not been added (27–52%). In November 2010, soil was ploughed in eight 1-m wide rows. In four of these rows, 30 seeds of six tree species were sown and 253 g of fertilizer and 84 g of phosphate/m were added. In the four other rows, seeds were sown but no fertilizer was applied. Holes were then refilled with soil and a straw mulch was spread. Seedling germination and survival was recorded for each plant after 42, 84, 126, 217, 398, and 780 days.

    Study and other actions tested
  17. A replicated, controlled study in 2010–2012 in an experimental field in Tuscany, Italy (Vannucchi et al. 2015) found that adding fertilizer before sowing seeds did not alter plant density or diversity compared to sowing alone. Plant density did not differ significantly between areas where compost was added to the soil and seeds were sown, and areas where seeds were sown but no compost was added (no data reported). The same pattern was seen for plant diversity (data reported as diversity indices). In October 2010, eight 2 × 1 m boxes were filled with soil collected from a nearby floodplain. Compost derived from household waste was added to four boxes at a rate of 2 kg/m2, while no compost was added to the other four boxes. In November 2010, seeds of 26 native herb species were sown and the soil was raked. Any weeds that grew were removed. The number of plants in each plot was counted in July and October 2011 and plant diversity was assessed in July and October 2011 and 2012.

    Study and other actions tested
Please cite as:

Martin, P.A., Ockendon, N., Berthinussen, A, Smith, R.K. and Sutherland W.J. (2021) Grassland Conservation: Global evidence for the effects of selected interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

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