Crop production: Add slurry to the soil

Overall effectiveness category Beneficial
Number of studies: 6
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How is the evidence assessed?

Effectiveness

90%
Certainty

75%
Harms

0%

Calculating overall effectiveness category

Study locations

Key messages

Crop yield (6 studies): Six replicated, randomized, controlled studies from Spain found higher crop yields in plots with added pig slurry, compared to plots without it, in some comparisons.

Crop quality (0 studies)

Implementation options (4 studies): Two replicated, randomized, controlled studies from Spain found similar crop yields in plots with digested pig slurry, compared to untreated pig slurry. One replicated, randomized, controlled study from Spain found lower crop yields in plots with less pig slurry, compared to more, but another found similar crop yields with different amounts of pig slurry.

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, randomized, controlled study in 2009 in a rainfed barley field in Spain found higher crop yields in plots with added slurry, compared to plots without it. Crop yield: Higher barley yields were found in plots with added slurry, compared to plots without it, in one of two comparisons (1,508 vs 972 kg/ha). Implementation options: Similar barley yields were found in plots with untreated slurry or digested slurry (1,125 vs 1,508 kg/ha). Methods: Plots (30 m²) had no fertilizer or pig slurry (anaerobically-digested or untreated), which was applied in January 2006 (125 kg N/ha; three plots for each) and incorporated into the soil (0–5 cm depth) using a roto-cultivator. Phosphate and potassium (75 and 40 kg/ha, respectively) were added to all plots.
Study and other actions tested
Referenced paper
Meijide A., Díez J.a., Sánchez-Martín L., López-Fernández S. & Vallejo a. (2007) Nitrogen oxide emissions from an irrigated maize crop amended with treated pig slurries and composts in a Mediterranean climate. Agriculture, Ecosystems & Environment, 121, 383-394.
A replicated, randomized, controlled study in 2006 in a barley field in the Henares river basin, Spain, found higher crop yields in plots with added slurry, compared to plots without it. Crop yield: Higher barley yields were found in plots with added slurry, compared to plots without it, in one of two comparisons (digested slurry: 2,381 vs 1,825 kg grain and straw/ha). Implementation options: Similar barley yields were found in plots with digested slurry or untreated slurry (2,381 vs 2,117 kg grain and straw/ha). Methods: There were three plots (30 m²) for each of two treatments (anaerobically digested thin fraction of pig slurry or untreated pig slurry) and there were three control plots (no slurry). Slurry was applied at a rate of 125 kg available N/ha, in January. Plots were cultivated (5 cm depth) to incorporate the slurry. Barley was planted in January and harvested in June.
Study and other actions tested
Referenced paper
Meijide A., Cárdenas L.M., Sánchez-Martín L. & Vallejo a. (2010) Carbon dioxide and methane fluxes from a barley field amended with organic fertilizers under Mediterranean climatic conditions. Plant and Soil, 328, 353-367.
A replicated, randomized, controlled study in 2000–2003 in an irrigated maize field in Spain found higher crop yields in plots with added slurry, compared to plots without it. Crop yield: Higher maize yields were found in plots with added slurry, compared to plots without it, in two of three comparisons (7–12 vs 6–7 Mg/ha). Methods: Plots (3.8 x 2.5 m) had added slurry (30, 60, 90, or 120 Mg/ha) or no fertilizer (three plots for each). Maize was harvested in November each year.
Study and other actions tested
Referenced paper
Yagüe M. R. & Quílez D. (2010) Cumulative and residual effects of swine slurry and mineral nitrogen in irrigated maize. Agronomy Journal, 102, 1682-1691.
A replicated, randomized, controlled study in 2000–2005 in an irrigated barley-maize field in Spain found higher crop yields in plots with added slurry, compared to plots without it. Crop yield: Higher yields were found in plots with added slurry, compared to plots without it (4–6 vs 3 Mg/ha). Methods: Plots (3.8 x 2.5 m) had added slurry (30, 60, 90, or 120 Mg/ha) or no fertilizer (three plots for each) in 2000–2003. Phosphorus (120 kg P₂O₅/ha) and potassium (180 kg KCl/ha) were added to all plots in 2003 and 2004. Barley was sown in December 2003 and harvested in June 2004. Maize was sown in July 2004 and harvested in December.
Study and other actions tested
Referenced paper
Yagüe M. R. & Quílez D. (2013) Residual effects of fertilization with pig slurry: double cropping and soil. Agronomy Journal, 105, 70-78.
A replicated, randomized, controlled study in 2010–2013 in rainfed barley fields in Spain found higher crop yields in plots with added slurry, compared to plots without it. Crop yield: Higher barley yields were found in plots with added slurry (4,657–5,335 vs 2,359 kg/ha). Implementation options: Lower barley yields were found in plots with less slurry, compared to more slurry (4,657 vs 5,335 kg/ha). Methods: Plots (40 x 12 m) had added slurry (75 or 150 kg N/ha) or no fertilizer (three plots for each). Plots had conventional tillage (mouldboard plough: 25 cm depth; cultivator: 15 cm depth) or no tillage. Barley was harvested in June.
Study and other actions tested
Referenced paper
Plaza-Bonilla D., Cantero-Martínez C., Bareche J., Arrúe J. L. & Álvaro-Fuentes J. (2014) Soil carbon dioxide and methane fluxes as affected by tillage and N fertilization in dryland conditions. Plant and Soil, 381, 111-131.
A replicated, randomized, controlled study in 2003–2004 in an irrigated maize field in Spain found higher crop yields in plots with added pig slurry, compared to plots without it. Crop yield: Higher maize yields were found in plots with added pig slurry (16–18 vs 10 Mg/ha). Implementation options: Similar crop yields were found in plots with different amounts of added slurry (30, 60, 90, 120 Mg/ha) (16–18 Mg/ha). Methods: Plots (30 x 40 m) had pig slurry (30, 60, 90, or 120 Mg/ha) or no fertilizer (three plots for each). Slurry was immediately covered after application. Lysimeters (2.6 x 2 m; 1.5 m depth), were installed in each plot, five years before the study. Each lysimeter was drip-irrigated, simulating flood irrigation (May to mid-September, with 7–12 intervals). Soil samples were collected after harvest (0–120 cm depth).
Study and other actions tested
Referenced paper
Yagüe M. R. & Quílez D. (2015) Pig slurry residual effects on maize yields and nitrate leaching: a study in lysimeters. Agronomy Journal, 107, 278-286.

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?

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This Action forms part of the Action Synopsis:

Mediterranean Farmland

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