Soil aggregation and soil organic carbon stabilization: effects of management in semiarid Mediterranean agroecosystems

Published source details Álvaro-Fuentes J., Cantero-Martínez C., López M. V., Paustian K., Denef K., Stewart C. E. & Arrúe J. L. (2009) Soil aggregation and soil organic carbon stabilization: effects of management in semiarid Mediterranean agroecosystems. Soil Science Society of America Journal, 73, 1519-1529.
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This study is summarised as evidence for the following.

	Action	Category
	Soil: Use no tillage instead of reduced tillage Action Link
	Soil: Use crop rotations Action Link
	Soil: Use no tillage in arable fields Action Link
	Soil: Use reduced tillage in arable fields Action Link
	Change tillage practices Action Link

Soil: Use no tillage instead of reduced tillage

A replicated, randomized, controlled study in 2003 in rainfed farmland in the Ebro river valley, Spain, found greater soil aggregation in plots with no tillage, compared to reduced tillage. Soil erosion and aggregation: More large aggregates were found in soils with no tillage, compared to reduced tillage, in four of six comparisons (0–10 cm depth, water-stable aggregates >2000 µm: 0.08–0.15 vs 0.02–0.03 g aggregate/g soil). Methods: No tillage or reduced tillage was used on three plots each (10 x 33 m). A chisel plough was used for reduced tillage (25–30 cm depth). Herbicide was used for no tillage. Soil samples were collected with a flat spade (0–20 cm depth) in July 2003.
Soil: Use crop rotations

A replicated, randomized, controlled study in 2003 in a rainfed barley field in the Ebro river valley, Spain, found less organic matter, but inconsistent differences in stability, in soils with barley-fallow rotations, compared to continuous barley. Organic matter: Less organic carbon was found in soils with barley-fallow rotations, compared to continuous barley, in one of three comparisons (0–20 cm depth: 2,306 vs 2,743 g C/m²). Soil erosion and aggregation: Fewer large aggregates were found in soils with barley-fallow rotations, compared to continuous barley, in one of nine comparisons (water-stable aggregates >2,000 µm, 0–5 cm depth: 0.09 vs 0.15 g aggregate/g soil), but more were found in one of nine comparisons (53–250 µm, 0–5 cm depth: 0.6 vs 0.5 µm). Methods: Barley was grown in rotation with fallows on three plots, but barley was grown continuously on three other plots. Plots were 33 x 10 m. Soil samples were collected with a flat spade (0–20 cm depth) in July 2003.
Soil: Use no tillage in arable fields

A replicated, randomized, controlled study in 2003–2004 in rainfed farmland in the Ebro river valley, Spain, found more stable soils in plots with no tillage, compared to conventional tillage. Soil erosion and aggregation: More large aggregates were found in soils with no tillage, compared to conventional tillage (in Selvanera, 0–20 cm depth, aggregates >2,000 µm: 0.17–0.37 vs 0.06–0.15 g aggregate/g soil). More large water-stable aggregates were also found in soils with no tillage, compared to conventional tillage, in four of six comparisons (in Peñaflor, 0–10 cm depth, water-stable aggregates >2,000 µm: 0.08–0.15 vs 0.01–0.03 g aggregate/g soil). Methods: No tillage or conventional tillage was used on six plots each (three in Selvanera, 7 x 50 m each; three in Peñaflor, 10 x 33 m each). Herbicide was used for no tillage. In Selvanera, a subsoil plough (50 cm depth) and a cultivator (15 cm depth) were used for conventional tillage. In Peñaflor, a mouldboard plough was used for conventional tillage (30–35 cm depth). Soil samples were collected with a flat spade (0–20 cm depth) in July 2003 and 2004.
Soil: Use reduced tillage in arable fields

A replicated, randomized, controlled study in 2003 in rainfed farmland in the Ebro river valley, Spain, found similar amounts of soil aggregation in plots with reduced tillage, compared to conventional tillage. Soil erosion and aggregation: Similar amounts of large aggregates were found in soils with reduced tillage or conventional tillage (0–20 cm depth: water-stable aggregates >2,000 µm: 0.01–0.03 g aggregate/g soil). Methods: Conventional tillage or reduced tillage was used on three plots each (10 x 33 m). A mouldboard plough was used for conventional tillage (30–35 cm depth). A chisel plough was used for reduced tillage (25–30 cm depth). Soil samples were collected with a flat spade (0–20 cm depth) in July 2003.
Change tillage practices

A controlled experiment in 2003-2004 on silty clay loam soil in Peñaflor, Spain (Álvaro-Fuentes et al. 2009) found that soil organic carbon was more than 30% higher in topsoil under no-tillage (853 g/m² continuous barley, 671 g/m² barley-fallow) compared to conventional tillage (547 g/m² continuous barley, 490 g/m² barley-fallow). Organic carbon levels in large aggregated soil particles was greater under no-tillage (4.1 g C/kg) than conventional tillage (1.2 g C/kg) in continuous barley, indicating improved soil structure, but did not differ in the barley/fallow rotation. Three tillage systems (no-tillage with a direct driller and herbicide treatment, reduced tillage with a chisel plough to 30 cm, conventional tillage with a mouldboard plough to 35 cm and a pass with a tractor-mounted scrubber), contained two cropping systems: barley Hordeum vulgare/fallow rotation, continuous barley. In each plot, 12 soil cores were taken to 20 cm depth (size/number of plots not specified). Total soil organic carbon was measured.