Carbon accumulation in soil. Ten-year study of conservation tillage and crop rotation in a semi-arid area of Castile-Leon, Spain

Published source details Sombrero A. & de Benito A. (2010) Carbon accumulation in soil. Ten-year study of conservation tillage and crop rotation in a semi-arid area of Castile-Leon, Spain. Soil and Tillage Research, 107, 64-70.
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This study is summarised as evidence for the following.

	Action	Category
	Soil: Use crop rotations Action Link
	Change tillage practices Action Link

Soil: Use crop rotations

A replicated, controlled study in 1994–2001 in a rainfed cereal field in the Duero valley, northern Spain, found similar amounts of organic matter in soils with or without crop rotations. Organic matter: Similar amounts of organic carbon were found in soils with or without crop rotations (36–42 Mg/ha). Methods: Cereals (wheat and barley) were grown continuously (one plot/year), in rotation with vetch Vicia sativa (two plots/year: one cereal, one vetch), or in rotation with fallow (two plots/year: one cereal, one fallow), in each of three tillage treatments (conventional, reduced, or no tillage), in each of four blocks. Each plot was 450 m², and there were 60 plots in total (five plots/three treatments/four blocks). The cereals were fertilized (8-24-8 NPK: 400 kg/ha; ammonium sulphate: 300 kg/ha). Herbicide was used on all plots. Soil samples were collected in October 1994, 1997, and 2000 (three samples/plot, 0–30 cm depth), before tillage in November.
Change tillage practices

A controlled replicated experiment from 1995 to 2004 on a loamy-clay soil in Burgos, Spain (Sombrero & de Benito 2010) found that after 10 years, soil organic carbon was 25% greater under no-tillage than conventional tillage, 16% greater than under minimal tillage, and 17% higher in minimal tillage compared to conventional tillage. Tillage treatment affected soil organic carbon levels more than crop rotation. There were 15 plots (450 m²) replicated four times. There were three tillage treatments: conventional (mouldboard plough 25-30 cm deep, cultivator, harrow, roller, residue removed), minimum (chisel plough 10 cm, harrow, roller, residue retained), no-till (herbicides, residue retained). Within these were cereal (wheat Triticum aestivum, barley Hordeum vulgare)/legume (vetch Vicia sativa) and cereal/cereal rotations. Samples of cereal grain and straw were taken. Soil samples were taken from each plot (0-30 cm) before and after cropping. Soil density and organic matter were measured.