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