Forages, cover crops and related shoot and root additions in no-till rotations to C sequestration in a subtropical Ferralsol

• Published in: Soil & tillage research 2011-01, Vol.111 (2), p.208-218
• Main Authors: Santos, Nícolas Zendonadi dos, Dieckow, Jeferson, Bayer, Cimélio, Molin, Rudimar, Favaretto, Nerilde, Pauletti, Volnei, Piva, Jonatas Thiago
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Carbon saturation; carbon saturation level; carbon sequestration; Chemical, physicochemical, biochemical and biological properties; corn; cover crops; crop residues; crop rotation; Crop-livestock; forage crops; Fundamental and applied biological sciences. Psychology; Glycine max; intercropping; Legumes; no-tillage; Organic matter; Physical fractions; Physics, chemistry, biochemistry and biology of agricultural and forest soils; roots; shoots; soil organic carbon; Soil science; Southern Brazil; soybeans; subtropical soils; Triticum aestivum; winter wheat; Zea mays
• ISSN: 0167-1987; 1879-3444
• DOI: 10.1016/j.still.2010.10.006

▶ Forage-based contribute more to soil C sequestration than cover crop-based rotations. ▶ Legume contributes more than grass cover crop to soil C accumulation in no-tillage. ▶ Soil C accumulation relates better with root than with shoot additions. ▶ Most of C accumulation in crop rotations occurs in the mineral-associated fraction. ▶ There is a trend for C saturation due to root additions in no-till soil. To improve C sequestration in no-till soils requires further development of crop rotations with high phytomass-C additions. The objectives of this study were (i) to assess long-term (17 years) contributions of cover crop- or forage-based no-till rotations and their related shoot and root additions to the accumulation of C in bulk and in physical fractions of a subtropical Ferralsol (20-cm depth); and (ii) infer if these rotations promote C sequestration and reach an eventual C saturation level in the soil. A wheat (Triticum aestivum L., winter crop)–soybean (Glycine max (L.) Merr, summer crop) succession was the baseline system. The soil under alfalfa (Medicago sativa L., hay forage) intercropped every three years with maize (Zea mays L., summer crop) had the highest C accumulation (0.44MgCha−1year−1). The bi-annual rotation of ryegrass (Lolium multiflorum Lam., hay winter forage)–maize–ryegrass–soybean had a soil C sequestration of 0.32MgCha−1year−1. Among the two bi-annual cover crop-based rotations, the vetch (Vicia villosa Roth, winter cover crop)–maize–wheat–soybean rotation added 7.58MgCha−1year−1 as shoot plus root and sequestered 0.28MgCha−1year−1. The counterpart grass-based rotation of oat (Avena strigosa Schreb., winter cover crop)–maize–wheat–soybean sequestered only 0.16MgCha−1year−1, although adding 13% more C (8.56Mgha−1year−1). The vetch legume-based rotation, with a relative conversion factor (RCF) of 0.147, was more efficient in converting biomass C into sequestered soil C than oat grass-based rotation (RCF=0.057). Soil C stocks showed a close relationship (R2=0.72–0.98, P