Potential of Carbon Accumulation in No-Till Soils with Intensive Use and Cover Crops in Southern Brazil

• Published in: Journal of environmental quality 2006-07, Vol.35 (4), p.1599-1607
• Main Authors: Amado, T.J.C, Bayer, C, Conceicao, P.C, Spagnollo, E, Campos, B.H.C. de, Veiga, M. da
• Format: Article
• Language: English
• Subjects: Accumulation; Agricultural practices; agricultural soils; Agriculture - economics; Agriculture - methods; Agronomy. Soil science and plant productions; Applied sciences; Biological and medical sciences; Biotechnology; Brazil; Cajanus cajan; carbon; Carbon - analysis; Carbon - metabolism; Carbon dioxide; carbon sequestration; Cereal crops; Clay loam; Conferences; conventional tillage; Corn; Cover crops; crop rotation; Cropping systems; Crops, Agricultural - growth & development; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environment and pollution; Environmental Monitoring; Exact sciences and technology; Experiments; Farmers; Farmworkers; Fossil Fuels - economics; Fundamental and applied biological sciences. Psychology; Gases - metabolism; Glycine max; Greenhouse Effect; Industrial applications and implications. Economical aspects; lability; Loam soils; long term experiments; Medical treatment; no-tillage; Nonfiction; Organic Chemicals - analysis; Organic Chemicals - metabolism; Organic matter; Oryza sativa; Particulate organic carbon; Phaseolus vulgaris; Piper; Pollution; Pollution, environment geology; Soil - analysis; Soil aggregates; Soil organic matter; Soil texture; Soils; Sorghum bicolor; Soybeans; subtropical soils; Time Factors; Triticum aestivum; Winter; Zea mays; Zea mays - growth & development
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq2005.0233

The area under no-till (NT) in Brazil reached 22 million ha in 2004-2005, of which approximately 45% was located in the southern states. From the 1970s to the mid-1980s, this region was a source of carbon dioxide to the atmosphere due to decrease of soil carbon (C) stocks and high consumption of fuel by intensive tillage. Since then, NT has partially restored the soil C lost and reduced the consumption of fossil fuels. To assess the potential of C accumulation in NT soils, four long-term experiments (7-19 yr) in subtropical soils (Paleudult, Paleudalf, and Hapludox) varying in soil texture (87-760 g kg-1 of clay) in agroecologic southern Brazil zones (central region, northwest basaltic plateau in Rio Grande Sul, and west basaltic plateau in Santa Catarina) and with different cropping systems (soybean and maize) were investigated. The lability of soil organic matter (SOM) was calculated as the ratio of total organic carbon (TOC) to particulate organic carbon (POC), and the role of physical protection on stability of SOM was evaluated. In general, TOC and POC stocks in native grass correlated closely with clay content. Conversely, there was no clear effect of soil texture on C accumulation rates in NT soils, which ranged from 0.12 to 0.59 Mg ha-1 yr-1. The C accumulation was higher in NT than in conventional-till (CT) soils. The legume cover crops pigeon pea [Cajanus cajan (L.) Millsp] and velvet beans (Stizolobium cinereum Piper & Tracy) in NT maize cropping systems had the highest C accumulation rates (0.38-0.59 Mg ha-1 yr-1). The intensive cropping systems also were effective in increasing the C accumulation rates in NT soils (0.25-0.34 Mg ha-1 yr-1) when compared to the double-crop system used by farmers. These results stress the role of N fixation in improving the tropical and subtropical cropping systems. The physical protection of SOM within soil aggregates was an important mechanism of C accumulation in the sandy clay loam Paleudult under NT. The cropping system and NT effects on C stocks were attributed to an increase in the lability of SOM, as evidenced by the higher POC to TOC ratio, which is very important to C and energy flux through the soil.