Conference Paper

Soil Carbon Stocks, Carbon Dioxide Sequestration and Tillage Techniques

Conference: 10th Congress of the European Society for Agronomy
Source: OAI

ABSTRACT C sequestration via agricultural soils can be accounted for, under Article 3.4 of the Kyoto Protocol, provided that specific measures are implemented.
Sound cropland management can play a positive role in reducing GHGs emissions, and carbon dioxide in particular, through a decrease of soil organic matter (SOM) and soil organic carbon (SOC) losses, by increasing the carbon input or combining these two options. Literature data estimate about 1.500 Pg SOC (1 Pg = 1015 g) to 1 m depth, in comparison with 4.000 Pg C of fossil fuels, indicating SOC as the largest sink of C after fossil fuels. Vegetation (600 Pg) and atmosphere (760 Pg) store considerably less C than soils.
Carbon sequestration can occur through a reduction in soil disturbance, since more carbon is lost as CO2 from tilled soils in comparison with reduced or sod-seeding systems. Scientific results show that no tillage systems could absorb on average 0.7-1.4 t CO2 ha-1 yr-1.
This paper compares the long-term effects of conventional tillage and sod-seeding on SOC, in a two-years rotation field plot system (durum wheat-sunflower 1994-2001; durum wheat-corn 2002-2006). The experiment was established in 1994 at the farm “P. Rosati” of the University of Ancona in Agugliano, a hilly area with a silty-clay soil. A split-plot randomized block design was set-up. We report in this paper results from two tillage techniques (C: conventional, i.e. ploughing at 40 cm depth; S: sod-seeding) and two nitrogen fertilization rates (0-90 kg N ha-1). SOC was determined in 2006 after 12 years of continuous ploughing vs. sod-seeding on 16 soil profiles.
The amount of organic C and the equivalent CO2 in t ha-1 were calculated for individual soil profiles at three depth intervals: 0-30, 30-50 and 50-100 cm. Differences among treatments were not significant, although a decreasing trend in CO2 sequestration in top soil, from sod-seeding to conventional tillage (SN90>SN0>CN90>CN0) was likely.
The availability of previous SOC determinations on four of the sixteen profiles allowed comparing SN90 and CN90 plots after a period of ten years (1996-2006). Results showed an increase of soil carbon stocks and CO2 sequestration in the no tilled plots, and a decrease in the conventional system.

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May 15, 2014

Rosa Francaviglia