CO2 sequestration from Italian cultivated land: opportunities, challemnges and risks

Management of agricultural soils may determine soil carbon emission to the atmosphere (source) or soil carbon sequestration (sink). Conventional agriculture is tillage-based (TA) in industrialised as well as developing countries and relies, as a key procedure for seedbed preparation, on mechanical soil tillage with no organic mulch cover. Generally, it seems to speed up the loss of Soil Organic Matter (SOM), by increasing its mineralization and through soil loss by erosion. In addition, soil tillage is a high energy-consuming operation that uses large amounts of fossil fuel per hectare in mechanised systems. In contrast to tillage-based systems, Conservation Agriculture (CA) is considered to be an agro-ecological approach to resource-conserving agricultural production that requires compliance with three linked practical principles, namely: i) minimum mechanical soil disturbance (with no-till and direct seeding); ii) maintenance of permanent organic soil cover (with crops, cover crops and/or crop residues); and iii) species diversification through crop rotations and associations (involving annual and/or perennial crops including tree and pasture crops) Corsi et al. (2012). CA facilitates good agronomy, such as timely operations, and improves overall land husbandry for rained and irrigated production and is complemented by other good practices, such as the use of quality seeds and integrated pest management (Pisante et al., 2012).There is evidence that, in the medium term, the most effective way for adaptation to climate change is represented by a rational management of the biosphere and in particular of the agricultural sector: by the adoption of specific agricultural practices. Agriculture is potentially able to reduce its emission with minor costs with respect to other activities, to increase carbon sequestration and reduce greenhouse gas emissions. In fact, agricultural activities play a fundamental role in soil carbon sequestration and reduction of emissions, mainly because of the high stock capacity of this element associated with long retention time in the soil. The cultivated land (arable and tree crops) occupy 28% of the Italian territory, for a total of 10.9 million ha which can stock massive reserves of carbon by putting in place agronomic measures and/or agro-ecological infrastructure useful to reduce the amount of CO2 in the atmosphere. The net balance of the two processes on an annual basis can result in positive net flows (emissions) or negative (sequestration). However, the aggregated balance sheet of carbon for agricultural soils is subject to significant uncertainties with estimates that can vary greatly depending on the method and data sources. The average European values, for example, range from losses of -0.17 ± 0.33 Mg C ha-1 y-1 (emissions), when calculated from data in the inventory of agricultural soils (available for 33% of the European cultivated land) to values of accumulation of 0.15 ± 0.15, or loss of -0.08 Mg C ha-1 y-1 when calculated with simulation models. It is estimated that in Italy over the past 70 years, the intensification of agricultural activities has caused a net loss of soil organic carbon by 39% compared to the initial content. The extent of actual SOC sequestration achieved on Italian cultivated land will crucially depend on future policies which could contemplate the inclusion of agriculture in an emissions trading scheme, either as a covered sector, or as an offset provider. It is important to face some research questions mainly aimed at removing this barrier to inclusion of soil carbon in emissions trading. Complementary measures, such as research, development and technology transfer to improve the extension to improve adoption of existing techniques or direct financing to accelerate the adoption of conservation farming systems, should be carried out.