A simplified method for the assessment of carbon balance in agriculture: an application in organic and conventional micro-agroecosystems in a long-term experiment in Tuscany, Italy

Summary

Many research works propose sophisticated methods to analyse the carbon balance, while only a few tools are available for the calculation of both greenhouse gas emissions and carbon sequestration with simplified methods. This paper describes a carbon balance assessment conducted at farm level with a simplified methodology, which includes calculations of both CO2 emissions and carbon sequestration in crop rotations. This carbon balance was tested in the Montepaldi Long Term Experiment (MOLTE) trial in central Italy, where two agroecosystems managed with two different farming practices (organic vs conventional) are compared. Both in terms of CO(2)eq emissions and carbon sequestration, this simplified method applied in our experiment provided comparable results to those yielded by complex methodologies reported in the literature. With regard to the crop rotation scheme applied in the reference period (2003-2007), CO2 emissions from various farm inputs were found to be significantly lower (0.74 Mg ha(-1)) in the organically managed system than in the conventionally managed system (1.76 Mg ha(-1)). The same trend was observed in terms of CO(2)eq per unit of product (0.30 Mg kg(-1) in the organic system and 0.78 Mg kg(-1) in the conventional system). In the conventional system the sources that contributed most to total emissions were direct and indirect emissions associated with the use of fertilisers and diesel fuel. Also the stock of sequestered carbon was significantly higher in the organic system (27.9 Mg ha(-1) of C) than in the conventional system (24.5 Mg ha(-1) of C). The carbon sequestration rate did not show any significant difference between the two systems. It will be necessary to test further this methodology also in commercial farms and to validate the indicators to monitor carbon fluxes at farm level.