Can Organic Farming Contribute to Carbon Sequestration? A Survey in a Pear Orchard in Emilia-Romagna Region, Italy

The effect of organic fertilisation on the level of total organic carbon (TOC) in an 18-years old pear orchard (cv. Abate Fetel) was evaluated vs. a conventional pear orchard mineral fertilized (control). In both orchards soil samples (Typic Udochrept loamy soil) were taken at two depths (0-15 and 30-50 cm) along the row (tilled and mainly amended with compost) and in the inter-row space (grassed with different Graminaceae species in the organic orchard, bare in the conventional orchard). The area (elevation 20 m), located in Bologna province, Emilia-Romagna Region (Italy), is characterised by mean annual temperature 13.1 °C and rainfall around 750 mm. In the horizon 0-15 cm of the row an increase of about 14 tons ha-1 of TOC has been calculated after 18-years of cultivation and amendment compared to the control soil, which had received just mineral fertilisation. A significant increase of TOC (about 6.3 tons ha-1) was also measured in the top layer (0-15 cm) in the grassed inter-row, where this C sink is exclusively due to the cover crop. A survey of the role of organic vs. conventional farming on soil C sink/source is started in 2007 in 8 typical organic orchard farms located in Emilia-Romagna Region and it is still running.