1. Introduction
Achieving the balance between yield and the preservation of the agro-environment has always been the biggest challenge in agricultural development. Within this context, the debates about the sustainability of conventional and organic farming have never ceased (Avery, 1998; Badgley et al., 2007; Connor, 2008; Pretty & Hine, 2001). This debate is now becoming a critical and urgent issue in the 21st century, as the ever-increasing world population requires higher agricultural yields while the deterioration of the agro-environment is becoming more and more serious due tomodern agriculture's excessive dependence on environmentally detrimental inputs.