Effectiveness of the GAEC standard of cross compliance Crop rotations in maintaining organic matter levels in soils

Our study was conducted in the framework of EFFICOND project, with the aim of evaluating the environmental effectiveness of GAEC (Good Agricultural and Environmental Conditions) standards with particular focus to the maintenance of soil organic matter (SOM) levels through the appropriate crop rotation. The study analyzed the effect of crop rotation on the build-up of soil organic matter in three different areas of Italy, located in the North (Lodi), Centre (Fagna, Firenze) and South (Foggia) of Italy, characterized by different climate, soil, and cropping systems. In the two experiments conducted in the South of Italy, in a dry Mediterranean climate, the stock of C was kept steady in most of the rotations compared with the monoculture of durum wheat. In such environment, with very dry and hot summers, introducing a year of fallow seems to improve SOM content, but these data need further investigation. In the Centre of Italy (Fagna), with less extreme climate than in Foggia, the effect of rotation compared to the monoculture of maize is negligible, but investigation on the soil organic matter composition, showed that in the rotation the SOM appeared to be more stable and, in the long term, probably more resistant to degradation. Eventually, experiments conducted in the North of Italy, showed that the monoculture, despite the application of FYM (Farm Yard Manure) or semi-liquid manure, led to a decrease of SOM. To an increase of the rotation complexity, corresponded an increase in the stock of C in soil. Summarizing, results showed that crop rotation could guarantee the maintenance of SOM level, given that the input of C to the soil is maintained at a good level or, in other word, that productivity of the system is high. Other practices such as conservation tillage, appropriate management of residues, and manure application could enhance the positive effect of rotations. Moreover, preliminary investigation of soil microbial diversity, suggests the positive effect of rotations on soil biological fertility.