Contribution of soil to CO2 balance in industrial oil crops

Abstract The introduction of a oilseed crop, for energy production, in crop rotations typical of Northern Italy is very helpful for mitigating greenhouse effect; CO2 balance for oilseed crops being always positive as stated by Bona et al. (1999). Very little is known on CO2 evolution from cultivated soils. This incertitude is related to the fact that for producing more energy is necessary to increase input levels (tillage, chemicals ...) which very often induce an increase in soil organic matter degradation. On the other side, an extensive management can slowdown soil organic carbon degradation but the quantity of crop residues produced in this case are lower. In this framework it is necessary to find out the most suitable level of crop management for maximizing the CO2 balance. In the present work the results of some simulations carried out with a model of CO2 evolution from soils (DiSOS model – Bona et al., 2003) applied to sunflower and rapeseed for oil production as a function of soil tillage level are reported. The model was used to simulate the soil organic carbon evolution from 400 cultivations of rapeseed and sunflower which came from a survey made in the Veneto Region (Po valley – northern Italy). The CO2 balance showed the relative weight of soil tillage and the amount of crop residues in determining soil carbon budget. The main factor influencing this budget was the amount of crop residues thus underlining the relevance of reaching high yields. The tillage inputs resulted less relevant in this context.