Effect of different crop management systems on rainfed durum wheat greenhouse gas emissions and carbon footprint under Mediterranean conditions

The impact of management practices and input intensities on the greenhouse gas (GHG) emissions and carbon footprint (CF) of Italian durum wheat is not well documented. A field experiment was established in 2009 to gain insight into the effects of different crop management systems on total GHG emissions of faba bean–wheat rotations per unit area over five years. The aim was to estimate the emission intensity generated from the production of 1 kg of durum wheat in a typical wheat cultivation area of southern Italy. We proposed different crop management systems to reduce GHG emissions and enhance crop productivity. The proposed management practices consisted of three levels of soil disturbance – conventional (CT), reduced (RT) and no-tillage (NT) – and different nitrogen (N) fertilizer rates. These were applied and tested in order to validate their workability in the area. Results showed relatively higher emissions resulting from the pre-farm phase, whereas the cultivation phase was responsible for 49%, most of which was due to soil emissions (37.4%). In average, our wheat system was responsible for the emission of 1481.1 kg CO2eq ha−1 and 0.295 kg CO2eq Kg−1 of grain, which varied significantly between the proposed management systems. The tillage system had a significant impact on the total emissions. In general, NT and RT resulted in lower emissions than CT, although there were some exceptions in terms of GHG emissions per kilogram of grain due to the lower productivity of RT compared to CT and NT. On a hectare basis, NT reduced the emissions by 22% and by 35% on a kilogram basis compared to the highest emissions in CT in RT, respectively. N fertilizer, however, had both strong direct and indirect effects on total emissions resulted in increase by 60% when the highest N rate was applied. This positive correlation was reflected in CF data where a minimum of 0.155 kg CO2eq kg−1 of grain was obtained when the lowest N fertilizer rate was applied with a reduction of 65%. This was very much linked to the grain yield, thus, a low grain yield together with a high N fertilizer rate led to higher emissions and, therefore, a higher carbon footprint. The effect of the cropping system was clear, as the grain yield increased compared to the base year, with a consequent 31% reduction in CF at the end of the study period. This is the first study in Italy to focus on the emission intensities associated with the production of durum wheat using different input intensities. Our findings indicate that achieving synchrony between minimum input requirements and crop demand without excess or deficiency is the key for optimizing a trade-off between yield and environmental protection.