Spatial and temporal variability of CO2 soil emission in a Mediterranean peach orchard

Loss of soil carbon from cultivated land contributes both to soil degradation and global warming. In agroecosystems CO2 emissions related to fossil fuel energy use are roughly well established, whilst little is know concerning the soil CO2 emissions at orchards, this hampers development of adequate and environmental friendly policies and orchard management strategies. Therefore, a field trial was conducted in Mediterranean peach orchard in order to explore the seasonal and spatial variations of soil CO2 flushes. The orchard was managed according to locally conventional practices (i.e. tillage, mineral fertilisation, removal of prunings, drip irrigation). Spatial and temporal variations in CO2 soil emissions over a 20 m2 plot were assessed (LiCor 6400) midday at a 10-15 interval time from January to December. Sampling points (×30) were located at different distances from row line. Soil temperature and moisture were simultaneously assessed. A clear pattern of CO2 emission rate was detected showing it was at the minimum values of approx. 0.02 mol m-2 s-1 (Jan/Dec) and peaked at 0.2 mol m-2 s-1 (end of May) just before the warmer months. Soil CO2 emissions were mostly from the in-row, with the inter-row emissions being lower, especially due to reduced soil-water content during the drier months. We concluded that spatial variability of emissions must be take into account if the accuracy of estimates of large-scale emissions are to be improved. Moreover, the need to include CO2 soil emissions when some CO2-related parameters (e.g. carbon footprint) are computed is discussed.