Soil management affects carbon dynamics and yield in a Mediterranean peach orchard

A field trial was conducted over a seven-year period, in Mediterranean peach orchard. The aims were (i) to explore the effects of alternative soil-management practices (Amng) on soil and litter carbon (C) reserves, (ii) to monitor the seasonal and (iii) spatial variations of soil CO2 flushes. The alternative management included no tillage, retention of all aboveground biomass and application of imported organic amendments (15 t ha−1 y−1 fresh weigh). Locally conventional management (Lmng) served as the control: i.e. tillage, mineral fertilisation, removal of prunings. The mean total annual C inputs were 4.2 and 2.4 t ha−1 in Amng and Lmng, respectively. Spatial and temporal variations in CO2 soil emissions over a 20 m2 plot (×2) were assessed (Li-6400, LI-COR, USA) on the assumption that root topography and microbial activity declined systematically with distance from the row line. Under Amng practices soil C significantly increased up to 1.78% against 1.38% at Lmng block. The C stored as litter and dead wood in Amng, was 16-times that in Lmng. On a whole-season basis, CO2 losses were 20% higher in Amng than in Lmng. 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. It is concluded that despite a higher CO2 soil emissions, alternative management techniques will partially offset atmospheric CO2 rise through increased soil C reserves, and that spatial variability of emissions must be taken into account if the accuracy of estimates of large-scale emissions are to be improved.