Sustainable orchards as an atmospheric CO2 offset tool

Agriculture is responsible for almost 14% of equivalent CO2 emissions, but it has a potential role in mitigating climate changes, with the identification of alternative management practices aimed to reduce CO2 emissions and increase CO2 capture. Climate changes (mainly increased temperature and precipitation changes) will have agricultural consequences due to the interrelations between climate and soil degradation, land and water use. This paper reports results on the effects of changed soil management practices from conventional (soil tillage, mineral fertilisers, burning of pruning residues) to sustainable (no-tillage, pruning residues and cover crop retention, compost application) on carbon pools. Results show that a 7-year period of changed practices (including carbon input at a mean rate of 8-9 t/ha C per year) significantly increased SOC concentration (from 1.3% up to 1.8%, upper 0.1 m) and carbon litter. Considering the various carbon pools, it has been preliminary estimated that approx. 50 t/ha CO2 were stored (0.4 m soil depth) at the end of the experimental period at the sustainable plot. By contrast, the conventional plot continued to be a CO2 source mainly because of tillage and burning of prunings. The paper shows the beneficial effects of sustainable practices on yield which was improved by 30-50% as compared with conventional managed orchards. The effects of carbon addition on reserves of soil nutrients (N, P, K, Ca, Mg) and on CO2 soil emission are discussed.