Soil fertility remediation in fruit tree orchards in Mediterranean areas

In recent decades intensive agricultural practices (continual tillage, use of mineral fertilisers, use of low-quality irrigation water and removal of pruning waste) as combined with Mediterranean climate characteristics (i.e. low precipitation, high summer temperatures) have dramatically degraded cultivated soil, reducing soil organic carbon (SOC) to about 1%. Such poor condition negatively affects a large number of soil characteristics being unfavourable for plant physiology and thus for achievement of high fruit quality. Particularly, soil hydrological properties are impaired and soil waterholding capacity reduced. Increase water stored into soil by increased SOC may represents a key factor to face with recurrently water shortage in the Mediterranean-typeclimates. Therefore, the aim of the present study was to explore effects of different agricultural management practice on SOC content. We report carbon stored into soil by peach and kiwifruit orchards obtained by accurately monitoring CO2 fluxes between orchards and atmosphere. Results show that a sustainable soil management (cover crop, no-tillage, compost application, mulching of pruning residues, regulated deficit irrigation) determines a net CO2 fluxes to be negative (about -17 t ha−1 year−1) because emissions are lower than stored CO2 increasing SOC. While in a conventionally managed orchard such a flux was positive (about + 6 t ha−1 year−1) continuing to impoverish SOC. Potential role of soil fertility remediation through increasing its carbon content to sequester atmospheric CO2 is also discussed.