Carbon sequestration of hazelnut orchards in central Italy

Abstract

The cultivation of European hazelnut (Corylus avellana L.) is showing a rapid increase due to the high global demand for hazelnuts from the confectionery industry also affecting Italy, which is the second largest hazelnut producing country after Turkey. Like most tree crops, hazelnut tree planting includes land preparation and frequent tillage operations during the first years of growing seasons to avoid weed competition, whereas after 3 years the soils are usually permanently grass covered. The aim of this work is to develop a model of carbon sequestration based on the age of hazelnut orchards, using permanent grasslands as reference for previous land use. The results demonstrate that soil carbon stock (sCS30) tends to decrease between 23% and 58% during the first 3–5 years after cultivation. This carbon depletion is only partially compensated by the carbon sequestration of the hazelnut trees, variable from about 0.6–3.3 Mg C ha−1. Adult hazelnut orchards showed high levels of sCS30, as well as higher carbon stock (CS) from tree biomass, resulting in similar, or even higher carbon sequestration potential of the grassland. In some cases, excessive nitrogen fertilization seems to decrease the carbon sequestration potential of the soil. In conclusion, the land use change from grassland to hazelnut cultivation has a short-term negative impact in terms of soil carbon sequestration. In orchards with optimal fertilization and management, sCS30 is recovered and exponentially increased, highlighting the high carbon sequestration potential offered by this kind of perennial nut crop.