Can olive growing mitigate the greenhouse effect? A study of carbon cycle from atmosphere to olive tree products

Olive tree is one of the most typical and economically important species belonging to the Mediterranean area but the role of olive orchards and the involvement of different cultivation techniques on atmospheric CO2 fixation is still not completely known. Values of fixed atmospheric CO2 and CO2 accumulation rates were calculated by the increments of dry matter measured at the end of vegetative season in a young olive orchard during a period of seven years from the planting. The same measurements were done on a mature olive orchard, in order to find correlations between the rate of CO2 fixation and the age of plants. In young orchard, fixed CO2 has been allotted mainly in wood, while the rest in leaves and fruits. Movements of fixed carbon in pruning material and senescent leaves, and their contribuition in soil organic carbon increase and in humus production were studied both in young and mature orchards. The number of plants per hectare and the use of appropriate agricultural practices (pruning, green manure, irrigation management), as well as local pedoclimatic characteristics, had a fundamental importance in trasforming a significant part of CO2 in humus and biomass. The results obtained underline the important role of olive orchards in mitigating the damage caused by greenhouse effect and highlight the positive role of olive growing in the fixation of atmospheric CO2, in particular during the formation of the permanent structure of olive plants.