The influence of soil water regime on the root system growth of young olive tree

Minirhizotrons were used to observe, throughout the annual cycle, the root length density (RLD, cm cm-3) of fine roots in young olive trees (Olea europaea L., cv. Coratina) grown in irrigated and rainfed conditions. The trial was carried out in a semi-arid Mediterranean environment of Southern Italy. The root length density at different depths and distances from the trunk was examined during winter rest, flowering, and pit hardening. Results proved that RLD of irrigated trees was always higher than that shown by the non-irrigated ones, except at the end of July, when heavy rainfall wetted the soil surface layers stimulating root activity in the rainfed plants. Irrigated trees, differently from plants grown under rainfed conditions, showed a root density peak during the winter rest. Root growth pattern was also affected by the sink-source competition occurring throughout the annual season.