Root topography in high-density olive orchards

Root distribution and growth in high-density olive orchards require more detailed investigation. Proper root development can promote vegetative growth during the early years after planting and postpone physiological ageing in adult olive groves. The topography of the root was evaluated in the ‘Maurino’ cultivar in 2- and 10-year-old high-density olive orchards (4×2 m, 1,250 trees ha-1), located in Rome and Ancona (central Italy), respectively. Soil samples were taken at predetermined distances and depths on 8 trees of similar size in each orchard. The soil samples were dried, weighed and the olive roots were separated using a sieve and then scanned. Images were processed with WinRHIZO™ software to obtain the total root length, the mean root diameter and the root length density (RLD). In the young olive orchard, roots had larger diameter in the most superficial layers of soil and in the areas closest to the stem, while the RLD was greater in the first centimetres of soil along the row. Root also explored the inter-row without limitations due to the presence of the natural mulching. In the adult orchard, the results were consistent with those of the young one even though the root density was minimal at about 1-m distance between the trees along the row and the diameter of the roots was very small in the area of the inter-row subjected to compression by the passage of the machines. In conclusion, in the considered high-density orchards, the root system grew both along the row and in the inter-row. In adult trees, limitations to the root development may be due to autopathic phenomena between contiguous olive trees along the row or by portions of soil subjected to excessive compaction due to the periodical passage of machines in the inter-row.