CONICET | Buscador de Institutos y Recursos Humanos

Although a number of studies have evaluated many aboveground aspects of olive production, essential root system characteristics have been little examined. We assessed the seasonal pattern of both shoot elongation and root growth in three commercial orchards under drip irrigation near Aimogasta, La Rioja (northwestern Argentina) over three years. Three rhizotrons were installed 60 cm from the drip line in each Manzanilla orchard in September 2003. The trees were 5-7 years old at the beginning of the study depending on the orchard. Root length and number was monitored every 6-8 weeks until February 2006 by tracing roots onto clear plastic film, digitizing the tracings in the laboratory, and analyzing the images with readily available root length software. With some exceptions, peaks in stem elongation and root length occurred during the spring with a secondary peak in the fall. The root growth peak preceded the stem elongation peak in the spring, but followed the shoot peak in the fall. Despite high levels of irrigation, little growth in either stems or roots occurred during the summer possibly due to competition for carbon assimilates and nutrients during the rapid growth phases of the fruits or due to high air temperatures. The most pronounced difference in growth between the stems and roots occurred during the winter when the roots maintained up to 40% of maximum growth rates, but the elongation of stems was minimal. These results may have important implications for fertilization and irrigation strategies in the new intensively managed olive plantations in northwestern Argentina.