TITLE:
Growth of Young Olive Trees: Water Requirements in Relation to Canopy and Root Development
AUTHORS:
Masmoudi-Charfi Chiraz
KEYWORDS:
Growth Pattern; Phenological Stage; Olive Variety; Competition; Root Density; Root-Canopy Ratio; Irrigation Management
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.4 No.7,
July
5,
2013
ABSTRACT: The study was carried out in northTunisia(36.5?N, 10.2?E) in order to get a comprehensive view of the growth dynamic of young olive orchards (Olea europaea L.,). The experiment
involved irrigated trees of cultivars Chétoui, Manzanille, Meski and Picholine, planted
at 6 ×6 m2spacing. Tree height, shoot length and canopy, fruit and trunk diameters were monitored regularly after plantation on 12 trees per variety.
Root development was analyzed on Chétoui trees, only. Growth patterns were
established annually for each variety before proposing an average model for
each growth parameter. Results showed that tree height, shoot length and trunk
diameter grew following an S-shaped curve with maximum annual increases
occurring on the 4th year for tree height and a year later for
canopy. The minimum gain coincided
with the highest fruit load year, indicating that competition for assimilates concerns
also young trees. Average growth patterns for tree
height and shoots showed
sustained rates all over the growing season with seven distinct periods of growth. Rapid
growth occurred in April, July, and September, with similar growth trends
observed for productive and less productive cultivars. However, the studied
varieties behaved differently. Picholine cv., provided the most important increases and was the best
water user. Results also showed that most roots were confined to the top soil
layers and developed nearby the trunks. High root densities and important water
depletion were observed in this area and thus, water and fertilizers should be
supplied for young trees at these depths and distances from trunks. Root and
canopy development were
highly correlated (r = 0.94) and
interfered with fruit growth. When trees set their first productions, the root-canopy ratio
approximated the unit. An optimum ratio between root length and
leaf area was found (2.3 km·m?2) for the
6-year-old tree, indicating good equilibrium between the above and the underground parts. On the basis of
these results, a mathematical model was developed allowing a precise estimation
of water requirements of olive trees during a period, where ground cover rarely
exceeds 30%. We can conclude that all these models, graphic and mathematic give
precise information on the occurrence of the various phenophases of young olive
trees and may be used for a quantitative appraisal of the performance of olive varieties under a given
environment. However, some aspects would be probed deeper and particularly the influence of
climatic data on growth dynamic.