|Authors: ||G. Bongi, S. Salatino, J. Morábito, J. Amorena, J. Cólica, J. León|
|Keywords: ||Juglans regia cv. Chandler, walnut rootstocks, root conductivity, root density|
In semi-arid conditions it is essential for irrigation economy to gather information about the topology of secondary root architecture.
This experiment started with J. regia cv.
Chandler 12 y-old plantation on different rootstocks, with the same flood irrigation.
Trunk diameters were all in the range 45-60 cm and 15% of the orchard ground was free of shadow at noon; all trees had similar aspect and good fruit production.
The exploited soil radius (Landsberg and Mcmurtrie, 1984) was 4.4 m for Paradox, 5.2 m for J. hindsii and 6.7m for J. regia. A similar tree structure above ground, characterized by similar fruit production and leaf density, corresponded to different root densities profiles and led to different water absorption strategies using rootstock of different origin.
The species of riparian origin had shorter and less dense root densities after 12 years of growth.
Hydraulic conductivity of root sections varied according to size, but within a size, according to rootstock species. Juglans regia had got conductivity an order of magnitude lesser than Paradox and J. hindsii, at about 5–10 m2. For any given water demand of the crown leaves, root expansion rate was regulated to sustain it by an automatic balance with root sapwood effective area.
In this experience root growth appears regulated from aerial part, from top to bottom.
The aerial part determines the conducting root dimension according to root conductivity.
Higher root conductivity corresponded to smaller root systems. J. regia rootstock seems to be adapted to slower and wider water supplies than riparian rootstocks.
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