Effect of Citrus Rootstocks on Root Distribution and Leaf Mineral Content of ‘Orlando’ Tangelo Trees1

Abstract

The effect of rootstock on tree size, root distribution and leaf mineral content of ‘Orlando’ tangelos on 11 rootstocks was studied. Pronounced differences in depth of rooting, weight of feeder roots and tree height were detected. Depth of rooting was correlated to tree height, (r = .58, 1970; r = .83, 1971) i.e., the tallest trees had the deepest root systems. Feeder root wt and tree height were not related. The level of leaf N, K, Ca and Mg but not P was related to rootstock, suggesting a differential absorption of mineral nutrients by rootstock. The level of N appeared to be influenced by root distribution. Trees with deep extensive root systems or with a large number of feeder roots near the surface had high leaf N. Leaf K was significantly correlated with depth of rooting, (r = .96, 1970; r = .84, 1971). The results suggested the maximum performance of all rootstocks was not attained under the uniform cultural conditions of this experiment and therefore the need to examine each rootstock under conditions optimum for it.

Soil Water Use and Apparent Root Efficiencies of Citrus Trees on Four Rootstocks1

“…The growth, productivity and leaf water potentials of the trees on rough lemon suggest that they are well-adapted to deep sands (Table 2) (3,11). The rough lemon root systems had relatively efficient roots at many depths in addition to other characteristics discussed previously which explain the success ful use of this rootstock in the 'Ridge' area.…”

“…Trees on 4 rootstocks, rough lemon, sour orange, sweet orange, and 'Rusk' citrange representing the 2 major stocks of Florida and 2 of lesser importance, respectively, were chosen for study. Selection was based on known differences in tree size, fruiting, and root system characteristics (3,11).…”

“…The physical nature of the soil and its textural uniformity assured a reasonably uniform vertical distribution of water. Root distribution data for the same trees used here had been obtained the previous year (3).…”

“…Differences in rootstock adaptability may be attributed to variations in the depth, density, and distribution of the tree root system (7,13) as well as water uptake and transport efficiency (2). Root systems of rootstocks do differ significantly in distri bution (3). Water use patterns of citrus have also provided some evidence that roots are not equally efficient at all soil depths ( 1, 6, 8), i.e., water uptake is not always directly proportional to root quantity; however, there are few comparisons of water extraction with root distribution and these have generally been limited to one rootstock.…”

Performance of ‘Marsh’ Grapefruit and ‘Valencia’ Orange Trees on Eighteen Rootstocks in a Closely Spaced Planting1,2

“…The control of tree size may be achieved by the selection of the proper rootstock. Tree size is routinely influenced by rootstock in field experiments (4,5,8,11,13); however, the search for dwarfing rootstocks which produce trees 3 m or less in height (5), has, so far, been unsuccessful. Therefore, the objec tive of this study was to evaluate, in a closely-spaced planting, 17 rootstocks which had exhibited dwarfing potential in previ ous experiments or were untested new hybrids which had a dwarfish growth habit as seedlings, and rough lemon.…”