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R.M. Crassweller and D.E. Smith

A peach and nectarine cultivar and training trial was planted in 1989. Training methods were open center (OC) and central leader (CL). The orchard was divided into three sections for early, mid-, and late season peaches with 10 individual-tree replications. The following characteristics were measured from 1989 to 1994: trunk cross sectional area, fruit yield, number of fruit, and fruit color. Early season peaches, those ripening with and before `Salem' in the OC system had significantly greater TCSA at the end of the fifth growing season. At the end of the sixth growing season, however, there was a significant training cultivar interaction. There were no differences between the mid- or late season cultivars. Measurable yields were obtained in 1991 through 1993. In all years, greater yields per tree were observed from trees in the CL system, although not significantly different for the late season cultivars. `Redhaven' and `Newhaven' had the highest yields for the early season cultivars, `Glohaven' for the mid-season cultivars, and `Cresthaven' and Biscoe for the late season cultivars. Trees in the CL system tended to have higher tree efficiency than trees in the OC system. Fruit color at harvest varied by year and training system.

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Esmaeil Fallahi and D. Ross Rodney

The influence of six rootstock on growth, yield, fruit quality, and leaf mineral nutrient concentration of `Fairchild' mandarin [`Clementine' mandarin (Citrus reticulata Blanco) × `Orlando' tangelo (C. paradisi Macf. × C. reticulata)] is reported for the arid climate of southwestern Arizona. Trees on macrophylla (Alemow) (C. macrophylla Wester) were precocious and produced high yield 4 years after planting. Six-year cumulative yields of trees on Volkamer lemon (C. limon Burro f.), Carrizo citrange [C. sinensis (L.) Osbeck × Poncirus trifoliata (L.) Raf.], Taiwanica (C. taiwanica Tan. & shin.), and rough lemon (C. jambhiri Lush.) were similar and higher than those of trees on macrophylla and Batangas mandarin (C. reticulata). `Fairchild' mandarin tree canopies were large with Volkamer lemon and Taiwanica; intermediate with Carrizo citrange, rough lemon, and Batangas mandarin; and small with macrophylla rootstock. Fruit from trees on Carrizo citrange had the highest soluble solids concentration (SSC), while those on Volkamer lemon and rough lemon had the lowest SSC and total acids. `Fairchild' trees on macrophylla had higher levels of leaf N, Mn, and Fe but lower Ca, while trees on Batangas mandarin and Carrizo citrange had higher leaf K than those on the other rootstock. Trees on Volkamer lemon had higher leaf Zn than those on Carrizo citrange, Taiwanica, rough lemon, and Batangas mandarin rootstock. Considering yield, growth, fruit quality, and/or leaf nutrient concentration, Volkamer lemon, Carrizo citrange, Taiwanica, and rough lemon are suitable for `Fairchild' mandarin in the arid regions of southwestern Arizona. Trees on macrophylla could be advantageous for short-term planting, but would not be satisfactory for long-term planting because of gradual decline in growth and yields. Batangas mandarin is not recommended for `Fairchild' mandarin due to poor production.

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John E. Fucik

To meet the Federal Crop Insurance's need to estimate the fruit crop on young citrus trees with no bearing history and partial fruit loss, the relationships between tree age, trunk and canopy size, and yields were studied. Pertinent data taken over many years from 1- to 7-year-old trees were analyzed using SAS regression procedures. The correlations for tree age × trunk diameter and truck diameter × canopy size were highly significant with R2 > 0.80. Although its R2 was only 0.20, the canopy size × yield correlation provided an acceptable estimate of the potential yields of grapefruit trees ≤6 years of age. The effect of 20% to 80% leaf loss on subsequent yields was determined in a field experiment, and the results included with a training guide on estimating leaf loss. The whole program was designed to provide a method by which insurance adjusters with little previous citrus experience could estimate postfreeze yield losses.

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T.A. Wheaton, J.D. Whitney, W.S. Castle, R.P. Muraro, H.W. Browning, and D.P.H. Tucker

A factorial experiment begun in 1980 included `Hamlin' and `Valencia' sweet-orange scions [Citrus sinensis (L.) Osb.], and Milam lemon (C. jambhiri Lush) and Rusk citrange [C. sinensis × Poncirus trifoliata (L.) Raf.] rootstocks, tree topping heights of 3.7 and 5.5 m, between-row spacings of 4.5 and 6.0 m, and in-row spacings of 2.5 and 4.5 m. The spacing combinations provided tree densities of 370, 494, 667, and 889 trees ha. Yield increased with increasing tree density during the early years of production. For tree ages 9 to 13 years, however, there was no consistent relationship between yield and tree density. Rusk citrange, a rootstock of moderate vigor, produced smaller trees and better yield, fruit quality, and economic returns than Milam lemon, a vigorous rootstock. After filling their allocated space, yield and fruit quality of trees on Milam rootstock declined with increasing tree density at the lower topping height. Cumulative economic returns at year 13 were not related to tree density.

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Jaume Lordan, Anna Wallis, Poliana Francescatto, and Terence L. Robinson

). Results Tree size. Larger trees were observed with ‘McIntosh’ compared with ‘Honeycrisp’ ( Table 2 ). For both cultivars, the biggest trees of the trial were with CL systems on ‘M.M.111’, which were 200% to 300% larger than the rest of the treatments

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D.A. Devitt, R.L. Morris, and D.S. Neuman

A 2-year study was conducted to quantify the actual evapotranspiration (ETa) of three woody ornamental trees placed under three different leaching fractions (LFs). Argentine mesquite (Prosopis alba Grisebach), desert willow [Chilopsis linearis (Cav.) Sweet var. linearis], and southern live oak (Quercus virginiana Mill.) (nursery seedling selection) were planted as 3.8-, 18.9-, or 56.8-liter container nursery stock outdoors in 190-liter plastic lysimeters in which weekly hydrologic balances were maintained. Weekly storage changes were measured with a portable hoist-load cell apparatus. Irrigations were applied to maintain LFs of +0.25, 0.00, or -0.25 (theoretical) based on the equation irrigation (I) = ETa/(1 - LF). Tree height, trunk diameter, canopy volume, leaf area index, total leaf area (oak only) and dry weight were monitored during the experiment or measured at final harvest. Average yearly ETa was significantly influenced by planting size (oak and willow, P ≤ 0.001) and leaching fraction imposed (P ≤ 0.001). Multiple regressions accounting for the variability in average yearly ETa were comprised of different growth and water management variables depending on the species. LF, trunk diameter, and canopy volume accounted for 92% (P ≤ 0.001) of the variability in the average yearly ETa of oak. Monthly ETa data were also evaluated, with multiple regressions based on data from nonwater-deficit trees, such that LF could be ignored. In the case of desert willow, monthly potential ET and trunk diameter accounted for 88% (P ≤ 0.001) of the variability in the monthly ETa. Results suggest that irrigators could apply water to arid urban landscapes more efficiently if irrigations were scheduled based on such information.

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Edward L. Proebsting, David Ophardt, William E. Howell, Gaylord I. Mink, and Kim D. Patten

Thirty-five `Bing' sweet cherry (Prunus avium L.) clones were collected, primarily from old commercial orchards in central Washington; propagated on P. mahaleb L. rootstock; and their horticultural performance was evaluated. Nine of the 35 clones were not infected with the common pollen-borne ilarviruses prunus necrotic ringspot virus and prune dwarf virus—four of the clones after decades of exposure in commercial orchards. As a group, the nine virus-free clones produced larger trees with earlier fruit maturity and less rain cracking, but softer fruit, than did the 26 infected clones. These data challenge the general assumption that the presence of one or both of these ilarviruses is always detrimental. This assumption has driven development of many valuable virus certification programs and the adoption of virus-free trees as the standard for commercial fruit growing in most states.

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H.K. Wutscher and K.D. Bowman

Twenty-one selections consisting of 13 numbered hybrids, one ornamental, and seven named cultivars were tested as rootstocks for `Valencia' orange, Citrus sinensis L. Osbeck. The test included six, four-tree replications in randomized complete blocks on sandy soil typical of the center of the Florida peninsula. Trees propagated on Vangasay lemon, HRS 812 (Sunki × Benecke trifoliate orange), and HRS 942 (Sunki × Flying Dragon trifoliate orange) produced more fruit than trees on the other 18 rootstocks in the test. Trees on 10 rootstocks, including the widely used commercial rootstocks, Swingle citrumelo and Carrizo citrange, were intermediate in cumulative fruit production. Trees on five rootstocks, including Sun Chu Sha, Gou Tou #1, and Tachibana, had low yields and trees on HRS 939 (Flying Dragon trifoliate orange × Nakorn pummelo) and sour orange #2 were extremely dwarfed and were minimally productive because of tristeza virus disease. Fouryear cumulative fruit production ranged from 52 to 317 kg per tree. Fruit from trees on HRS 954 and HRS 952 (Pearl tangelo × Flying Dragon trifoliate orange) had the highest, and fruit from trees on Vangasay and Gou Tou #1 had the lowest total soluble solids concentration.

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Richard E.C. Layne

Performance of `Redhaven' peach [Prunus persica (L.) Batsch.] propagated on nine experimental Prunus rootstock was evaluated over 8 years beginning in 1984, in a randomized complete-block experiment with 10 replications on a Brookston clay loam soil type near Harrow, Ont. This experiment was part of an interregional NC-140 peach rootstock experiment. Significant rootstock-induced effects were noted for increase in trunk cross-sectional area, cumulative tree height and spread, cumulative number of root suckers, yield, average fruit weight, yield efficiency, winter injury, cold hardiness, and tree survival. None of the clonally propagated rootstock gave satisfactory overall performance. All trees on GF655-2, 80% on GF677, 60% Self-rooted, and 50% on GF1869 were dead by the eighth year. In addition, suckering was a major problem on GF1869 and a moderate problem on GF655-2. `Citation' induced the most scion dwarfing but had the lowest yields and low yield efficiency. When yield, yield efficiency, fruit size, and tree mortality were considered together, the four peach seedling rootstock performed better than the other Prunus rootstocks and were ranked as follows: Siberian C, Halford, Bailey, and Lovell. Of these, the first three could be recommended with the most confidence to commercial growers who grow peaches on fine-textured soils in northern regions.

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Michael W. Smith

require tree removal within an exceedingly short timespan to prevent crowding. Trees in Hinrichs’ (1961) study averaged 0.55 m 2 /tree cross-sectional trunk area; thus, tree size was within the range where approximately a 50% canopy footprint was a