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D.M. Glenn and W.V. Welker

Mature peach trees were grown in six different-sized vegetation-free areas (VFA) (0.36 to 13 m2) with and without stage-III drip irrigation for 6 years. As the VFA increased, so did the trunk cross-sectional area, total yield/tree, large fruit yield/tree, and pruning weight/tree. The application of supplemental irrigation increased yield of large fruit and leaf N percentage in all VFAs. Winter hardiness was not affected by either size of the VFA or irrigation. The yield efficiency of total fruit and large fruit decreased, however, with the increasing size of VFAs. The smaller VFAs resulted in smaller, more-efficient trees. Managing the size of the VFA was an effective, low-cost approach to controlling peach tree size and, when combined with irrigated, high-density production, offers a potential for increased productivity.

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D.M. Glenn, D.L. Peterson and S.S. Miller

This study evaluated the total and marketable yield of three peach cultivars [Prunus persica (L.) Batsch. `Autumnglo', `Harvester', and `Redhaven'] when mechanical pruning and harvesting systems were used and trees were grown under three irrigation regimes. All cultivars were trunk-shaken using an experimental inertial shaker on an over-the-row (OTR) shake–catch harvester. `Autumnglo' also was hand-harvested at all irrigation regimes. Fruit damage was not significantly affected by irrigation. A significant source of fruit damage was pruning debris that remained in the canopy after hedging and became lodged in the fruit-conveying system, resulting in cultivar effects on fruit damage. Total yield of firm-ripe fruit was similar among cultivars in 1987 and 1988. However, `Autumnglo' trees had a higher percentage of marketable fruit than `Redhaven' or `Harvester' in 1987 and 1991. Mechanical harvesting appeared to accelerate the decline of `Autumnglo' as shown by tree deaths and greater symptom expression of Prunus necrotic ringspot virus. The potential for a single mechanical harvest of peaches is limited because of the difficulty in managing the ripening window, the high potential for fruit damage, and the possibility of accelerated tree decline for disease-susceptible cultivars.

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D.M. Glenn, W.V. Welker and George M. Greene

Mature peach trees were grown in six different-sized vegetation-free areas (VFAs) (0.36 to 13 m2) with and without stage 3 drip irrigation for 6 years. As VFA size increased, so did the trunk cross-sectional area, canopy diameter, total yield/tree, large fruit yield/tree, and pruning weight/tree. The yield efficiency of total fruit and large fruit initially increased with the increasing size of VFAs and then remained stable over the range of VFAs. Applying supplemental irrigation increased yield of large fruit and leaf N percentage in all VFAs. Cold hardiness was not affected by VFA size or irrigation treatment. The smaller VFAs resulted in smaller, equally efficient trees. Sod management was an effective, low-cost approach to controlling peach tree size, and, when combined with irrigated, high-density production, potentially increased productivity.

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T.J. Tworkoski, D.M. Glenn and W.V. Welker

Carbohydrate and nitrogen were measured during 1992 and 1993 in shoots of peach [Prunus persica (L.) Batsch.] trees that were planted in 1989 and grown in three vegetation-free areas contained within plots planted to tall fescue (Festuca arundinacea Schreber), orchardgrass (Dactylis glomerata L.), or a mixture of Lolium perenne L. and Festuca rubra L. Trees grown in 9.3-, 3.3-, and 1.5-m2 vegetation-free areas had the greatest to the least fruit yield, respectively. Fruit number and mass were negatively correlated with stem mass. Grass type had little effect on mass, carbohydrate, or N partitioning within the tree. Individual sugars and carbohydrate partitioning were not affected by grass competition. In contrast, the proportion of shoot N partitioning into stem and leaves declined markedly as the size of the vegetation-free area increased. Proximity of peach trees to grass may have limited N uptake, which, in turn, reduced fruit yield but not stem and leaf growth.

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D.M. Glenn, T. Tworkoski, R. Scorza and S.S. Miller

The lack of dwarfing rootstocks for peach has led to cultural and genetic approaches that reduce tree size and vegetative growth to establish high-density plantings. The objectives of the study were to evaluate the interactions of pruning strategies, groundcover management, tree densities, and peach (Prunus persica) architecture combined in eight peach production systems on components of yield and economic value. The use of sod management reduced pruning time and costs, but the reduction of crop load reduced net return. High-density plantings in large vegetation-free areas (VFAs) had greater economic return than low-density plantings.

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David M. Modise, Michael D. Glenn and Morris Ingle

The split root technique was used to study water afflux in peach [Prunus persica (L.) Batsch] from wet to dry soil through root systems that bridge wet and dry soil. Peach trees conduct hydraulic lift (HL) to ameliorate water deficits in dry soil layers, under conditions of low transpirational demand. The objectives of this study were to examine the magnitude of HL in peach and to determine its effect on nutrient uptake from dry soil. In addition, the split root system was used to measure peach water uptake from soil supporting `Kentucky 31' tall fescue [Festuca arundinaceae (Schreb)] and determine the diurnal partitioning of water use from covered and bare soil treatments. A Scholander pressure bomb was used to record hourly measurements of water potentials (10 am to 4 p m), daily for a total of 14 days in 3 replicates (1 tree/rep.). Leaf stomata1 resistance was measured using a porometer, simultaneously with the water potential measurements. The CR 7 datalogger was used to record water transfer into the dry root section. 15N was applied in the 15-30 cm root zone, and the concentration in the leaves was determined using a mass spectrometer. Results obtained will be discussed in relation to objectives stated above.

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T. Daw, T.J. Tworkoski and D.M. Glenn

Shoot growth of peach trees can be managed by manipulating edaphic conditions such as root volume and soil fertility. In this experiment, 2-year-old peach trees (Prunus persica L. cv. Sentry on `Lovell' rootstock) were planted in pots with a split root design, so that half the roots were not treated and the other half received one of four treatments: root volume restricted with polypropylene nonwoven fabric (FAB), fertilizer alone (FER), FAB + FER, and untreated control (UTC). Total shoot growth and root growth were measured, and root growth in the split halves was compared. FER increased leaf number and weight by 48% and 60%, respectively, but not stem growth. Leaf nitrogen concentration and photosynthesis were greatest in FER treatment. FAB did not affect shoot weight or reduce total root weight or length, although roots did not grow past the fabric barrier. FER increased root weight and length (116% and 57%, respectively, compared to UTC) on the treated half but did not affect root growth on the untreated half. Greatest root growth occurred in the root half that received FAB + FER, particularly in the 5-cm soil segment proximal to the fabric (4.6 cm•cm-3 compared to 0.8 cm.cm-3 in UTC). Shoot length was greater in FAB + FER than FAB. Thus, fertilizer applied near fabric increased root growth and the combination of fertilizer and fabric may be used to regulate shoot growth. Specific root length (root length per gram dry weight) was highest in trees with no treatment, suggesting root acclimation to low nutrient soil conditions. Lower specific root length resulted in soils that were fertilized. The results indicate that nonwoven fabric restricts root growth in peach trees and reduces shoot elongation. The combined effect of fabric plus selected application of fertilizer may be used to regulate growth of peach trees.

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Fumiomi Takeda, Michael E. Wisniewski and D.M. Glenn

Hydathodes of young, folded strawberry (Fragaria × ananassa Duch.) leaves had unoccluded water pores With various sized apertures, as observed by low-temperature scanning electron microscopy. Hydathodes of fully expanded leaves were brownish and the water pores within the hydathodes were covered with a solid material, presumably comprised of epicuticular waxes and substances excreted through the hydathodes. The entire water pore area of the hydathode was occasionally covered with a shield-like plate. The shield-like plate over the hydathode water pores impeded water flow even with an induced positive pressure. Mechanical scraping of the hydathode area eliminated impedance to water conduction. These observations suggest that external occlusion of water pores in the hydathodes is the resistance component associated with the absence of guttation in older strawberry leaves.

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D.M. Glenn, J. Kotcon and W.V. Welker

Three soil management treatments (cultivation, herbicide, and killed sod) were established in the drive middle of a 10-year-old apple orchard removed the year prior to planting peaches. The cultivation and herbicide treatments used preplant tillage, leaving a bare soil surface, whereas the killed-sod system was untilled. Peach trees (Prunus persica L. Batsch) were planted, and growth, yield, and soil bulk density were measured after 3 years. There were no differences in tree growth or yield for the three treatments These results were contrary to published reports that the killed-sod system increased early tree growth. The lack of growth response in the killed-sod system was attributed to the high soil bulk density remaining from the previous orchard. We concluded that truck and tractor traffic in the drive middle causes severe soil compaction, which may limit root development. The soil compaction can only be moderated by tillage.

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D.M. Glenn, G. Puterka, T. van der Zwet and R. Byers

Fruit production requires extensive use of pesticides to control pest damage and maintain high product quality. Hydrophobic particles alter the leaf surface due to the hydrophobic and reflective nature of the particles and impart characteristics that make the plant surface incompatible, and/or unrecognizable to the pest. Hydrophobic particles were applied to apple and pear in field and greenhouse studies. Specific diseases, insect pests, plant growth, and yield were monitored and evaluated on treated plants in comparison to untreated and chemically treated controls. Powdery mildew in apple and Fabrea leaf spot in pear were controlled by the hydrophobic particles. Aphids, mites, and psylla were controlled in apple and pear. Hydrophobic clays have the potential of cross-protection for several disease and insect pests while imparting beneficial horticultural effects that would increase long-term productivity and sustainability of fruit production systems.