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W.V. Welker and D.M. Glenn

Peach [Prunus persica (L.) Batsch] trees were planted in killed sod developed from five different grasses. Tree growth was evaluated within the killed-sod treatments, as well as between killed-sod and bare soil treatments. Canopy width, tree height, and trunk cross-sectional area were all greater in the killed-sod treatments than in the bare soil treatments. All five grasses tested were acceptable for developing a killed-sod mulch. Chemical names used: N-(phosphonomethyl) glycine (glyphosate); N1(3,4-dichlorophenyl)-N,N-dimethylurea (diuron); 5-chloro-3-(1-1-dimethylethyl)-6-methyl-2,4(1H,3H)-pyrimidinedione (terbacil).

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D.M. Glenn and S.S. Miller

The objectives of this 7-year study were to determine the effect of repeated root pruning and irrigation on peach (Prunus persica L. Batsch) tree growth and soil water use. Root pruning began in the year of planting. Peach trees trained to a freestanding “Y” were root-pruned at flowering for 4 years (1985 to 1988) and subsequently at flowering and monthly through July for 3 years (1989 to 1991). Irrigation was withheld or applied the full season or only during stage 3 of fruit growth on root-pruned and non-root-pruned trees. Root pruning limited soil water availability throughout most of the growing season when irrigation was withheld; however, when irrigation was applied, there was no difference in soil water availability. The root length density of peach roots was greatest in the 0 to 30-cm depth, was promoted by irrigation, and was reduced by root pruning in the 0 to 90-cm root zone. Full-season irrigation increased vegetative growth over the nonirrigated treatments. Root pruning had no effect on vegetative growth measured as fresh pruned material. The treatments had no effect on leaf nutrient content, except that root pruning reduced Zn in five consecutive years. Fruit yield was reduced 1 in 5 years by root pruning, and full-season irrigation reduced yield in 3 of 5 years. Repeated root pruning restricted the lateral spread of the root zone and the use of soil resources, yet on the deep soil of this site, restricting the lateral extent of the root zone did not reduce vegetative tree growth.

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T.J. Tworkoski and D.M. Glenn

Peach tree size has been restricted when trees were grown continuously with grass after tree planting. However, control of excess vegetative growth of fruit trees was inconsistent when grass was planted beneath mature trees. This research determined the effect of seven grasses on growth, leaf nitrogen concentration, and yield of 8-year-old peach trees and on weed abundance. Two cultivars (`Loring' and `Redhaven') of peach [Prunus persica (L.) Batsch] trees were planted in separate orchards in 1987 in a split-plot design with grass as a main effect and time as the subplot. Nine treatments were installed as ground covers beneath peach trees in 1995: Festuca arundinacea, Lolium perenne var Manhattan II; L. perenne var. Linn; Agrostis gigantea, Dactylis glomerata, Phleum pratense, Bromus carintus, weedy control, and herbicide control (simazine, glyphosate). In general, grasses reduced vegetative growth and yield in `Loring' and `Redhaven'. For example, compared to herbicide treatments, orchardgrass reduced sprout length by 27% in `Loring' and by 15% in `Redhaven'. Fruit-bearing branch length was reduced with orchardgrass by 30% in `Loring' and 19% in `Redhaven'. Orchardgrass affected fruit yield more than vegetative growth, reducing yield by 37% and 24% in `Loring' (predominantly in the 2- to 2.5-inch size class) and `Redhaven' (predominantly in the >2.5-inch size class), respectively. All grasses were not equally competitive, `Linn' perennial ryegrass never significantly affected growth or yield. Weedy treatments also did not differ from herbicide treatments in peach tree growth and yield. Grasses and weeds consistently reduced peach tree leaf nitrogen by 17% compared to herbicide treatment, but weed density was not correlated with reductions in yield and vegetative growth. The results indicate that peach cultivars respond differently to grass competition but the relative competitiveness of grass species was similar for both cultivars. Grass competition can reduce growth of mature peach trees but this reduction did not translate to reduced pruning time per tree.

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D.M. Glenn, G. Puterka and S. Drake

Particle film technology uses inert mineral particles to envelope a plant in a protective and porous “particle film.” The film appears to protect against insect damage by creating a hostile and unfamiliar environment, causing nonrecognition of the host, acting as an irritant, and giving poor adhesion or gripping of eggs and insects to the plant surface. Being porous, the particle film allows free exchange of water and carbon dioxide from the leaf during photosynthesis. The mineral particles are reflective of infrared radiation and reduce the heat load on the plant. Laboratory, greenhouse, and field trials demonstrate that particle film technology is a viable pest control practice for a wide range of insect and disease problems with additional horticultural benefits due to reduced heat stress. In field studies, reducing heat stress improved red apple color development, increased leaf photosynthetic rates, and increased yield. Particle film technology appears to be a viable alternative to conventional pesticide use in apple and pear production. Particle films have the added benefits of reducing plant heat stress and improving safety to farm workers, consumers, and the environment.

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D.M. Glenn and W.V. Welker

We determined how differences in peach tree water use and shoot and root growth due to ground cover treatments are affected by tree response and soil conditions in the adjacent soil environment. Ground cover combinations of bare soil (BS), a killed K-31 tall fescue sod (KS), a living Poa trivialis sod (PT), and a living K-31 tall fescue sod (LS) were imposed on 50% of the soil surface in greenhouse studies. The ground cover on 50% of the soil surface influenced root and top growth of the peach trees [Prunus persica (L) Batsch], water use, and NO3-N levels in the opposing 50%, depending on the competitiveness of the cover crop (LS vs. PT and KS) and characteristics of the soil (BS vs. KS). Tree growth was allometrically related to root growth.

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D.M. Glenn and W.V. Welker

Planting sod beneath peach trees (Prunus persica) to control excessive vegetative growth was evaluated from 1987 to 1993 in three field studies. Peach trees were established and maintained in 2.5-m-wide vegetation-free strips for 3 years, and then sod was planted beneath the trees and maintained for 5 to 7 years. Reducing the vegetation-free area beneath established peach trees to a 30- or 60-cm-wide herbicide strip with three grass species (Festuca arundinacae, Festuca rubra, Poa trivialis), reduced total pruning weight/tree in 5 of 16 study-years and weight of canopy suckers in 6 of 7 study-years, while increasing light penetration into the canopy. Fruit yield was reduced by planting sod beneath peach trees in 5 of 18 study-years; however, yield efficiency of total fruit and large fruit (kg yield/cm2 trunk area) were not reduced in one study and in only 1 year in the other two studies. Planting sod beneath peach trees increased available soil water content in all years, and yield efficiency based on evapotranspiration (kg yield/cm soil water use plus precipitation) was the same or greater for trees with sod compared to the 2.5-m-wide herbicide strip. Planting sod beneath peach trees has the potential to increase light penetration into the canopy and may be appropriate for high-density peach production systems where small, efficient trees are needed.

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D.M. Glenn and W.V. Welker

The objective was to determine the interrelationship between root growth and plant available soil water (PAW) for young, nonbearing, and mature fruiting peach trees (Prunus persica L. Batsch) over 7 years. Root growth observed with minirhizotrons indicated that young, nonbearing trees developed new white roots throughout the growing season. The pattern of new white root growth became bimodal when the trees fruited. White root production in mature trees appeared in March, preceding budbreak, ceased in June, resumed following fruitremoval in August, and persisted through January. The appearance of white roots was inversely related to the presence of fruit and was not correlated to PAW levels in the 0 to 90 cm depth. The lack of root growth response to PAW levels was attributed to a root system that penetrated the soil to depths beyond our zone of sampling. Circumstantial evidence suggests that deep roots help maintain the surface root system when the surface soil dries.

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D.M. Glenn and W.V. Welker

Seedling `Tennessee Natural' peach [Prunus persica (L.) Batsch] trees were grown in a series of five greenhouse experiments to determine how peach root development was affected by the interaction of soil pressure potential and the presence of Kentucky-31 (K-31) tall fescue (Festuca arundinaceae Schreb.). Peach trees were grown in split-root rhizotrons that had four separate root growth sections. When two of the four sections had live sod (LS) and two remained bare soil (BS), there was no effect of the LS on peach root development when the trees were irrigated daily. Peach root development was reduced in BS and LS treatments when soil pressure potential was less than -0.06 MPa. In contrast, when trees were grown in rhizotrons that had all four sections with either LS or a killed K-31 sod (KS), peach root development was reduced in the LS treatment compared to the KS treatments when irrigated daily or when soil pressure potential reached -0.03 MPa. The apparent root surface water potential of peach trees in the LS treatment was -0.4 MPa lower than that in the KS treatment under daily irrigation due to the interference of the K-31 tall fescue. In two additional experiments using peach trees with BS in all four sections, we maintained three sections at field capacity and allowed one section to dry to -0.06 to 1.5 MPa. During the night, when transpiration was low, water was transferred to the dry soil section via the peach root system from the three wet soil sections. It appears that the root system of peach can maintain root development in the presence of tall fescue by transferring water from regions of high water availability to those of low availability.

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W.Q. Yang and D.M. Glenn

The osmotic potential and development of apple (Malus domestica Borkh.) and peach [Prunus persica (L.) Batsch] floral and vegetative buds and tissue were determined pre- and postbloom. Apple and peach floral and vegetative buds were removed prebloom and the osmotic potential and bud development were measured pre- and postbloom. The osmotic potential of vegetative and floral buds was related to the phenology of bud development. Developing buds had a more negative osmotic potential than dormant buds. Leaf buds on deflorated shoots had a more negative osmotic potential than leaf buds on shoots with floral buds. However, flower buds on defoliated shoots had a less negative osmotic potential than flower buds on shoots with leaf buds.

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D.M. Glenn and W.V. Welker

Planting sod beneath peach trees to control excessive vegetative growth was evaluated from 1987 to 1993 in three field studies. Peach trees were established and maintained in 2.5-m-wide, vegetation-free strips for 3 years, and then sod was planted beneath the trees and maintained for 5 to 7 years. Reducing the vegetation-free area beneath established peach trees to a 30- or 60-cm-wide herbicide strip reduced total pruning weight/tree and weight of canopy water shoots in many years. Fruit yield was reduced by reducing the size of the vegetation-free area in some, but not all, years; however, yield efficiency (kg yield/cm2 of trunk area) was not reduced in two studies, and in only 1 year in the third study. Planting sod beneath peach trees increased available soil water content in all years and yield efficiency based-evapotranspiration (kg yield/cm soil water use + precipitation) in some years compared to the 2.5-m herbicide strip. Reestablishing sod beneath peach trees has the potential to control vegetative growth and may be appropriate for high-density peach production systems where small, efficient trees are needed.