An irrigation control valve that uses the suction developed in a tensiometer to start and stop the flow of water to the irrigation system without the need of electricity was constructed. When soil water suction reached –22 cbars at 25 cm, the valve opened and then closed at –18 cbars. Peach trees at 6 × 6 m (three trees per plot) or 4.9 × 3 m (five trees per plot) spacing were irrigated with either pulse microsprinkler or drip irrigation. Evapotranspiration (ET) was calculated from pan evaporation and adjusted for each plot, based on canopy diameter. Flow meters measured water use for each plot in a split plot design with six replications. In Sept. 1995, drip ET was 30%, and pulse ET was 200% of calculated ET for both plant spacings. Spatial variability in actual and calculated plot ET was >200%, and actual plot ET was highly correlated with calculated plot ET. Data for the 1996 field season will be presented. The results indicate that spatial variability in water use is high, and the tensiometer valve is effective and reliable in scheduling irrigation in a heterogeneous environment.
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).
Peach (Prunus persica L. Batsch) trees were grown for five growing seasons in uniform-sized vegetation-free areas arranged in three patterns within a tall fescue (Festuca arundinacea Schreb.) sod. Trees grown in a vegetation-free area arranged in a strip pattern grew better than trees grown either in the center or edge of a square. The distribution pattern of the vegetation-free area influenced growth during the first 4 years; however, at the end of 5 years, differences in canopy width and trunk cross-sectional area were minimal. Thus, there is much latitude in distributing the available vegetation-free area as orchard floor management practices dictate.
In reciprocal grafts of tall (`Elberta' and `Loring') and dwarf (`Empress' and `Juseito') peach (Prunus persica Batsch.) phenotypes, we measured dry-matter partitioning, resistance to root system water flow, and phytohormone content of xylem exudate. Scion characteristics determined the phenotype and growth characteristics of the tree irrespective of the rootstock. Tall phenotypes had higher dry weight and lower root resistance to water flow than dwarf phenotypes. Cytokinin-like activity and auxin levels in xylem sap were higher in dwarf than in tall phenotypes; whereas gibberellin-like activity was unaffected by either rootstock or scion. The scion of peach influenced phytohormone levels and resistance to water flow in the root system in addition to root and shoot growth.
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.
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.
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.
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.
The water status of strawberry (Fragaria х ananassa Duchesne) was indicated by the occurrence of guttation. Guttation was present when pre-dawn leaf water potential (PLWP) was greater than -0.07 MPa and absent when PLWP was below – 0.11 MPa. Plants exhibiting guttation had greater stomatal conductivity and lower leaf – air temperature at midday, indicating a greater transpiration rate. Hydathodes on older leaves did not consistently express guttation; thus, the occurrence of guttation must be evaluated on young leaves.