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Charlotte M. Guimond, Preston K. Andrews and Gregory A. Lang

Young sweet cherry (Prunus avium) trees are typically upright, vegetatively vigorous, and nonprecocious, taking 5 to 6 years to come into production. To produce fruit in high-density orchards by year 3 or 4, development of lateral shoots for potential fruiting is critical in year 2 or 3. An experiment was designed to promote lateral branching on 2-year-old trees. The experiment was conducted in a commercial orchard in Roosevelt, Wash., with `Bing' and `Van' on the vigorous rootstocks Mazzard and Colt. The trees were planted at 415 trees per acre with three scaffolds trained into a “V” canopy design. The experimental variables were treatments with and without Promalin (1.8% BAP plus 1.8% GA4+7), applied at a ratio of 1:3 in latex paint at green tip stage; superimposed on these treatments were either heading cuts of each scaffold to 2 m long (or tipping the scaffold if it was <2 m), removing four to five buds subtending the terminal bud, a combination of heading and bud removal, or controls. On trees that were not treated with Promalin, three additional treatments included either removing subtending buds at budbreak, or removing buds at multiple locations along the scaffold at green tip or at budbreak. New lateral shoots were counted 4 weeks after budbreak, and the quality of the shoots (shoot diameter and angle of emergence) was measured at the time of summer pruning. Interactions between Promalin, bud manipulation, and pruning will be discussed in relation to development of canopy structure.

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Charlotte M. Guimond, Preston K. Andrews and Gregory A. Lang

Flower initiation and development in `Bing' sweet cherry (Prunus avium L.) was examined using scanning electron microscopy. There was a 1- to 2-week difference in the time of initiation of flower buds on summer pruned current season shoots (P) compared to buds borne on unpruned shoots (U) or spurs (S). By late July, this difference was obvious in morphological development. The P buds had already formed floral primordia, while the S and U buds showed little differentiation in the meristem until early August. In general, buds from unpruned shoots were similar developmentally to spur buds. By late August, primordial differentiation was similar in the buds from all the wood types; however, buds from pruned shoots were significantly larger (838 μm) than buds from spurs (535 μm) and unpruned shoots (663 μm). Early summer pruning may shift allocation of resources from terminal shoot elongation to reproductive meristem development at the base of current season shoots. The similarity in reproductive bud development between spurs and unpruned shoots, given the difference in active terminal growth, might suggest that developmental resources are inherently more limiting in reproductive buds on spurs.

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Michael J. Willett, Preston K. Andrews and Edward L. Proebsting

The techniques of task analysis and task allocation were applied to the problem of decision support system development in tree fruit production. The task of midwinter freeze protection of peach and nectarine [Prunus persica (L.) Batsch] flower buds was chosen as the model system. Sixty-five tasks and subtasks were identified as necessary components of the freeze-protection activity at the testing and subsequent management activity levels. Of these, 45 were done exclusively in the orchard where we wished to focus our efforts to benefit the broadest group of growers. Of these 45 tasks or subtasks, 13 were judged suitable for computerization. These 13 tasks were prioritized in order of importance to growers through a self-administered mail survey that asked how often they would use a computer to perform each task. Based on a 77% rate of return, peach and nectarine growers indicated that they were most likely to use a computer to monitor weather forecasts for general weather and freeze alerts, monitor real-time orchard temperatures, and estimate critical temperature ranges for flower-bud damage. This close interaction also produced additional design and use information for the proposed knowledge-based system, such as data presentation requirements, the presence of a variety of farming styles that often determined how the critical temperature data were produced and used, and the challenges of developing suitable validation data for the users.

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Preston K. Andrews, David J. Chalmers and Mapasaka Moremong

Temperature differences between tree canopies and air (Tc - Ta) and between leaves and air (T1 - Ta) of apples (Malus domestics Borkh. `Royal Gala') grown in New Zealand were measured with infrared (IR) thermometry. Treatments included three orchard-floor management systems and irrigation withheld (WI) for part of the growing season. Measurements of soil moisture indicated that, under full irrigation (FI), an alfalfa orchard-floor system apparently had higher soil water content than herbicide-strip (H) or plastic-mulch systems, whereas under the drought stress of WI, the H system retained the most water. The Tc - Ta and T1 - Ta of the WI treatment were significantly greater than those of the FI treatment after a soil-moisture differential was established. Linear regression between Tc - Ta, or T1 - Ta, and vapor pressure deficit (VPD) exhibited variable responses among dates. A crop water stress index (CWSI) was calculated from environmental measurements. The calculated CWSIS were not related to soil-moisture measurements. Even 35 days after full irrigation had been reinstated on the WI plots, the Tc - Ta, T1 - Ta, and CWSI of the WI plots were still significantly greater than those of the FI plots. These discrepancies in IR thermometry-based water-stress indices may be due to increased errors in the calculation of minimum CWSI at low VPDS and to fluctuating solar radiation and evapotranspiration, which are prevalent in humid, temperate climates.

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Gregory M. Peck, Preston K. Andrews, John P. Reganold and John K. Fellman

Located on a 20-ha commercial apple (Malus domestica Borkh.) orchard in the Yakima Valley, Washington, a 1.7-ha study area was planted with apple trees in 1994 in a randomized complete block design with four replications of three treatments: organic (ORG), conventional (CON), and integrated (INT). Soil classification, rootstock, cultivar, plant age, and all other conditions except management were the same on all plots. In years 9 (2002) and 10 (2003) of this study, we compared the orchard productivity and fruit quality of `Galaxy Gala' apples. Measurements of crop yield, yield efficiency, crop load, average fruit weight, tree growth, color grades, and weight distributions of marketable fruit, percentages of unmarketable fruit, classifications of unmarketable fruit, as well as leaf, fruit, and soil mineral concentrations, were used to evaluate orchard productivity. Apple fruit quality was assessed at harvest and after refrigerated (0 to 1 °C) storage for three months in regular atmosphere (ambient oxygen levels) and for three and six months in controlled atmosphere (1.5% to 2% oxygen). Fruit internal ethylene concentrations and evolution, fruit respiration, flesh firmness, soluble solids concentration (SSC), titratable acidity (TA), purgeable volatile production, sensory panels, and total antioxidant activity (TAA) were used to evaluate fruit quality. ORG crop yields were two-thirds of the CON and about half of the INT yields in 2002, but about one-third greater than either system in 2003. High ORG yields in 2003 resulted in smaller ORG fruit. Inconsistent ORG yields were probably the result of several factors, including unsatisfactory crop load management, higher pest and weed pressures, lower leaf and fruit tissue nitrogen, and deficient leaf tissue zinc concentrations. Despite production difficulties, ORG apples had 6 to 10 N higher flesh firmness than CON, and 4 to 7 N higher than INT apples, for similar-sized fruit. Consumer panels tended to rate ORG and INT apples to have equal or better overall acceptability, firmness, and texture than CON apples. Neither laboratory measurements nor sensory evaluations detected differences in SSC, TA, or the SSC to TA ratio. Consumers were unable to discern the higher concentrations of flavor volatiles found in CON apples. For a 200 g fruit, ORG apples contained 10% to 15% more TAA than CON apples and 8% to 25% more TAA than INT apples. Across most parameters measured in this study, the CON and INT farm management systems were more similar to each other than either was to the ORG system. The production challenges associated with low-input organic apple farming systems are discussed. Despite limited technologies and products for organic apple production, the ORG apples in our study showed improvements in some fruit quality attributes that could aid their marketability.

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David J. Chalmers, Preston K. Andrews, Kevin M. Harris, Ewen A. Cameron and Horst W. Caspari

The design of a type of drainage lysimeter, as tested with trees of Pyrus serotina Rehder var. culta Rehder `Hosui' is described. All lysimeter operations and monitoring of irrigation and drainage volumes were managed by a “multi-tasking” controller/datalogger. It was possible to apply different irrigation levels to each of three sets of four random lysimeters. Evapotranspiration (ET) was calculated using a conservation of water equation, with differences between irrigation inputs and drainage outputs corrected for changes in soil-water content. ET ranged between 3.3 and 10.7 liters/tree per day in well-watered, noncropped trees in late Summer and Fall 1990. These rates correspond to ET of 0.13 to 0.43 liter·cm-2·day-1 and 0.96 to 3.10 liters·m-2·day-1 on trunk cross-sectional area and canopy area bases, respectively. The correlation coefficient between ET and Class A pan evaporation was >0.9 during this period. Weekly crop coefficients for the well-watered trees averaged 0.52 when calculated on a canopy-area basis. When irrigation was withheld for 18 days, the crop coefficient declined to 0.38. There were no differences in ET between trees growing in the two soil profiles, despite significant differences in soil water distribution.