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  • Author or Editor: Louise Ferguson x
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Developing mechanical harvesting is the most effective, and most difficult, factor in improving horticultural crop profitability. It requires simultaneous incremental changes by multiple entities; engineers, horticulturists, food scientists, economists, local extension personnel, the commercial harvester industry, growers, and displaced laborers and their management. There is a narrow annual testing window. The initial research by engineers and horticulturists focuses on developing effective removal technologies and can be applied or basic. When funding is local, the research is generally applied and is usually an adaptation of existing technology. With national funding, the research is basic or investigates novel technologies. Both are conducted first on model systems or individual plants. Properly executed, both types can be published, but publication is difficult if engineering parameters are changed during the trials. Evaluation of developed removal technologies requires cross-disciplinary teams to evaluate the effects on the final marketable product quality and long-term plant health. Publications can be produced on testing technology or effects on marketable product quality or plant health. An industry education program with field days, industry publications and websites, and annual presentations should frequently report progress. Finally, a prototype should be demonstrated to show the economic feasibility of a mobile platform with catching technology. The research team then expands to include the harvester industry and grower cooperators. Orchard adaptations to increase harvester efficiency are incorporated at this point. Usually by this time all research is applied and the funding local. If results demonstrate economic feasibility, the technology should now segue to the commercial harvester industry as university laboratories mostly lack the capacity to generate truly commercial harvesters. Publications could be delayed to avoid premature disclosure to make patents achievable and to facilitate cooperation between university researchers and commercial fabricators.

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Knowing a tree crop’s seasonal growth and development as a function of heat accumulation can facilitate scheduling of irrigation, pesticide applications, and harvest. Our objective was to compare the goodness of fit of applied models and determine which provides the best description of pistachio nut growth as a function of thermal unit accumulation. Three fruit growth traits of pistachio—pericarp (hull) + endocarp (shell) size, endocarp thickening and hardening, and embryo (kernel) size—exhibited clear nonlinear dependence on heat accumulation. We tested three nonlinear models—Michaelis–Menten, three-parameter logistic, and Gompertz—fitted to fruit development data to create a tool to forecast pest susceptibility and harvest timing. Observation of development began at full bloom and ended at harvest. Data were collected from six pistachio cultivars in one experimental and eight commercial orchards over 3 years. Analyses of residual distribution, parameter standard errors, coefficient of determination (R 2) and the Akaike information criterion (AIC) all demonstrated the Gompertz function was the best model. Cultivars differed significantly in all the three parameters (Asym, b, and c) for all three traits with the Gompertz model, demonstrating the Gompertz model can adjust to incorporate cultivar differences. The growth curve of the three traits together provided integrated information on nut biomass accumulation that facilitates predicting the critical timing for multiple orchard management practices.

Open Access

Pecan [Carya illinoinensis (Wangenh.) K. Koch] is a member of the Juglandaceae family. During spring, pecan trees break their bud dormancy and produce new leaves and flowers. Carbohydrates stored in roots and shoots are thought to support the bloom and early vegetative growth during this time until new leaves start the full photosynthetic activity. Spring freeze is known for its damaging effects on pecan bud and flower growth and development. Pecan shoots with leaves and flowers from five scion–rootstock combinations were collected hours before and after a recent spring freeze (below 0 °C for 6 hours, 21 Apr 2021, Perkins, OK, USA). Morphologies of the leaf, bud, and catkin were visually observed, and the morphologies of the anther and pollen in paraffin sections were investigated by light microscopy. Soluble sugar and starch from bark and wood were analyzed using the anthrone reagent method. The Kanza–Mount showed the maximum damage to terminal leaves, buds, and catkins, whereas Maramec–Colby had the minimum damage only to leaves. Pollen grains were shrunk and reduced in number in the anthers in the protandrous Pawnee scions, whereas no pollen damage was observed in the protogynous Kanza scion. Furthermore, bark soluble sugar levels increased in all the scion–rootstock combinations after the freeze, which may indicate a physiological response to the cold stress. Overall, the extent of spring freeze damage of pecans is affected by the growth stage, types of scion and rootstock, and the scion–rootstock interactions. Furthermore, in addition to low temperature, scion–rootstock interactions also affected the starch and soluble sugar contents in wood and bark tissues.

Open Access

Table olives (Olea europaea) traditionally are hand harvested when green in color and before physiological maturity is attained. Hand harvesting accounts for the grower's main production costs. Several mechanical harvesting methods have been previously tested. However, tree configuration and fruit injury are major constraints to the adoption of mechanical harvesting. In prior work with a canopy shaker, promising results were attained after critical machine components were reconfigured. In this study, stereo video analysis based on two high-speed cameras operating during the harvesting process were used to identify the sources of fruit damage due to canopy-harvester interaction. Damage was subjectively evaluated after harvest. Fruit mechanically harvested had 35% more bruising and three times as many fruit with broken skin as that of hand-harvested fruit. The main source of fruit damaged in the canopy was the strike-impact of fruit by harvester rods. Implementation of softer padding materials were effective in mitigating fruit injury caused by the impact of rods and hard surfaces. Canopy acceleration was correlated with fruit damage, thus restricting improvements needed for fruit removal efficiency through increased tine frequency.

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