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Charles A. Mullins and R. Allen Straw

Several pod characteristics were evaluated to select methods for determining optimum maturity for mechanical harvest of flat podded `Roma II' beans (Phaseolus vulgaris L.). The test was conducted over a 3-year period (1993-1995) at Crossville, Tenn. A total length of 3.6 to 4.4 inches (90 to 112 mm) for the center seed from each of 10 of the more mature pods was a rather reliable and rapid field guide for determining optimum maturity for mechanical harvest of `Roma II' bush beans.

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Donald L. Peterson

Hand-harvesting fruit crops is labor-intensive, and the supply of dependable, skilled labor is a concern of the fruit industry. Only a small portion of all fruit crops is harvested mechanically, primarily for processing. Public funding of mechanical harvesting research on fruit crops has reached a low level. However, there is renewed interest in mechanical harvesting research due to the potential scarcity of hand-harvest labor and new federal laws that may deplete further the labor pool. Much of the research expertise in mechanical harvesting of fruit crops has been lost, since most projects have been discontinued. Considerable lead time will be required to develop facilities, personnel, and projects if the decision is made to initiate publicly funded harvest mechanization research. More time will be required before commercially acceptable techniques and methods will be available. A majority of the research described in this paper was conducted outside the United States. The United States will not remain competitive in the world market for fruit crops with the present lack of mechanical harvesting research.

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Kuo-Tan Li, Jim Syvertsen, and Jackie Burns

Mechanical harvesting using trunk shakers on late-season `Valencia' sweet orange [Citrus sinensis (L.) Osb.] trees can remove young fruit for the next crop and occasionally cause root exposure or severe bark scuffing on the trunk. To evaluate the effects of these physical injuries on fine root growth and lifespan, we installed minirhizotrons in the root zone of 15-year-old fruiting `Valencia' trees on Swingle citrumelo [C. paradise Macf. × Poncirus trifoliate (L.) Raf.] rootstocks. Images of roots against the minirhizotron tubes were captured biweekly with a custom-made video-DVD recorder system. Trees were harvested in early June by hand or with a linear-type trunk shaker in two consecutive years. Bark injury after trunk shaking was mimicked by removing part (42%) of the bark tissue from the main trunk with a sharp knife. Numbers of fine roots, root activity and lifespan as indexed by the color of the root, and the distribution of new fine roots after harvest were analyzed. Although root exposure was common with the normal operations during mechanical harvesting, few disturbances reached the major fine root zone. There was no clear correlation between root growth and trunk shaking with or without bark injury. The root system might benefit from less competition after the loss of young fruit from mechanical harvesting, as a greater availability of carbohydrates or other resources may compensate for any potential damage due to mechanical harvesting.

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Jorge E. Arboleya, Joseph G. Masabni, Michael G. Particka, and Bernard H. Zandstra

Dry bulb onion (Allium cepa) leaves may not dry down normally and bulbs may not attain dormancy during adverse growing seasons. An effective method of artificial leaf desiccation is needed to complement mechanical harvesting and onion conditioning for storage. Desiccants were tested in 1993, 1994, 1995, 2001, 2002, 2003 on onion leaves prior to harvest, and bulb quality was evaluated after 5 months or more of storage. Carfentrazone, diquat, and paraquat desiccated onion foliage well but increased bulb rot and reduced the percentage of marketable bulbs after storage. Bromoxynil and endothall desiccated onion foliage significantly without inducing rot or reducing the percentage of marketable bulbs. Copper sulfate and pelargonic acid increased desiccation of onion foliage but were not sufficiently effective for field use. Neither reduced the percentage of marketable bulbs. If bromoxynil or endothall were labelled for onion desiccation, they could be applied 10-14 days before harvest to enhance natural leaf senescence and facilitate mechanical harvest.

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Galen K. Brown

Hand picking, by snapping each fruit from its stem, has been the traditional method of harvesting Florida oranges (Citrus sinensis) and grapefruit (C. paradisi) for processing. A harvest mechanization program was active from about 1960 to 1985, but mechanical methods were not adopted. In July 1994, a new harvesting research and development program was initiated by the Florida Department of Citrus. The growers are taxed about $0.01/field box of production to fund the program. An industry Advisory Council oversees the program, and recommends projects and funding. The new program has provided training videos to improve hand harvest management/productivity, developed several methods for mechanical harvesting, and discovered/evaluated several fruit abscission agents. Mechanical harvesting use is increasing, and about 6880 of the 237,498 ha (17,000 of the 586,859 acres) of oranges were mechanically harvested during the 2002-03 season. Two mechanical systems can increase labor productivity by 5 to 15 times and reduce unit harvesting cost by 50% or more. Such savings are essential for effective competition in free-trade markets and for operation with resident labor. Many old-style plantings will need to be replaced over the next 10 years. The harvesting program accomplishments are discussed.

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D.L. Peterson

Deciduous tree fruit crops such as apple (Malus domestica), peach (Prunus persica), and sweet cherry (Prunus avium) are not mechanically harvested for the fresh market. Attempts to mechanically harvest these fruits by mass removal techniques have not been successful due to excessive fruit damage caused during detachment, fall through the canopy, and collection. Robotic harvesters have not been commercially accepted due to insufficient fruit recovery. A U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) harvesting concept shows promise for harvesting both fresh market quality apples and sweet cherries. Successful mechanical harvesting of fresh market quality deciduous tree fruit will only occur when plant characteristics and machine designs are integrated into a compatible system. Cultivar characteristics that would facilitate machine harvesting are uniform fruit maturity at harvest, firm fruit that are resistant to mechanical damage, and compact growth habit that produces fruit in narrow canopies and on short/stiff limbs. Engineers must develop new detachment principles that minimize the energy input to effect fruit detachment, and develop durable energy-absorbing catching surfaces/conveyors to eliminate damage during collection of the fruit. As technology advances, sorting and sizing systems might be developed that can be operating on the harvester to eliminate culls in the field and deliver only fresh market quality fruit to the packers.

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Brian A. Kahn, James R. Cooksey, and James E. Motes

Raw seed, primed seed, and transplants were compared for effects on stand establishment, plant morphology, and yield of paprika pepper (Capsicum annuum L.) Raw seed seemed satisfactory for stand establishment, although primed seed had the potential to provide better initial stands. When populations were equalized, there were few differences in plant growth, plant morphology, or fruit yield attributed to seed treatment. Morphology of plants established by direct seeding generally was favorable for mechanical harvest. Use of transplants did not result in higher marketable fruit yields than direct seeding in two out of three years. When compared to plants established by direct seeding, three trends were consistent across all three years for plants established by transplanting: a) they were more massive: b) they had larger vertical fruiting planes: and c) they had more branches. These traits would increase the difficulty of mechanical harvest and would create the potential for more trash in the harvested product. Thus, transplanting is not recommended for stand establishment of paprika intended for mechanical harvest.

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A.R. Gonzalez, D.E. Smith, A. Mauromoustakos, and M. Davis

A study was conducted to evaluate the possibility of producing and processing immature cowpea (Vigna unguiculata) green pods by using the same technology used for green beans (Phaseolus vulgaris). The cowpea cultivar Bettersnap developed for green pod production and the green bean cultivars Benton and OSU-5402 were produced under the same cultural conditions. `Bettersnap' yielded less than 0.5 ton/ha, while `Benton' and `OSU-5402' produced about 2.5 ton/ha in once-over simulated mechanical harvest. `Bettersnap' had long vines and dense foliage, which resulted in plants with more width and less erectness than `Benton', the predominant green bean cultivar. Uneven pod setting and long pods (23.8 cm) in `Bettersnap' constitute potential problem for mechanical harvest. Canned cowpea pods of sieves 2 and 3 had darker green color, smaller seeds, and higher shear value, fiber content, and sloughing than green bean pods. Our study indicates that there is a need to develop cultivars with high yield potential and concentrated pod setting adapted to mechanical harvest with pods containing less fiber and less tendency to sloughing.

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Blair Buckley and Katharine Pee

Ease of pod detachment is an important consideration when selecting cultivars for mechanical harvest at the mature-green stage. Sixteen southernpea cultivars and breeding lines were evaluated for pod detachment force. The cultivars varied in pod detachment force. MN-13 had the largest detachment force with a measurement of 2.18 kg. Royal Cream had the smallest detachment force with a measurement of 1.2 kg. Pod length, pod diameter, pod weight, basal pod fill, and length of peduncle synapse was recorded for each pod sampled for detachment force. There was no clear association between pod detachment force and the five traits.

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Kay P. Gersch, Carl E. Motsenbocker, and Gregory A. Lang

Cayenne pepper fruit adhere tightly to the calyx/receptacle, increasing the cost of hand harvest and restricting mechanical harvest. Eight (8) cayenne pepper genotypes were selected from field observations to characterize fruit detachment forces(FDFs) and examine potential relationships between FDF and other fruit parameters. A preliminary greenhouse experiment revealed two genotypes with consistently lower FDFs and two with consistently higher FDFs over several progressive harvest. A field experiment confirmed these characteristics. No correlation between any fruit parameter and FDF was found to be consistent over the genotypes studied.