FIELD EVALUATION OF FRUIT DETACHMENT OF MACHINE

Transcription

1 126 FLORIDA STATE HORTICULTURAL SOCIETY, 1968 Acknowledgment LITERATURE CITED Appreciation is expressed to Parnell and Associates, Inc., Orlando, Florida for supplying a bean sizer for this study. 1. Brooke, D. L. and A. H. Spurlock, Cost of harvesting snap beans by machine. Florida Agricultural Experiment Stations, Agricultural Economics Mimeo Report EC 68-2: Burdine, H. W. and V. L. Guzman Effects of spacing between rows and between plants on growth and yield of three celery varieties. Proc. Fla. State Hort Soc. 12: Wolf. E. A Florida 683 A Utah-type celery. Florida Agricultural Experiment Stations, Circular S-156:4. FIELD EVALUATION OF FRUIT DETACHMENT OF MACHINE HARVEST TOMATO VARIETIES WITH A PORTABLE SHAKER ElCHARD C. FLUCK Agricultural Engineering Department University of Florida, Gainesville James W. Strobel Gulf Coast Experiment Station, Bradenton Herbert H. Bryan Sub-Tropical Experiment Station, Homestead Abstract Numerous constraints limit achievements in solving a recalcitrant problem such as the me chanical harvesting of fresh-market tomatoes. Among these are the biological limitations in herent in the breeding program limiting the ex tent a new line may differ from the available parentage and the necessary time interval to produce a new crossing. Also there are the en gineering limitations based upon availability of materials and components and the physical feas ibility of a particular combination of components in a machine. A stationary, portable field shaker was used to evaluate several breeding lines in a simultane ous exploration of biological and engineering potentialities. Biological factors explored in cluded the reaction of tomatoes incorporating the jointless characteristic to a shaking action imparted to the vine and the effect of a delay allowing for plant dehydration between cutting Florida Agricultural Experiment Stations Journal Series No and shaking the vines. An engineering factor explored was the optimum combination of shaker stroke and frequency resulting in most efficient fruit removal from the vines. Introduction Mechanical harvesting of tomatoes for fresh market consumption is a goal now being pur sued by several research teams. The desired attainment of this goal is made difficult by the inability to predict harvest dates and schedule planting accordingly, the lack of concentration of fruit maturity at a mature green or breaker stage, the inherent difficulties in gathering fruit growing almost at random in a complex matrix of vines, the difficulties in selecting marketable fruit among all picked fruit, and the necessary minimization of fruit injury, to name a few. An interdisciplinary approach is mandatory to solve a problem beset by such complexities. A solution, a workable mechanical harvesting sys tem, must be developed within certain limita tions or constraints, some of which are of a biological nature and some of which are of a physical nature. Examples of biological con straints are the genetic material available to a plant breeder, the tenacity with which a fruit remains attached to the vine, and the ability of the fruit to withstand mechanical induced in jury. Examples of physical constraints are the availability of materials and components for a machine, the feasibility of combining particular available components into a machine, and the minimum velocities required to transport fruit on a machine to obtain an economically feasible harvesting rate.

2 FLUCK, STROBEL, BRYAN: TOMATO HARVESTER STUDIES 127 In order to investigate the nature of several constraints concerning tomato fruit detachment a portable shaker was used to evaluate tomato fruit detachment characteristics in the field. In particular, constraints which were investigated and reported here were optimum frequencystroke combinations, varietal differences and the responses of the jointless characteristic to a harvester-type fruit separation, and plant dehy dration prior to fruit detachment. Review of Literature Mechanical harvesting of tomatoes for proc essing is current commercial practice (9). Work on the mechanical harvest of tomatoes for fresh market began in 1966 (3) and is now being continued by at least three research teams. (1, 2, 5). Incorporation of the jointless pedicel gene (J2) into varieties suitable for mechanical har vest has been underway since 1961 (12). One function of any tomato harvester must be to separate the tomato fruit from the vine. This in itself is a complex problem having many ramifications and complicating factors. The ef fect of shaker vibration frequency in both hori zontal and vertical planes has been studied (6, 7). One worker (10) concluded that 150 cpm and a 5^ inch stroke in horizontal vibration resulted in best selective separation of combina tions tested up to that level. Others (11) have used 200 cpm and a 4 inch stroke. One harvester (5) subjects plants to an increasing amplitude as the plants pass through, and in this work it was found that separation increased with both increasing stroke and frequency. The separation of fruit from vine by vertically shaking sus pended vines was investigated and shown feasi ble (8). Separation by stripping with rubber fingers has been investigated (4) as yet another alternative. Little work has been reported which makes any effort to compare varietal separation char- SHAKING FRAME) g. l. Portable Tomato Shaker.

3 128 FLORIDA STATE HORTICULTURAL SOCIETY, 1968 acteristics. No publications have been found which report the effect of plant dehydration on fruit separation. Experimental Methods The portable field shaker used in these tests (Figure 1) was constructed of aluminum, pow ered hydraulically, and mounted on a trailer (for portability) pulled by a tractor which served as the power source. The shaker had a horizontal bed measuring 48 in. long by 38 in. wide on which plant-supporting rods could be mounted at various spacings and in either direc tion. The bed was supported by bearings so that it could cycle back and forth when driven by an eccentric from a hydraulic motor. The principle of fruit separation used was chosen on the basis of experience with the FMC ma chine used in a preliminary study (3). In a batch rather than continuous operation plants were placed on the bed, shaken for a predeter mined time, and removed. Tomatoes detached from the vines dropped through the rods into a pan whose height could be adjusted. They were gathered, graded, counted, and weighed. Stroke was adjustable from 2 in. to 9.5 in. in ^4 in. increments. Frequency was continuously adjust able from about 20 to 350 cycles per minute. All tests reported here were run in January of 1967 or 1968 at the Sub-Tropical Experiment Station, Homestead. Preliminary tests were run to determine the length of the shaking interval which would be suitable from both the standpoints of vine flow rate through harvester and fruit detachment. A shaking interval of 5 seconds was selected. At a given stroke-frequency combination most fruit which were detached were detached within about three seconds with few additional ones being detached in the latter two seconds. The selected time interval is also compatible with a reason able forward speed of a harvester and a reason able shaking bed length to accomplish adequate vine flow rate. Stroke-Frequency Combination One test was run with a single experimental line in which both stroke length and frequency were varied. Treatments were every combination of strokes of 3, 4Y2 and 6 inches and frequencies of 150, 190, and 270 cycles per minute. Varietal Responses Nine breeding stocks were grown in separate plots with four plot replications of each line. Ten plants were taken from each replicated plot and the fruit were removed by the shaker which was set at 41/& in. stroke and 200 cpm/ for a 5 sec. interval. Fruits were classified separately by maturity (imma ture, mature, and pink or beyond), whether or not they were removed from the plant and, if so, whether or not the pedicel remained attached to the fruit. The quantity and weight of fruit in each classification was recorded. The breeding stocks included two newly re leased varieties, Tropi-Gro and Tropi-Red, and 7 unreleased jointless lines. The jointless lines have the characteristic which results in many fruit detaching from the vine without a pedicel. Effect of Plant Dehydration Before Shaking Seven plants from each of the 28 plots of the 7 jointless breeding lines were cut and left in the field to dehydrate for periods of 2, 4, and 24 hours. The same measurements were made as on the varietal response trial whose plants were not subjected to dehydrating conditions and the results were compared. It was recog nized that the amount of dehydration of the plant would vary under different atmospheric conditions. Results and Discussion Stroke-Frequency Combinations The per centage of fruit removed from the vine increased with both increasing stroke and increasing fre quency as expected (Figure 2). However, the degree of agitation and the potential for me chanical injury to the fruit also increased as stroke length and frequency increased. There fore there should be an optimum combination of stroke and frequency at which the sum of both the value of marketable fruit left on the vines and the decrease in value due to mechani cal injury would be minimized. That point or set of points was not investigated, but the con tours at which 90% and 95% of the fruit were removed were drawn in Figure 2 by interpola tion. For instance, 95% of the fruit were re moved at a 6 in. stroke and 190 cpm or at a 4^ in. stroke and 230 cpm. Varietal Responses Table 1 gives the per cent of the fruit removed by weight and by num ber with and without pedicels and by maturity for each of the nine lines. The two varieties Tropi-Red and Tropi-Gro had the largest percent fruit removal with al most % of the mature and pink fruit re moved. The remainder of the lines had about

4 FLUCK, STROBEL, BRYAN: TOMATO HARVESTER STUDIES STROKE-IN. Fig. 2. Percent removal of mature/green tomatoes during & Sec. Interval. -% of the combined mature and pink fruit removed except 407-Dll-Sl-D4-BGBk, which had 87% removed, ranging from 78 to 97%. Only the Tropi-Red and Tropi-Gro varieties were not jointless. The percent of pink and ma ture fruit removed without pedicels ran as low as 16% for Tropi-Red and 26% for Tropi-Gro to as high as 52% for 1346-D10-S3-Dl-BGBk. Most of the jointless lines had about 40% of the pink and mature fruit removed without pedicels. Evidently the jointless characteristic, when measured by a simulated harvester component, manifests itself to a varying degree dependent upon variety. This specific characteristic should be improved in further breeding work. Plant Dehydration Prior to Shaking Analy ses of variance on the data (Table 2) showed there were statistically significant differences among the breeding lines in the percentage of the grouped pink and mature tomato fruit re moved from the vines. Total percentage fruit removal was not significantly affected by plant dehydration time, and the percentage removed without pedicels was not significantly different among the seven jointless breeding lines tested. Perhaps the most important result was that increased plant dehydration prior to shaking re sulted in a significant increase in the percentage of the removed fruit which did not have attached pedicels. This effect should be further investi-

5 Remaining FLORIDA STATE HORTICULTURAL SOCIETY, 1968 Table 1. Percent weight tomato fruit removed by shaker 1/ and remaining on vines. "" Removed Without Pedicel Removed With Pedicel Maturity Pink Mature Immature 0 00 CO CM H CM 1/ Shaker operating for 5 sec;, at 4 1/2 in, stroke and 200 cpm.

6 FLUCK, STROBEL, BRYAN: TOMATO HARVESTER STUDIES 131 Table 2. Effect of Plant Dehydration on-fruit Removal Without Pedicels and on Total Fruit Removal. Breeding Line Percent weight fruit removed without pedi cels Dehydration time - Hours Percent total weight fruit removed D3-Dl-BGBk D3-D2-BGBk 2005-D4-BGBk Dll-S2-D3-BGBk Dll-Sl-DlO-BGBk D10-S3-Dl-BGBk Dll-Sl-D4-BGBk gated. Perhaps the combined results of further breeding work and plant dehydration prior to fruit separation could result in a very high percentage of the fruit removal without pedicels. The possibility of detrimental effects on the to mato fruit due to plant dehydration should not be overlooked. Acknowledgment J. F. Beeman designed and constructed the field shaker used in these tests. REFERENCES l. -, Mechanical System for Market To matoes. Western Grower and Shipper, (4) : 21-22, Deen, W. W., Jr., and N. C. Hayslip, Develop ment of Harvester Components for Reduction of Damage to Fresh Market Tomatoes. Indian River Field Laboratory Mimeo Report IRL 68-2, Fort Pierce, Florida. 3. Deen, W. W., Jr., J. W. Strobel, N. C. Hayslip, J. F. Beeman, and C. B. Hall, Preliminary Studies on Mechanical Harvesting of Tomatoes for Fresh Market. Proc. Fla. State Hort. Soc. 79: El Domiaty, A., and C. Lorenzen, Performance Characteristics of a Stripper-Type Separation Unit for To mato Harvesting. ASAE Paper No ASAE, St. Joseph, Michigan. 5. Hood, C. E., and B. K. Webb, Development of Tomato Harvester for the Southeast. ASAE Paper No ASAE, St. Joseph, Michigan. 6. Kampe, D. F., G. M. Hansen, and S. Honma, Fruit Removal Characteristics of Cherry Tomatoes. Quar. Bui. Michigan State Univ.. 50(4) : Lorenzen, C, and G. C. Hanna, Mechanical Harvesting of Tomatoes. Agricultural Engineering 43(1): Mclntosh, F. P., Vertical Vibration for Sepa rating Fresh Market Tomatoes from the Vine. Unpublished M. S. Thesis, Agricultural Engineering Dept., Univ. of Fla., Gainesville, Florida. 9. National Canners Association Agricultural Division, Proceedings of the National Conference on the Mecanization of Tomato Production. Purdue University, Dec Stephenson, K. Q., Selective Fruit Separation for Mechanical Tomato Harvester. Agricultural Engineering 45(5): Stout, B. A., and S. K. Ries, Development of a Mechanical Tomato Harvester. Agricultural Engineering 41(10): Strobel, J. W., Jointless A Gene Important in Tomatoes for Machine Harvest. Fla. Grower and Ranch er, North Edition 75(3): 18D.