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22 JanuaryMarch 1999 9(1)
Developing Mechanized Systems forProducing, Harvesting, and HandlingBrambles, Strawberries, and Grapes
Justin R. Morris
ADDITIONAL INDEX WORDS. abscission layer, fruit maturity, mechanization systems, mechanicalharvesting, mechanical shoot positioning, mechanical pruning, processing
SUMMARY. Mechanization of harvesting, pruning, and other cultural operations on many smallfruit crops for the processing market has occurred in response to the scarcity and expense ofhand labor. Scientists at the Arkansas Agricultural Experiment Station and other experimentstations in the United States and throughout the world have developed new cultural and fruit-handling systems and have determined the effects of these systems on fruit yield and quality.This research has resulted in the development of prototype and commercial machinery as wellas production and handling systems that have assisted in mechanization systems for brambles,strawberries (Fragaria ananassa Duch.), and grapes (Vitis sp.). Much of this body of work isin commercial use and much is simply available, awaiting circumstances that will be beneficialto implementation.
For some crops, harvest labor accounts for as much as two-thirds ofthe total labor costs. Fruit producers generally use hand laboras long as it is available at a reasonable cost, since mechanizationrequires large capital investments and often reduces the producers flexibility tochange from one crop to another. Consequently, the technology for mechani-zation has usually been developed long before implementation.
Migrant workers have provided much of the harvest labor. Until re-cently, there was little concern for the welfare of these workers by eitherthe employer or the government. Eventually, concern about the problemsof the migrant workers resulted in major changes and improvements inwages, housing, education, and health benefits. These developmentsincreased the cost of harvesting and have led to an increased interest inharvest mechanization so that producers can remain competitive andmaintain an inexpensive supply of fruit for consumers. This interest inmechanization has brought about developments for producing and har-vesting brambles, strawberries, and grapes.
BramblesHARVESTERS. Successful mechanical harvesting systems have beendeveloped for many fruit, with brambles and grapes being outstandingexamples.
Distinguished professor, Institute of Food Science and Engineering, University of Arkansas, 272 Young Ave, Fayetteville AR 72704.
Published with the approval of the Director, Arkansas Agricultural Experiment Station, manuscript #9703. The cost of publishing thispaper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby markedadvertisement solely to indicate this fact.
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The bramble harvester has, with minoradaptations, been used to pick erect andtrellised blackberries (Rubus subg. rubus),black raspberries (Rubus occidentalis L.), redraspberries (Rubus idaeus L.), and gooseber-ries (Ribes hirtellum Michx.). By the mid-1960s, there were 30 commercial machinesoperating in raspberry plantations in theUnited States (Dale et al., 1995). The proto-type developed in 1964 at the University ofArkansas was one of the first harvesters devel-oped and operated by mechanical shaking ofthe canes (Morris et al., 1978b). The canefruit develops an abscission layer at matura-tion, which allows the more mature fruit to beharvested when shaken. All modern self-pro-pelled commercial pickers work on this shak-ing principle using sets of horizontal beaterspositioned in a vertical plane on each side ofthe row (Fig. 1). These improved beater armson the modern commercial harvesters allowfor a reduction in the number of strokesneeded per minute to harvest the fruit, andcause the least amount of damage to the newcanes compared to the original prototype.
The range of 100 to 150 strokes perminute at a ground speed of 1 mph (1.6kmh1) is adequate to harvest only the ripefruit. This frequency of stroke also provides acomplete shaking throughout the hedgerow.This is important, since berries that are al-lowed to remain in the interior of the hedg-erow often develop mold and contaminatethe next harvest. Most self-propelled com-mercial bramble harvesters should have thefeature of being able to be raised, lowered andleveled to fit the plane of the field and theheight of the canes. The need for this capabil-ity is due to the low fruiting habit of many ofthe cane fruit crops. The Arkansas harvestercollects all fruit above 15.5 inches (40 cm)and is only one of several successful cane fruitharvesters currently in use. The commercialmodel of the Arkansas harvester, with oneoperator and four field graders, can do thework of 80 to 85 handpickers.
FRUIT QUALITY. Unlike hand harvesting,machines are able to operate at night to allowfor the harvesting of fruit at a lower tempera-ture (Morris et al., 1978b). Research andexperience have shown that night harvestingis necessary in warm production regions tomaximize fruit quality. The mechanically har-vested fruit can be of better quality thanhand-harvested fruit when all operations arecarried out in a proper and timely manner.Machine-harvested berries are larger and havehigher total soluble solids, lower acidity, andsuperior color compared to hand-harvestedberries, which generally do not have uniformmaturity (Morris et al., 1978b). By machineharvesting at the lowest possible tempera-ture, fruit quality can be maintained during
subsequent handling before processing.Treating brambles with the growth regu-
lator ethephon before harvest can improvethe fruit quality. Ethephon reduces the num-ber of required harvests, increases color, andlowers acidity of both raw and processedblackberries (Morris et al., 1978a; Sims andMorris, 1982). Most insects can be elimi-nated from cane fruit before machine harvest-ing by following recommended spray pro-grams for specific insect problems. Of thosethat remain, 95% can be removed beforeprocessing by a washing technique in whichinfested berries pass through water contain-ing a dilute nonalkaline, anionic wetting agent.There is no loss of quality with this method(Crandall et al., 1966; Christensen et al.,1973).
CULTURAL SYSTEMS. In many cases, modi-fications of old cultural systems must be madeto successfully machine harvest brambles. Amechanical pruner, developed at the Univer-sity of Arkansas, properly shapes the hedg-erow for maximum harvesting efficiency oferect cane fruit (Morris et al., 1978b) andreduces the labor necessary for pruning. Oldcanes left in the hedgerow, do not affect yieldor fruit quality.
Hedgerow culture of erect blackberriesis conducive to mechanical harvesting. Fiveto seven harvests at 4- to 5-d intervals may berequired to harvest the entire crop mechani-cally; therefore, it is desirable to breed forconcentrated maturity to reduce the numberof harvests. Breeding programs on brambles
Fig. 1. Commercialmodel of University ofArkansas cane fruitharvester, manufacturedand sold by BlueberryEquipment Co., Inc.,South Haven, Mich.
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at some land-grant institutions, at the USDA,and in Canada have developed cultivars oferect blackberries that adapt well to mechani-zation (Moore, 1979, 1984). These breedingprograms remain active and should continueto produce more cultivars better adapted tomechanical harvesting.
Most blackberry plantings need to berenovated after 5 or 6 years. Renovation can beaccomplished by mowing the entire hedgerowto 3 to 4 inches (8 to 10 cm) immediately afterthe final harvest. All mowed canes should beremoved from the field. A mechanical harvestercannot be used in the year following thisrenovation. However, the fruit from theseshorter vines can be hand harvested if an eco-nomical supply of labor is available.
The Pacific Northwest has adapted wellto mechanical harvesting of brambles. Grow-ers in Oregon machine harvest most of their1500 acres (600 ha) of black raspberries andmost of 8000 acres (2800 ha) of trailingblackberries and hybrid berries (Dale et al.,1995). The lack of rain in harvest season inthe Pacific Northwest makes mechanical har-vesting feasible. Where rainfall at harvest timeis common, harvest days are reduced, and thesofter fruit is more easily damaged, as are theprimocanes, which then easily succumb tocane death by the fungus Leptosphaeriacoriothyrium (Fckl.) Sacc. (Dale et al., 1995).
StrawberriesAt the University of Arkansas, several
harvesting principles had to be evaluated inthe process of developing a mechanical har-vester for strawberries since, historically, straw-berries have been considered one of the cropsleast adaptable to mechanization (Morris etal., 1978c; Nelson and Kattan, 1967; Nelsonet al., 1978).
HARVESTERS. A tractor-drawn prototypeof a mechanical strawberry harvester was de-veloped at the University of Arkansas in 1967,and since then it has undergone continualrevision (Fig. 2) including development intoa self-propelled machine. This prototype wasa stripping harvester. It used a reel withalternating brush and comb that rakedthrough the crop. Air suction lifted the ber-ries and foliage (Fig. 3). An airlock berryremoval system evacuated the debris whilethe berries dropped through the airlock valveonto the conveyor. A grower in Copemish,Mich., purchased this machine and suggestedthat it be built to accommodate two rows forbetter commercial acceptance. Subsequently,Blueberry Equipment Co., Inc. (BEI), ofMichigan modified and produced the Uni-versity of Arkansas harvester as a two-rowhydraulic-powered machine for commercialsale. In those early years, researchers workingwith the harvesters mentioned and othertypes of mechanical strawberry harvesters re-ported picking efficiencies from 31% to 87%(Denisen and Buchele, 1967), 91% to 97%(Morris et al., 1978c), and 24% to 92%(Booster et al., 1970a, 1970b; Booster, 1973.)
In addition to the University of Arkansasharvester, several others have been developedfor strawberries. Three different strippingtype machines were developed in Italy duringthis same period (Di Ciolo and Zoli, 1975;Lucignani, 1979; Rosati, 1980), and research-ers in Denmark produced a commercial ma-chine called the Danpluck harvester, whichuses 62-inch-wide (160-cm) rakes on a slop-ing belt to lift the berries. A unique finger reelplucks the leaves from the berries as an airejector expels them. (Thuesen, 1988).
Quick and Denison (1970) described astripping-type harvester that used a bank ofdiverging, vibrating ramps instead of a reel.Shikaze and Nyborg (1973) developed avariation on this design by replacing thevibrating action with a bank of small belts.However, there has been no commercial useof these machines. More recently, H. Lee ofthe University of Guelph, Canada, and BraggEnterprises in Canada have developed an-other version of the stripping harvester(Swinkles and Murray, 1991). Their machineuses a reel with cam-controlled finger barsthat work through the plants, stripping thestrawberries from their peduncles and dump-ing them through the cam mechanism onto aconveyor system.
The British National Institute of Agri-cultural Engineering developed a mower-type harvester that was modified by MichiganState University and then commercialized insomewhat different forms by two machinerycompanies, Smallford Planters of Silsoe, En-gland, and Conners Machinery, Inc. (CMI),
Fig. 2. First commercialsingle-row mechanicalstrawberry harvesterdeveloped by theUniversity of Arkansasand manufactured byBlueberry EquipmentCo., Inc., South Haven,Mich. A two-rowharvester was success-fully tested and usedcommercially inOregon.
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of Simcoe, Ontario,Canada (Hansen et al.,1983). The Smallford ma-chine used a cutter bar withfingers that lifted the ber-ries above the bar (Kemp,1976). The berries wereconveyed to a belt wherecutting blades clipped thetrusses, and debris wasblown back into the field.The CMI harvester em-ployed a more effective air-blast system to separate thedebris from the berries andused reciprocating clippersto cut berry trusses. Theheavy output of this har-vester led to the develop-ment of mechanisms thatwould support and alloweasy handling of shallowbulk bins and a suitablebox-filling system (Lauroand Hergert, 1987). Researchers in Arkansas(Booster, 1973), Oregon (Hecht, 1980) andGermany (Fiedler, 1987) developed similarharvesters, although the German machineused people seated on the harvester to sortand destem the fruit.
Research at the University of Arkansashas shown that certain strawberry cultivarsare more adapted to machine harvesting,cleaning, and sorting without loss of quality(Morris et al., 1978c, 1979c, 1980; Nelson etal., 1979). Quality of machine-harvested fruitfrom certain strawberry cultivars is improvedby prior handpicking (Morris et al., 1979c,1980). Once-over machine harvested straw-berries, after one or two hand harvests, havehad a higher percentage of ripe berries thanfruit machine harvested without a previoushand harvest. The percentage of total solublesolids, firmness, and color intensity of theonce-over harvested strawberries after one ortwo hand pickings was the same or higherthan that of hand-harvested fruit (Morris etal., 1980). Sensory quality of fruit puree fromboth machine-harvested and handpicked fruitwas rated as acceptable.
One of the most objectionable aspects ofmachine-harvested strawberries is the pres-ence of green, immature fruit. Many imma-ture berries can be separated from maturefruit in the processing plant, based on fruitsize. However, large green fruit that is sortedwith the large ripe fruit eventually ends up inthe processed product. Research has shownthat strawberry products made from cultivarscontaining high anthocyanin levels can toler-ate as much as 50% immature fruit in theproduction of commercially acceptable jam(Morris et al., 1979a; Sistrunk and Morris,
1978). Strawberry jam made from Cardinalstrawberries, which have extremely high an-thocyanin levels, can contain as much as 75%large immature fruit and still be rated accept-able (Spayd and Morris, 1981).
Strawberries are highly perishable. Re-search has shown that extremely firm-fruitedstrawberries for processing can be mechani-cally harvested, properly cleaned and handled,and then held for up to 48 h at 75 F (24 C)and up to 7 d at 35 F (1.7 C) withoutexcessive quality loss (Morris and Cawthon,1979). It also showed that fungicide dipsbefore storage suppress mold growth andreduce loss of soluble solids. An acetaldehydeatmosphere and a combination of atmospheresand dips are effective in maintaining goodcolor, freedom from browning and productacceptability of machine-harvested strawber-ries held for 72 h at 75 F (24 C) (Morris et al.,1979a, 1979c). However, these techniqueshave not been commercially implemented sinceit has never been practical to use machine-harvested fruit for the fresh market, and berriesare usually processed immediately.
Currently, only one strawberry harvesteris operating commercially in Oregon. Thisharvester was developed by the University ofArkansas and manufactured by BEI (Figs. 2and 3). The machine is used to strip themature fruit remaining after one or two handharvests. This fruit is being processed in apuree product. Improvement in strawberrycultivars that would make them better suitedfor once-over harvest or better suited formultiple harvest, or improvements in harvest-ing machines will be required before largescale mechanization of strawberries will beused.
Fig. 3. University ofArkansas mechanicalstrawberry harvester:(a) mowing sickle bar,(b) combbrush pickingand conveying system,(c) fan, (d) airlockvalve, and (e) fruittransporting conveyor.
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ery of cooler grapes, result in betterquality than grapes harvested in theheat of the day. Research has shownthat any type of grape harvested whenfruit temperature is high (86 F or 30C and above) will have poor color andproduce high levels of alcohol andacetic acid, both of which are signs ofmicrobial spoilage (Morris et al., 1972).The alcohol and acetic acid levels ofmechanically harvested grapes beginto rise after 12 h from the time ofharvest if grape temperature at harvestis as high as 85 F (29 C). Decreasesin soluble solids, flavor, and color qual-ity parallel the increases in alcohol andacetic acid (Benedict et al., 1968;Morris et al., 1979b). Off-flavors arepresent in the processed juice productwhen alcohol levels reach 0.05%. Thesestudies suggest that grapes producedin hot areas, such as the San JoaquinValley of California and the southernUnited States, should be harvestedduring cool periods of the day or atnight to minimize loss of quality(Benedict et al., 1968, 1973; Johnson,1977; Morris et al., 1979b.)
Adding sulfur dioxide (SO2) tomachine-harvested wine grapes mini-mizes quality loss during holding(Benedict et al., 1973; Bourne et al.,1963; Christensen et al., 1973; Morriset al., 1972, 1979b; OBrien andStuder, 1977). An applicator is com-mercially available that will meter aspray solution of SO2 onto the grapesbefore they enter the bins and is em-ployed principally on wine grapes. Ad-dition of 80 to 160 ppm SO2 immedi-ately after harvest has been shown toslow postharvest deterioration of ma-chine-harvested juice grapes by reduc-ing browning and delaying alcoholaccumulation and loss of soluble solidsfor 24 h (Morris et al., 1979b).
COLLECTION AND HANDLING. Me-chanical harvesters have two basic kindsof mechanisms for collecting the grapes:a belt system and a bucket system.Grapes that are juiced during harvest-ing are better handled with the bucketsystem. However, the bow rod pickinghead harvests more intact fruit causingless juicing than the fiberglass rods ofthe pivotal striker head.
The initial containers used forhauling Concords and other juicegrapes to the processing unit were 1ton (0.9 t) capacity wooden bins withfood-grade plastic liners. Many opera-tions have switched to the west coastmethod, where a 4 to 5 ton (3.6 to 4.5
Major developments in juice andwine grape harvest mechanization oc-curred in the early and mid-1960s(Olmo, 1980; Shepardson and Miller,1962; Shepardson et al., 1969; Studerand Olmo, 1969), and mechanizationwas practiced commercially by the late1960s (Johnson, 1977; Marshall et al.,1972). Mechanically harvested grapescan have better quality than hand-harvested grapes when deliveredpromptly to the processing unit(Whittenberger et al., 1971). Trellis-ing systems suited for mechanical har-vesting and other mechanical opera-tions continue to be a major prerequi-site to successful harvesting of grapes.
HARVESTERS. Basically, there aretwo configurations of mechanical har-vesters, tractor drawn and self pro-pelled. Cattell (1994) reported thatthe towed models cost between$40,000 and $75,000. These unitscan generally be justified when theprice of hand harvesting is between$8,000 to $10,000 a year. These towedunits can easily handle 120 acres (48.6ha) per season. Often, the overridingfactor in a decision to purchase a har-vester is to have total control overwhen grapes are harvested.
The self-propelled machinesstraddle the row and cost between$120,000 and $150,000. They canharvest over 247 acres (100 ha) in thecourse of a season. Grape growers withmore than 100 acres (40.5 ha) usuallyconsider the self-propelled units. Sincethese units have a larger capacity, somegrowers do custom harvesting as a sideline. In the large grape-producing ar-
Fig. 4. Bow rods inserted horizontally inthe picking field.
eas of California, some companies donothing but custom grape harvesting.These companies use only the over-the-row harvesters. These harvesterscan be converted to harvest either asingle-wire trellis or a divided double-curtain trellis, which contains two sepa-rate foliage canopies.
Many of the commercial harvest-ers use pivotal strikers, arranged as adouble bank of flexible horizontal rods,that strike and shake the vine to re-move fruit. They can be operated as inphase or out of phase. In phase meansboth the front and rear strikers move inthe same direction at the same time.This can cause vibrations, which needto be balanced by counter weights.Vibrations are not a problem with theout-of-phase pivotal strikers (the typeon most older models). However, de-pending on the vine growth, they maynot pick as well. Conversion kits arereadily available to convert the out-of-phase to an in-phase system.
Another principle used in Califor-nia is the trunk shaker in which twoparallel rails impart horizontal vibra-tion to the upper trunk and/or cor-don. The trunk shaker is most effectivein removing fruit located close to arigid trunk or cordon, and much lessmaterial other than grapes, such asbark, canes, leaves, and petioles, isharvested compared to that with thepivotal striker. Some machines havecombined the two principles and re-duced the number of horizontal rods.
Another picking head is the bowhead or bow rod unit. Constructionmay vary from manufacturer to manu-facturer, but the shaking elements areround commercial plastic bar stock 1to 1.5 inches (2.5 to 3.8 cm) in diam-eter and 5 ft (1.5 m) long having thegeneral shape of a closed shepherdsstaff (Fig. 4). These horizontally ori-ented bars move transversely and shakethe vine. The shaking action on theleaves is more gentle than with pivotalstriker rods, and the longer strikingdistance results in less defoliation. Thebow head also allows for greater har-vesting speed. Because of the intro-duction of the bow head, the trunkshaker is not as popular in Californiavineyards as it was in the 1980s.
GRAPE QUALITY. The mechanicalharvester makes it possible to harvestat night and the advantages of nightharvesting cannot be over emphasized.Grapes harvested at night when tem-peratures are more favorable for deliv-
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t) capacity, hydraulic, self-dumpingvineyard gondola is used to transferharvested wine or juice grapes intoopen-top, bulk tank trucks.
GUIDELINES FOR EFFICIENT MECHANI-CAL HARVESTING. Researchers at the Uni-versity of Arkansas in cooperation withcommercial grape growers have devel-oped guidelines for efficient mecha-nized harvesting and handling: 1) Se-lect the proper revolutions per min(rpm) of the shaking mechanisms orstrikers and the proper ground speedfor each cultivar and crop load situa-tion. 2) Establish a time limitation foreach cultivar from harvesting to pro-cessing plant delivery. 3) Optimize fruittemperature and SO2 usage. 4) Elimi-nate problems of material other thangrapes (MOG). 5) Cease cultivationsufficiently before harvest to minimizedusty conditions. 6) Inspect the vine-yard for foliar-feeding insects and, ifnecessary, apply sprays sufficientlyahead of harvest. 7) Provide a bin orconveyor inspector as part of the har-vesting crew to remove MOG, to watchfor plugging of cleaning fans, hydrau-lic leaks and mechanical failures, and tomonitor SO2 application. 8) Cover har-vested grapes at all times and clean thebin after each dumping. 9) Clean me-chanical harvesters thoroughly with ap-proved detergent and sanitizer asneeded. 10) Install a magnet on themachines discharge conveyor to col-lect staples and other iron-containingobjects. These guidelines were devel-oped for commercial harvesting of Vi-tis labruscana L. in the eastern UnitedStates. Similar guidelines have been orshould be developed for each regiondepending on standards established bythe processors.
Specialty grapesMUSCADINE GRAPES. Muscadines,
Vitis rotundifolia Michx., are used pri-marily for wine, and most of thesemuscadine wine grapes are machineharvested. Muscadines are also soldfresh and as juice, jams, and jelly. Mus-cadine grapes present a challenge formechanical harvesting since they growin small clusters that usually contain 6to 24 large berries. Mature berries ofmost muscadine cultivars do not ad-here to their pedicel as do those of thebunch grapes. This makes muscadineseasy to remove, but can cause theproblem of fruit dropping in advanceof the mechanical harvester. To pre-vent the loss of this over-mature fruit,
an extended collecting unit has beendesigned that is adaptable to the frontof any conventional commercial har-vester (Morris, 1994). When usingthe over-the-row mechanical harvest-ers that have four sets of beater rods,the front two sets can be removed.This allows the beating action to startafter the fruit to be removed has com-pletely entered the harvester.
Machine-harvested muscadinesmay be sorted effectively according totheir density, with the denser berriesfalling into the riper categories (Lanierand Morris, 1979). Density sorting isa rapid and inexpensive method ofremoving fruit of undesirable matu-rity. In the 1980s, when North Caro-lina had a significant commercial mus-cadine grape industry, one grower builtand successfully used this density sepa-ration system. However, today thesystem is used primarily by scientists toevaluate cultivars and cultural systemsfor their suitability for once-over har-vesting from the standpoint of uni-form maturation.
RAISINS. Mechanization of raisinharvest has been more difficult thanthat for other grapes. A severed-caneor harvest-pruning technique to facili-tate the mechanical harvesting of Th-ompson Seedless raisin grapes wasreported by Studer and Olmo (1971,1974). Cutting the fruiting cane nearthe base and leaving the fruit on thetrellis wires for 4 to 8 d until thepedicels dry allows the grapes to beharvested as single berries by any typeof vibrating harvester. The individualberries are conveyed into a hopper andthen metered and spread evenly on acontinuous paper strip. The singleberries will dry uniformly without be-ing turned. The dried raisins are pickedup by another machine, with metalfingers that run under the paper stripto guide it to revolving brushes, whichsweep the raisins onto conveyors thattransport them into bulk bins.
Dried-on-the-vine (DOV) raisinproduction research began in Austra-lia in the late 1950s and early 1960s(May and Kerridge, 1967). Parallelefforts were under way in Californiawhere the method was used on BlackCorinth and Thompson Seedlesscultivars. The efforts on DOV Zantecurrants (from Black Corinth grapes)were successful (Christensen et al.,1970), but the results with Thomp-son Seedless, the primary raisin grape,were disappointing due to their later
maturity, higher vigor, and larger berrysize (Studer and Olmo, 1973). Har-vest-pruned Thompson Seedlessgrapes dried to 25% to 35% moistureafter 6 to 9 weeks of vine drying ontheir standard trellis systems. Attemptsto speed up the DOV process includedoleate sprays (Petrucci et al., 1974),but as in Australia, adequate emulsionspray coverage was difficult to achieve,and the final product was differentfrom the natural Thompson Seedlessraisin (Striegler et al., 1996). The DOVThompson Seedless raisin sprayedwith oleate was not embraced by theconsumer. In 1984, the raisin industryenthusiastically embraced the sprayed-on-the-tray (SOT) method of raisinproduction after shallow consumertesting. That year the industry pro-duced 7,745 tons (7,048 t) of SOTraisins, only to have that productionfall to 38 tons (34.6 t) in 1988, be-cause consumers did not buy them.Producers were anxious not to repeatthis mistake (Malcolm, 1993).
Although the concept of DOVraisins is an old one, DOV has beengiven new life through research devel-opments. In the new DOV method,raisins are not sprayed with oil. Newtrellising systems and newly introducedseedless grape cultivars have made thespraying step unnecessary. Tradition-ally, in California, raisins are harvestedin September and boxed 12 to 21 dlater, depending on drying conditions.With the present DOV system, canesare cut in August so the chance of rainis very low.
New trellis systems have been de-veloped for DOV production. Thesetrellis systems follow the general prin-ciple of separating the vine canopy intofruiting and nonfruiting zones and aredesigned also to facilitate mechaniza-tion of harvest pruning, the cutting offruiting canes for drying on the vine.Generally, this years canes are on thesouth side of an eastwest row andnext years canes are in a catchingtrellis system that provide for maxi-mum sun exposure. The southern ex-posure gives adequate sunlight expo-sure and optimum drying conditions.Australia is also actively reviving theDOV system. They have introducedspecialized trellising systems along theabove described lines: the Irymple sys-tem (Gould and Whiting, 1987), theShaw system (Shaw, 1986), and theswing-arm system (Clingeleffer andMay, 1981).
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Another manner in which to improvethe DOV system is to use specially designedseedless cultivars. Three cultivars are beinginvestigated for use in DOV raisin produc-tion. Thompson Seedless 2A is a heat-treated,virus-free clone of Thompson Seedless. Ithas a proven track record of productivity andis preferred for new plantings of ThompsonSeedless for raisins and crushing. Fiesta is aresult of a complex cross made in the 1960sat the USDA Horticultural Field Station inFresno, Calif. It ripens 10 to 14 d earlier thanThompson Seedless, produces high qualityraisins and, after initial concerns over seedtraces were laid to rest, has gained supportersin the last several years [3,840 acres (9,489ha) in 1996] (Christensen, 1997). DOVineis a recent (1995) release by David Ramming(USDA) as an early ripening (2 to 3 weeksbefore Thompson Seedless) cultivar that issuitable for DOV production (Christensen,1997). DOVines high vigor provides po-tential for a large vine framework and a canopyadapted to more expansive trellising and thedemands of cane renewal for DOV. In fact, itsgreatest potential is with large, expansiveDOV trellis systems where the canopy can bespread. Vigor control through controlled dripirrigation and nitrogen fertilization will benecessary in most sites. Vertical or south sidesystems may not handle the vigor unless thesecontrol measures are taken.
All three of these cultivars show ap-propriate fruitfulness characteristics forDOV. In comparative studies done at theCalifornia Kearney Agricultural Researchand Extension Center, raisin yields werestatistically similar among the cultivars.Berry weights were heaviest with Fiesta,followed by DOVine and Thompson Seed-less 2A. Airstream sorter raisin grades weresimilar, except the percentage of substan-dard berries was higher in DOVine thanin Thompson Seedless 2A. Researchers con-cluded that Thompson Seedless (the 2Aclone) will continue to be a dominant culti-var because of its adaptability, versatility,
familiarity, and longevity (Christensen, 1997).Industry leaders believe the DOV tech-
nique has potential for saving money whileimproving their operation and producinghigh-quality raisins. The new DOV systemseliminate pickers, turners, rollers, the tradi-tional boxing crew, and even paper trays.There will be savings in crop insurance as it ispresently written and on workers compensa-tion. Estimates of savings run as high as$300/acre (2.5 ha) with DOV production(Malcolm, 1993).
In 1992, one prototype harvester forDOV production was designed and manufac-tured by Ag Right Enterprises of Madera,Calif. The unit is operated by hydraulics anduses a radial-forced balanced shaker unit thatgently knocks the raisins off the canes into acatcher with a conveyor belt that takes it up toanother conveyor unit that deposits the rai-sins into a bin trailer running in the adjacentrow, parallel to the machine. Another proto-type harvester system that is currently beingevaluated is manufactured by Korvan Indus-tries, Inc., Ore.
More time is needed to evaluate themost cost effective trellis systems, handling,and processing. However, industry is con-cerned about market analyses and the publicsacceptance of the characteristics of DOVraisins. In 1993, one raisin board adopted along-term policy of gradual market develop-ment (Malcolm, 1993).
Other mechanization practicesfor grapes
PRUNING AND THINNING. Along with me-chanical harvesting, other mechanized pro-cesses can improve efficiency in grape pro-duction. Mechanical pruning can reduce handlabor by as much as 50%. Studies in Arkansason shoot-positioned Concord grapevinestrained to Geneva Double Curtain (GDC), (asystem with two adjacent wires 4 ft (123 cm)apart with vines trained on them to form adouble curtain of foliage) or bilateral cordonsystems (which have one wire with vine cor-dons running up and down forming a singlecurtain of foliage) examined the effects ofmechanical pruning on yield, vine size, andjuice quality. The results showed that con-tinual mechanical pruning of Concord grapesis recommended only in shoot-positionedvineyards where cane selection and adequatenode, shoot or fruit limitation follows prun-ing. Recent data from the author show thatmechanical fruit thinning also eliminates theproblem of overcropping without the needfor hand thinning. Data collected in a com-mercial vineyard in New York in 1997 showedthat it was possible to mechanically thin amachine-pruned vineyard with the Morris-
Table 1. Effect of thinning double curtain Concord grapes grown atMerritt Vineyard, N.Y, 1997. Source: Joint research by Morris, Main, andDunst funded by New York State Agricultural Experiment Station Viticul-ture Consortium Research Grants Program.
Soluble RedYield solids pigment
Treatment (tons/acre) (%) pH (520 nm)
Control 13.5 az 12.7 c 3.24 4.04 cC-Ry 250 rpm 9.9 bc 14.2 b 3.27 6.01 bM-Ox 200 rpm 11.5 ab 13.7 b 3.28 4.71 bcM-O 225 rpm 11.0 bc 14.4 b 3.27 6.08 bM-O 250 rpm 9.2 c 15.2 a 3.25 8.15 azMeans within the same column having the same letters are not significantly different at 0.05.yChisholm-Ryder harvester for thinning.xMorris-Oldridge thinning unit.
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Oldridge thinning unit at 250 rpm and ob-tain high quality (15.2% soluble solids) Con-cord juice grapes (Table 1).
SHOOT POSITIONING. Shoot positioningallows for effective mechanical pruning. Shootpositioning of the canes to avoid shadingexposes the lower nodes on the bearing unitsto sunlight, making these basal nodes moreproductive, and improving fruit quality (Mor-ris et al., 1984). Positioning is particularlyeffective on the vigorous V. labruscana culti-vars. Vines are usually shoot positioned forthe first time at first bloom, but completeshoot positioning usually requires a secondand possibly a third pass (Fig. 5). A properlyshoot-positioned GDC system with two sepa-rate foliage canopies is more efficient to har-vest mechanically than a nonpositionedcanopy. A bilateral or single-curtain systemthat has been shoot positioned is easier tomechanically prune and mechanically harvest
with less damageto fruit and canes.
COMPLETELYMECHANIZED SYS-TEMS FOR GRAPES.In a cooperativeresearch effort theauthor and TomOldridge, grapegrower and inven-tor from Lowell,Ark, have devel-oped systems forvineyard mechani-zation, and wehave a pendingpatent on vineyardmachinery andsystems. The Mor-ris-Oldridge Sys-
tems provide machines that allow for almostcomplete mechanization of all vineyard opera-tions. The patent describes a method for com-plete vineyard mechanization of 12 differenttrellising systems and methods to modify,trellis, and train grapevines. These develop-ments eliminate expensive hand operations,and production can be economically mecha-nized without any substantial loss of yield orfruit quality. This patent is the result ofstudies at the University of Arkansas over thelast 32 years that have involved the evaluationof trellising and training systems suitable forcomplete vineyard mechanization, mechani-cal shoot positioning, mechanical pruning,mechanical thinning (Tables 1 and 2), me-chanical harvesting, and the postharvest han-dling and use of mechanically harvested grapes(Cawthon and Morris, 1977; Morris, 1985;Morris and Cawthon, 1980a, 1980b, 1981;Morris et al., 1975, 1984).
Currently, two trellising systems can becompletely mechanizedthe GDC and thesingle curtain system. In addition, variationsof these systems can also be completely mecha-nized. We have designed a complete mecha-nization system with the apparatus and meth-ods for the mechanization of, not only thejuice grapes of Vitis labruscana species, but
Table 2. Effect of thinning and pruning methods on yield and fruit quality of Cabernet Sauvignon grapes grown at VinoFarms, Inc., Lodi, Calif., 1997.
Soluble TartaricPruning Thinning Yield solids acid Anthocyanintreatment treatment (tons/acre) (%) pH (%) (mg/cm3)
Spur pruned control None 11.4 bz 25.2 bcd 3.78 0.54 abc 0.30 bcMachine None 15.0 a 23.7 de 3.60 0.57 a 0.31 bcMachine M-Oy (400 rpm) 8.5 c 26.6 ab 3.72 0.51 bc 0.39 abMinimal None 15.2 a 22.4 e 3.52 0.59 a 0.26 cMinimal M-O (600 rpm) 10.8 bc 25.2 bcd 3.63 0.55 ab 0.37 abzMeans within the same column having the same letters are not significantly different at 0.05.yMorris-Oldridge thinning unit.
Fig. 5. A Geneva double curtain over-the-row mechanical shoot positioner developedby Tom Oldridge, Lowell, Ark. Addingcutter bars behind converts the machine to amechanical pruner. These units are used aspart of one of the 12 Morris-Oldridgevineyard mechanization systems.
30 JanuaryMarch 1999 9(1)
also Vitis vinifera L. and FrenchAmerican hybrids (Vitis interspecieshybrids). The FrenchAmerican hy-brids are interspecific hybrids that varya great deal in their vine characteris-tics. Almost all hybrids tend to beextremely fruitful. This fruitfulness isdue primarily to the high number ofclusters per node and the extremelyfruitful basal nodes. These basal nodesare seldom, if ever, fruitful with V.labruscana and V. vinifera species.
Hand thinning of FrenchAmeri-can hybrid vineyards is conducted inthe traditional manner to ensure asustainable fruit load that producesconsistently high quality fruit fromthese cultivars. However, hand thin-ning is expensive and one of the great-est challenges in producing these cul-tivars. Mechanical thinning is botheconomical and successful on thesehybrids. Mechanical removal of basalleaves in V. vinifera has successfullyreduced fruit rot (Table 3) from 26.5%to 16.1% on Chardonnay grapes atSanta Maria, Calif., in 1997. Removalof leaves by hand did not significantlyreduce rot over machine removal, andthe cost of hand removal was esti-mated at $120/ acre (2.5 ha).
Most premium wines producedin the world comes from V. viniferagrapes. Wineries pay premium pricesfor high quality vinifera grapes. Insome regions, the crop must be lim-ited, and leaf removal is practiced toproduce a specific quality, and in oth-ers, the crop must be limited to ensurematurity due to a shortened growingseason. Also, crop adjustment is usedin many grape regions of the world andis even enforced by law in some. Theseare expensive operations when carriedout with hand labor. By mechanizingthese operations, grape production forpremium wine production should be-come more profitable.
In brambles and strawberries aswell as grapes, mechanization can im-prove efficiency, but wise use of suchmechanization requires careful adap-tations to specific crops and some-times to specific cultivars. For example,although complete vineyard mechani-zation systems and methods providethe viticulturist with a wide array oftools, careful use and intelligent imple-mentation of each of these tools mustbe understood for the systems to besuccessful. Further research and con-tinued improvement in mechanizedpractices will make completely mecha-nized systems more efficient. Adop-tion of completely mechanized sys-tems can potentially mean more reli-able, more stable and more economi-cal production of premium quality fruitthat will be competitive for the local,regional, national and global markets.
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Booster, D.E. 1973. The mowing method ofharvesting strawberries. Amer. Soc. Agr. Eng.Paper 73-109.
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Table 3. Effect of leaf removal method on rot, yield, and quality of Chardonnaygrapes grown at White Hills Vineyard, Santa Maria, Calif, 1997. Source: Strieglerand Berg, Viticulture Enology Research Center, California State University,Fresno.
Soluble TartaricRot Yield solids acid
Treatment (%) (tons/acre) (%) pH (%)
No Leaf Removal 26.5 az 4.4 23.3 3.51 0.85Hand Removal 10.6 b 5.7 22.8 3.52 0.77M-Oy no hand followup 12.4 b 5.5 23.3 3.56 0.79M-O hand followup 16.1 b 5.4 23.7 3.52 0.92zMeans within the same column having the same letters are not significantly different at 0.05.yMorris-Oldridge thinning unit.
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Lanier, M.R. and J.R. Morris. 1979. Evaluationof density separation for defining fruit maturitiesand maturation rates of once-over harvested mus-cadine grapes. J. Amer. Soc. Hort. Sci. 104:249252.
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