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- Author or Editor: D.L. Peterson x
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.
An irrigation control valve that uses the suction developed in a tensiometer to start and stop the flow of water to the irrigation system without the need of electricity was constructed. When soil water suction reached –22 cbars at 25 cm, the valve opened and then closed at –18 cbars. Peach trees at 6 × 6 m (three trees per plot) or 4.9 × 3 m (five trees per plot) spacing were irrigated with either pulse microsprinkler or drip irrigation. Evapotranspiration (ET) was calculated from pan evaporation and adjusted for each plot, based on canopy diameter. Flow meters measured water use for each plot in a split plot design with six replications. In Sept. 1995, drip ET was 30%, and pulse ET was 200% of calculated ET for both plant spacings. Spatial variability in actual and calculated plot ET was >200%, and actual plot ET was highly correlated with calculated plot ET. Data for the 1996 field season will be presented. The results indicate that spatial variability in water use is high, and the tensiometer valve is effective and reliable in scheduling irrigation in a heterogeneous environment.
Three years of mechanical harvesting (shake and catch) trials with two freestanding apple (Malus domestica Borkh.) cultivars on a semidwarf rootstock (M.7a) and two training systems (central leader and open center) yielded 64% to 77% overall harvesting efficiency. Mechanically harvested `Bisbee Delicious' apples averaged 70% Extra Fancy and 10% Fancy grade, while two `Golden Delicious' strains (`Smoothee' and `Frazier Goldspur') averaged 40% Extra Fancy and 13% Fancy grade fruit. Mechanically harvesting fresh-market-quality apples from semidwarf freestanding trees was difficult and its potential limited. Cumulative yield of open-center trees was less than that of central-leader trees during the 3 years (sixth through eighth leaf) of our study. `Golden Delicious' trees generally produced higher yields than `Delicious' trees.
This study evaluated the total and marketable yield of three peach cultivars [Prunus persica (L.) Batsch. `Autumnglo', `Harvester', and `Redhaven'] when mechanical pruning and harvesting systems were used and trees were grown under three irrigation regimes. All cultivars were trunk-shaken using an experimental inertial shaker on an over-the-row (OTR) shake–catch harvester. `Autumnglo' also was hand-harvested at all irrigation regimes. Fruit damage was not significantly affected by irrigation. A significant source of fruit damage was pruning debris that remained in the canopy after hedging and became lodged in the fruit-conveying system, resulting in cultivar effects on fruit damage. Total yield of firm-ripe fruit was similar among cultivars in 1987 and 1988. However, `Autumnglo' trees had a higher percentage of marketable fruit than `Redhaven' or `Harvester' in 1987 and 1991. Mechanical harvesting appeared to accelerate the decline of `Autumnglo' as shown by tree deaths and greater symptom expression of Prunus necrotic ringspot virus. The potential for a single mechanical harvest of peaches is limited because of the difficulty in managing the ripening window, the high potential for fruit damage, and the possibility of accelerated tree decline for disease-susceptible cultivars.
The objectives of this lysimeter study were to 1) evaluate the amount of dewfall, 2) determine the contribution of dew to daily evapotranspiration (ET) in fall-grown strawberries (Fragaria ×ananassa Duch.), and 3) determine the relationship between actual and potential ET (PET) of strawberry. Dewfall amounts averaged 0.8 mm·day–1 and accounted for 33% of the daily ET during the 27 Sept. to 6 Nov. period. Daily ET was linearly related to PET calculated from the Penman–Monteith equation, with an accuracy of ±3 mm based on lysimeter ET. Daily ET for 2- to 4-day periods was estimated with an accuracy of ±1 mm using the Penman–Monteith. We conclude that dewfall cannot be ignored in the ET of fall-grown strawberries in the mid-Atlantic section of the United States.
The purpose of this study was to determine if over-the-row mechanical shake-catch harvesting affected root development, leaf water stress, and yield of young ‘Golden Delicious’/M.7A and ‘Law Rome’/MM.111 apple (Malus domestica Borkh.) trees. Leaf water potential and temperature differential (canopy-air temperatures) were not significantly altered by mechanical harvesting. A minirhizotron technique did not detect changes in root distribution or root morphology. The fruit yield was unaffected by mechanical harvesting for four harvest years. No deleterious effects were detected as a result of over-the-row shake-catch harvesting.
Hand-thinning (Prunus persica L. Batsch) “Y”-trained peach trees at bloom and 51 days after full bloom (DAFB) was compared to mechanical fruit thinning 51 DAFB using a spiked-drum and an impact shaker. The spiked-drum shaker removed more fruit from horizontal branches than from vertical branches, yet did not selectively remove either large or small fruit. Bloom thinning by hand increased fruit size compared to postbloom thinning 51 DAFB, and both postbloom mechanical thinning techniques were as effective as postbloom hand thinning. The spiked-drum shaker may be a better thinning technique than the impact shaker because it transfers less shaking energy to the fruit, can be used in high-density plantings, and does not contact the trunk, lessening the potential for tree damage.
Six cultivars and three advanced breeding selections of fresh-market peaches (Prunus persica Batsch.) were evaluated for once-over mechanical harvesting. Factors evaluated were uniformity of maturity, fruit size, and incidence of damage in firm-ripe fruit. Harvest date was determined by estimating visually when equal amounts of green and over-ripe fruits were on the tree. In practice this criterion was difficult to achieve. Only on two occasions during the 2-year test did the proportion of firm-ripe fruit exceed 80% of total harvested fruit. Mean incidence of damage due to mechanical harvesting ranged between ≍2% and 12%. Nonuniformity of maturity of fruit on a given tree is a major hindrance to once-over harvesting of peaches.
‘Idlewild’ peach [Prunus persica (L.) Batsch] was released by the Louisiana Agricultural Experiment Station to provide a 500- to 600-hr chilling-requirement cultivar which produces a good quality fruit. ‘Idlewild’ produces a heavy crop of medium to large semi-freestone fruit that ripen 36 days before ‘Elberta’ or about June 9 in southeastern Louisiana. ‘Idlewild’ has exhibited good resistance to bacterial leaf spot [Xanthomonas campestris pv. pruni (Smith 1903) Dye 1978] when grown under southeastern Louisiana conditions.