There has been a revolution in recent years in the area of small fruit and grape harvesting. Hand labor has become both scarce and costly, thus invention and development of mechanical harvesters have become important research objectives for research scientists in Land-Grant Institutions, in the U.S. Department of Agriculture (USDA), and in private industry.
Spray application of 2-chloroethylphosphonic acid (ethephon) to walnut trees caused dehiscence of hulls and enabled complete nut removal with a single mechanical shaking operation as much as 3 weeks earlier than normal. Walnuts were hullable and the quality was generally superior to that of the controls. In some instances considerable leaf fall resulted from the treatment.
Yield of process fruits from ‘VF-145’ tomato plants grown in twin rows on 5-ft beds was greater than from plants in single rows on 4.5-ft beds. The number of fruits per plant increased as the area per plant increased beyond 2.1 ft2, but the mean weight per individual fruit was not affected. The highest number of process fruits per plant was produced by single plants spaced at 48 inches. Plant densities ranged from 2,450 to 158,816 plants per acre. Significant increases in yield were obtained by increasing the plant density from 2,450 to 9,801 plants per acre. Plants grown at densities of 19,602 to 156,816 plants produced from 36 to 42.5 tons of process tomatoes per acre.
An array of 102 single and 3-way cross hybrids of pickling cucumbers (Cucumis sativus L.) were evaluated for yield over 2 years under field conditions. Hybrids were produced by crossing lines with gynoecious, monoecious, hermaphroditic, and androecious expression. The significant correlations between femaleness (percent pistillate nodes) and marketable yield were 0.34 for single cross and 0.45 for 3-way cross hybrids. Highest yields were obtained from the single crosses of gynoecious × androecious, and gynoecious × hermaphrodite, followed by the 3-way cross of (gynoecious × hermaphrodite) × androecious, on the basis of either total or marketable fruits per plant. Hybrids having androecious pollen parents exhibited more femaleness and produced higher yields than those with monoecious pollen parents. The possible use of these high yielding parental sex combinations as hybrid cultivars in place of conventional single crosses (gynoecious × monoecious) might improve the production of pickling cucumbers for once-over mechanical harvest.
Two field experiments were conducted in Bet Hashita (1992) and Newe Ya'ar (1993), Israel, in order to examine the possibility of using plant growth habit, chlorflurenol, and plant population density to concentrate yield of pickling cucumber (Cucumis sativus L.) under a simulated once-over mechanical harvest system. Two near-isogenic cucumber lines, WI 1983G normal and WI 1983G little leaf, were grown under three plant densities, 5, 10, and 20 plants/m2, and at flowering half of the plants were treated with 50 mg·L-1 chlorflurenol solution. The little leaf line produced a smaller canopy than the normal line under five plants/m2 but a larger canopy under 20 plants/m2. The average commercial yield of the little leaf line was higher than that of the normal leaf line by 28% and 55% in Bet Hashita and in Newe Ya'ar, respectively. The highest yield of each line was achieved under the highest plant density. The average commercial yields under 20 plants/m2 were 1.13 and 0.91 kg·m-2 in Bet Hashita and 1.86 and 0.92 kg·m-2 in Newe Ya'ar for little leaf and normal leaf, respectively. Chlorflurenol increased fruit number per unit area but did not increase yield. Nevertheless, it increased the proportion of small fruits, which are more valuable. The present study shows that the little leaf growth habit can increase the yield concentration in pickling cucumber and make this crop more suitable for a once-over mechanical harvest. Chemical name used: methyl-2-chloro-9-hydroxyfluorene-9-carboxylate (chlorflurenol).
Nontreated seed, primed seed, and transplants were compared for effects on stand establishment, plant morphology, and yield of paprika pepper (Capsicum annuum L.). Nontreated seed was satisfactory for stand establishment, although primed seed had the potential to provide greater initial stands. When populations were made equal by thinning, there were few differences in stem and leaf dry weight, fruit yield, or plant morphology attributed to seed treatment. Generally, morphology of plants established by direct seeding was favorable for mechanical harvest. Using transplants did not result in higher marketable fruit yields than direct seeding in 2 of 3 years. When compared to plants established by direct seeding, three trends were consistent across all 3 years for plants established by transplanting: 1) they were more massive, 2) they had larger vertical fruiting planes, and 3) they had more branches. These traits increase the difficulty of mechanical harvest and create the potential for more leaves and stems (trash) in the harvested product. Thus, transplanting is not recommended for stand establishment of paprika pepper intended for mechanical harvest.
Broccoli (Brassica oleracea L. Italica Group) lines with heads borne above the foliage (exserted) favorably for mechanical harvest were crossed with inbred lines with nonexserted heads. Length of the heads, defined as the portion of the plant above the highest major leaf, was ≈50% of the total plant height in short and tall parents and all plants of the F1, F2, and backcross generations. The principal characteristic identified with good head exsertion was long internodes. Internode length was inherited mostly in an additive manner, with some effect of hybrid vigor apparent in the F1, F2, and backcross to the tall parent. Plant height was also inherited in an additive manner. Head weight in the high-exsertion parent was much lower than in the low-exsertion parent. Within each parent and the F1, head weight was greater in plants with longer internodes and greater plant height. In the segregating generations (F2 and backcross), head weight increased with decreasing internode length, indicating that selection for high head exsertion would result in smaller heads and reduced yield.
Mechanical harvest of paprika pepper (Capsicum annuum L.) produces a mixture of marketable and unmarketable fruit. Our objective was to increase the percentage of marketable red fruit in a once-over harvest by using ethephon to remove late-developing flower buds, blooms, and green fruit. Three experiments were conducted on field-grown plants in southwestern Oklahoma. We tested ethephon solutions of 0, 1000, 2000, 3000, and 4000 μL·L-1 as a one-time foliar application on various dates in September and October. Total dry mass of harvested fruit decreased linearly as ethephon rate increased in all experiments. Marketable fruit, as a percentage of total harvested fruit mass, increased linearly with ethephon rate in two of three experiments. Ethephon decreased the percent of total harvested fruit mass due to green fruit in all experiments. We recommend a single application of ethephon at about 2000 to 3000 μL·L-1 as a controlled abscission agent to increase the percentage of harvested red fruit in paprika pepper. The precise timing of the application will vary with the situation, but the last 10 days in September seemed an appropriate interval for southwestern Oklahoma. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).
occurred; ‘Duke’, ‘Reveille’, and ‘Cara’s Choice’ were able to ripen and retain firmness on the bush. However, a concentrated ripening period was more desirable for mechanicalharvest than extended holding ability, as an extended holding ability tended to
Methyl jasmonate (MJ) was tested as a potential abscission chemical to enhance mechanical harvest of `Hamlin' and `Valenica' orange [Citrus sinensis (L.) Osb.]. In field experiments, a solution of 1, 5, 10, 20, or 100 mm MJ was applied either as a stem wrap to individual fruit or as a spray to entire trees or canopy sectors. Solutions of 10, 20, and 100 mm MJ resulted in significant and consistent reduction of fruit detachment force and caused fruit drop within 7 to 10 days. Fruit loosening was preceded by an increase in the internal ethylene concentration of fruit similar to that of other experimental abscission compounds. While concentrations of 10 mm and less caused no or negligible phytotoxicity, solutions exceeding 10 mm MJ induced unacceptable levels of leaf abscission.