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U.S. crop loss from hail damage amounted to $246,443,391 in 1991. Premiums paid for hail insurance was $403,742,507. Despite the magnitude of this industry, the effects of varying levels of hail injury at different stages of plant growth is largely unknown for many vegetable crops. To further evaluate the effects of hail on strawberries, watermelons, and sweet corn, several studies were established in 1991 and 1992. Simulated hail applications were made at different rates and stages of crop growth. Total yields and marketable yields of strawberries were reduced by hail applications. All hail treatments reduced the number of marketable watermelons, except for the vegetative size light hail treatment in 1991. In 1992, the early treatments caused the most total yield reduction. All hail treatments reduced the percentage of marketable ears of sweet corn, except for the light application in the 13th leaf stage (early vegetative) in 1991. In 1992, additional treatments consisting of clipping all leaves were conducted. Clipping leaves at the early silking stage reduced marketable ears, indicating the loss of foliage adversely affected the growth of the ear. Clipping leaves just prior to harvest reduced the yield of Jubilee, but not Silver Queen.
Mechanical pod strippers are the predominant method of harvesting lima beans (Phaseolus lunatus L.) for processing. Field losses are high, averaging 20% of potential yield in over 90 tests conducted in commercial fields. The three most significant factors that affect lima bean recovery are the field levelness, the relationship between ground speed and picking reel speed, and the lima bean variety. Further study on the relationship between pod location of four lima bean cultivars and the recovery of lima beans harvested with pod stripper combines was conducted in commercial fields. Pod location was categorized into three distinct zones of the plant. These three zones represented pods falling below the point the mainstem comes out of the ground, the first 5 cm from that point up the main stem, and all other pods higher than 5 cm above the stem. Differences in four cultivar's habits of setting pods in the three zones were established. `M-15' placed more pods in the lower zones than other cultivars. `M-15' also exhibited consistently more harvest loss than other cultivars when harvested with pod stripper combines. Other cultivars set pods higher in the plant and exhibited less harvest loss. With the harvest loss and pod set data, a rating procedure for the harvestability of lima beans was explored. While several potential rating systems demonstrated strong correlation with harvest loss data, a simple rating based on the percentage of pods in the canopy of the plant had the highest correlation coefficient (r = 0.96) with harvest loss. New cultivars can be evaluated for their harvestability characteristics using this rating system.
Production and harvesting systems for processing vegetables have been highly mechanized, however, field efficiencies are generally low, and high field losses and fruit damage continue to limit profits for several crops. By comparison, the number of fresh market crops currently machine harvested is small, and research to develop new harvesting technology for these crops is limited. Current mechanization research includes improvements to existing production systems, development of harvesters for crops currently hand-harvested, and the integration of new technologies into current (and future) production systems. Mechanical harvester-based production systems are evolving that reduce field losses and fruit damage, improve recovery, and decrease the foreign materials in the harvested product. However, improved cultural production systems and crop varieties that are adapted for once-over machine harvest are needed. An integrated approach in which crop characteristics along with planting, cultivating, and harvesting techniques are considered will be necessary to develop profitable and highly efficient alternatives to hand-harvest production. The integration of new technologies including differential global positioning systems (DGPS), automatic machine guidance, and computer-based vision systems offers significant performance benefits, and is a substantial component of current vegetable production and harvesting research in the U.S. In time, as the costs of these technologies decline, commercial adoption of these new methods is expected to increase.
The vegetable industry is important to our nation as a provider of nutritious and safe food directly consumed by our citizens. It is also critical to a rich and vigorous national agriculture. During the 20th century, engineering innovations coupled with advances in genetics, crop science, and plant protection have allowed the vegetable industry in the U.S. to plant and harvest significantly more land with higher yields while using less labor. Currently, fresh and processed vegetables generate 16% of all U.S. crop income, but from only 2% of the harvested cropland. Yet, many of the challenges in production that existed a century ago still exist for many crops. Perhaps the most significant challenge confronting the industry is labor, often accounting for 50% of all production costs. A case study of the mechanized production system developed for processed tomatoes (Lycopersicon esculentum) confirms that systematic methodology in which the machines, cultural practices, and cultivars are designed together must be adopted to improve the efficiency of current mechanized systems as well as provide profitable alternatives for crops currently hand-harvested. Only with this approach will horticultural crop production remain competitive and economically viable in the U.S.
In an effort to increase lima bean yields in Delaware, the documentation of lima bean plant development and the comparison of Delaware and California lima bean production was conducted. Delaware lima bean yields have averaged 1905 kg·ha-1 for the last 30 years. California averages 3923-4484 kg·ha-1. Cultivar M-15 is used by both states for production. Plant population density, plant fresh weight, and final yield was greater in California than in Delaware. Although plant populations were the same in 1992, yields remained higher in California than in Delaware. High night temperatures have an adverse affect on lima bean yields. Minimum temperatures from both states were compared. Minimum temperatures from the California planting were greater than the minimum temperatures for the late planting in Delaware.