Agriculture Reference
In-Depth Information
7.4.1.2 Plant Shape and Size
The ideal configuration for efficient robotic harvesting would be a vertical or slightly
inclined hedge wall, 10 to 12 ft tall, which is relatively uniform, smooth, and con-
tinuous from start to row end. The fruit would be located on the canopy surface with
minimal occlusion. In reality, this would not be the case, but it provides some insight
into what the robot would need in order to maintain fast harvest cycle times and
maximum fruit removal. Deviations from the ideal will cost removal efficiency and
cycle time performance.
Orchards should have uniform plant sizes and predictable shapes for efficient
robotic harvesting (Cargill, 1983). Standardization of tree sizes significantly improves
harvesting throughput and thus economic benefit. These standard sizes should con-
sider tree height, tree thickness, tree shape, and tree spacing within and between rows,
so the robotic equipment can maintain continuous harvesting, with minimal idle har-
vest time when traveling between trees. A number of these features are designed into
the grove at planting, whereas others must be maintained mechanically through cul-
tural practices. A common modern approach for maintaining both tree size and shape
is mechanical pruning. The trees can be pruned to the desired shape before fruit sets
and allowed to grow during the remainder of the year. In some limited cases, severe
pruning is being tested. Under this practice, alternating sides of the tree are pruned
each year and allowed to set fallow, while the other side of the tree produces the
current year's crop. When the canopy returns the following year, the woody mass is
covered by the new growth and a relatively uniform vertical wall is achieved. Impact
of annual fruit yield has not been reported on this technique to date.
Experiments conducted on apples demonstrated that tree shape contributed
toward the suitability of mechanical harvesting (Zocca, 1983). Modifications to cul-
tural practices for growing and harvesting fruit are important for successful mechan-
ical harvesting. A mechanized pruner was developed that not only reduced the labor
required for pruning, but also properly shaped the hedgerow for maximum harvest-
ing efficiency of erect cane fruits (Morris, 1983).
Ben-Tal (1983) points out several problems that can arise when an orchard is pre-
pared through pruning for a specific kind of equipment, such as reduced yield, fruit
quality, and the number of years of production. Additional issues such as canopy
light exposure and maximum height of a tree for proper spraying and pruning should
be considered. The question of plant geometry and its relationship to productivity
needs to be thoroughly examined (Rohrbach, 1983).
7.4.1.3 Tree Genetics for Optimal Harvesting
Plant breeders developing new varieties of fruit must consider if the variety will
be accepted at market and if it will be durable under machine handling. Attractive
appearance and long shelf-life are imperative in the fresh market. Varieties must be
resistant to bruising, cracking, and rupturing during machine handling. The fruit
must be relatively easy to remove from the plant, and the peduncle must remain
attached (Davis, 1969; Lapushner et al., 1983).
In addition to fruit-related issues, there are a number of tree factors that can be
improved genetically that can enhance robotic harvestability. Two major obstacles
