Agriculture Reference
In-Depth Information
Sometimes dug potatoes may be left in the field so that the soil can dry, making it easier
to remove.
Simple plowing with animal or tractor power followed by manually collecting the
tubers is also done in many localities. This method requires careful and relatively deep
plowing to expose the tubers without causing damage to too much of the harvest. In
Figure 5.8 the line at the bottom of the ridge, of the bed, is the depth to which soil is
plowed or dug.
Many types of mechanical tuber harvesters are available. Some dig plants and
tubers with a scooplike harvester, that lifts the plants and tubers out of and separates
them from the soil on a moving screen conveyer and leaves them piled in a row,
called a windrow, in the field. Complete mechanical harvesting is done with a
similar scoop that cuts below the plants (Fig. 5.11) and lifts them out of the ground
and onto a moving conveyer screen where soil and rocks fall through the screen
and the tubers are collected in a wagon at the side of the conveyer (Fig. 5.11).
In most cases tubers harvested by mechanical means are ready for sale immediately
after harvesting. However, complete removal of stones and rocks from soil is not
always accomplished, and so some additional sorting may also be needed before
further processing of the tubers.
Once harvested, potatoes are dried and stored in a cool dark storage facility. In the
past this has been a dark, cool cellar of a house and was called a root cellar. Storage at
temperatures below about 78C is usually effective in inhibiting the growth of disease-
causing bacteria and fungi. However, freezing can cause damage to tubers, and thus the
temperature cannot be allowed to get too low.
5.5.7 Consumption
In tropical climates dried tubers can be stored for short periods of time, although they
are more commonly eaten fresh. In most cases plants are left in the field and tubers har-
vested as needed for food or when they are to be sold in the local market. Additional
information about consumption is given below.
5.5.8 World Production
Potatoes and sweet potatoes are native to South America while the yam is reported to be
native to both South America and Africa. The origins of other root crops are
largely unknown.
Potatoes (Solanum tuberosum) shown growing in Figure 5.9, sweet potatoes
(Ipomoea batatas), in Figure 5.10, and boniato and yams (Dioscorea cyenensis) are
all tubers of vines. Although sweet potatoes and yams are often confused and the
names used interchangeably, they are, as seen by their scientific names, entirely differ-
ent plants. Of these tubers boniato is an exception in that it is classified as Ipomoea
batatas and so is another variety of sweet potato, although as seen in Figure 5.4 the
sweet potato and boniato look quite different.
As shown in Figure 5.12, potatoes are grown on every continent and in almost
every country in the world. On the other hand the production of other root crops, for
