Chapter 19 Agricultural and Related Technology
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The water in the lateral lines enters the
sprinkler heads, which spray water onto
the land.
Sprinkler systems can have a number
of straight sprinkler lines. Each line can
apply water to a long, narrow band across
the field. The water is allowed to run for a
set time to irrigate the bands on each side
of the sprinkler lines. These lines are then
moved by hand or rolled to the next position.
Here, they apply water to the next bands.
A large number of straight lines can
be used to cover the entire field. When
the lines are turned on, the entire field is
irrigated at once. This eliminates the need
to move individual lines. These lines are
called solid-set sprinklers.
Other sprinkler systems are called
pivot sprinklers. See Figure 19-17.
These systems use one long line that is
attached at one end to a water source.
The line pivots around the point of attach-
ment on large wheels powered by electric
motors. This long line is constantly moving
very slowly in a circle. Sprinkler or mist
heads apply the water as the line pivots.
Drip irrigation is the third type of irri-
gation. The system uses main lines to bring
water near the plants. Individual tubes or
emitters bring water from the main lines to
each plant. This system ensures each plant
is properly watered. Drip irrigation reduces
the amount of water lost to evaporation.
Harvesting Equipment
Once a crop reaches maturity, it must
be harvested. Each type of crop has its own
special harvesting equipment. Combines
are used to harvest grains. See Figure 19-18.
A combine is a combination of two early
farm machines: the header (cuts heads from
the grain) and thresher (removes grain from
chaff). The combine cuts off the tops of the
plants containing the grain. The heads and
straw move into the machine. A cylinder
causes the grain to break away from the
heads. Blasts of air and screens separate
the grain from straw, chaff, and weed seeds.
The grain is moved into storage hoppers on
the machine. The unwanted materials are
conveyed out the back of the machine and
dropped onto the ground.
Figure 19-17. The pivot sprinkler system is irrigating crops. (U.S. Department of Agriculture)