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Section 4 Technological Contexts
harrow is a frame with teeth. These teeth
can be spikes or spring shaped. The
harrow is dragged over the ground to give
the soil tilth. Tilth means fine and crumbly
soil.
Today, farmers are reducing the
amount of tillage they do. This is espe-
cially true on soil that can erode easily.
This technique is called minimum tillage.
Minimum tillage uses small amounts of
work to prepare the soil. Often, a set of
chisels on a frame is used to open the
soil. In some cases, no-tillage systems are
used. In these cases, crops are planted
without working the soil from the previous
crop. Special planters slice open the soil
and plant the seeds.
Planting Equipment
Once the soil is prepared, fertilizer must
be applied. Fertilizer is a liquid, a powder,
or pellets containing important chemicals.
This substance primarily delivers nitrogen,
phosphorus, and potassium to the soil.
Other nutrients are also in many fertilizers.
Fertilizer can be applied before, during,
or after planting seeds. This substance
can be applied with special equipment
or along with a seed planter. Often, dry
fertilizer is scattered (broadcast) before
planting. Liquid and gaseous (anhydrous-
ammonia) fertilizer is applied by injecting
it into the soil. A machine with a series of
knives is pulled over the ground. The liquid
or gaseous fertilizer is injected into the
trench the knives create.
The seeds must be planted to start the
crop cycle. Over most of history, this was
done by hand. In the early 1700s, however,
a new machine was developed. This
machine is called the seed drill, or grain
drill. See Figure 19-11. As it is pulled
along, it opens a shallow trench. A seed
is then dropped. The trench is closed,
covering the seed.
Other planting machines have been
developed for potatoes and corn. See
Figure 19-12. Specialized machines are
used to plant vegetable plants, such as
tomatoes and cabbage.
Pest-Control
Equipment
In nature, not all plants that sprout live
to maturity. Diseases and insects kill some
of the plants. Neighboring plants crowd out
others. Farm crops face the same dangers.
A number of machines have been devel-
oped to help control these pests.
Figure 19-11. A grain drill in use. (Deere and
Company)
Figure 19-12. This farmer is planting corn with
a six-row corn planter. Fertilizer is applied from the
front hoppers. Corn seed is in the back hoppers.
(Deere and Company)