Agriculture Reference
In-Depth Information
two-pass system - georeferencing and mapping essential
sensor
spreader
one-pass system - georeferencing and mapping not essential
sensor
spreader
Fig. 3.7
Tractor-based control for site-specifi c spreading of fertilizer with or without mapping
Wide area maps and farm maps are predominantly used for
tactical inspections
of f
the situation. In a similar way like a mirror might allow to see around corners, these
maps make it possible to get an overview of the coverage of large areas from a central
bureau, and this within a few minutes. During the growing period, these tactical inspec-
tions can be useful in time intervals ranging from several days to several weeks,
e.g.
in
order to see how the crops develop. The maps can be supplied easily and at reasonable
cost via internet from polar satellites that orbit the respective areas every day. Limitations
can exist in some agricultural regions for maps that rely on visible- and infrared radia-
tion as a result of the effect of clouds (Sect.
3.3
). Yet for some soil- and crop properties
(Table
3.2
), the cloud problem can be overcome by using radar waves instead of visible-
and infrared radiation. The steady advances in sensing by radar waves facilitate this.
With fi eld maps, the situation is different. They might sometimes be used for
tactical inspections as well, but this is not the most important application. The pref-
erential use in precision farming is for the control of
site-specifi c fi eld operations.
Some properties that are recorded in fi eld maps are temporally constant, others are
not constant over time at all. Maps about texture, organic matter content and contour
lines of soil can be regarded as being up to date for a long time and hence be used
for many years. To a somewhat lesser extent, this also applies to maps about the pH
of soils. But there are many soil- and crop properties that do not allow to use the
same map for several consecutive fi eld operations or years. The plant available
nitrogen- and water content in soils can change within some days. The same applies
to growth stages or infestations of crops with fungi or insects.
The ideal control technique for site-specifi c operations when the soil- or crop
properties change fast in time is online
real-time sensing
combined with on-the-go
adjustment of the farm machine (Fig.
3.7
). This technique allows for the best
