Agriculture Reference
In-Depth Information
12.1
Introduction
Site-specifi c recording of yields, also known as
geo-referenced yield detection
or
yield measurement, was the fi rst technology in precision farming that was available
as an accessory for combine harvesters in the early 1990th. The objective is to
automatically get information about the heterogeneity of crop yields within fi elds.
In the context of site-specifi c precision farming, geo-referenced detection of
yields has three major objectives:
• It delivers information to determine the
site-specifi c yield potential
of fi elds that
were managed uniformly before the transition to site-specifi c management.
• It gives a
feed-back of the effects on yield
of site-specifi c management.
• It makes it possible to calculate the
export of nutrients
for balancing and
management of plant nutrition.
To fulfi ll these tasks, geo-referenced yield data have to be collected continuously
covering the whole area of a fi eld with an acceptable accuracy.
12.2
Principle of Site-Specifi c Yield Recording
Recording site-specifi c yield data from crops can be provided by some extra
technology on the harvesting equipment. The principle and the components for
most local yield measurement systems include:
•
Product output sensor (
e.g.
grain output)
•
Area sensing (speed and working width)
•
Position detection system (usually differential GNSS)
•
Data processing, -monitoring and -storing unit
•
Data transfer to offi ce computer.
The arrangement and interaction of the subsystems can be seen in Fig.
12.1
,
which shows an example for site-specifi c yield recording in a combine harvester.
The systems to detect the
product output
(t/h) have to be adapted to the
specifi c crop and to the harvesting process and equipment, while sensing the
area
capacity
(ha/h) is realized by measuring the speed of the harvester and multiplying
this by the working width. Dividing the product output by the area capacity
provides the actual local yield data. After a fi rst statistical smoothing (
e.g.
moving
average) this site-specifi c yield in mass per unit area (as well as the product output
and the area capacity) is presented to the machine driver on the information display
and stored typically every second together with the positional data of the harvester
in an electronic device.
Within some time, at least at the end of the harvesting season, the data are trans-
ferred to an offi ce computer for further processing. The media for data transfer have
often changed during the last two decades due to fast technological progress.
