Agriculture Reference
In-Depth Information
This sensing technique is state of the art with many crops. Basing the fertilizer
application on the site-specifi c yield can be recommended provided the respective
nutrients are not lost otherwise in an unregulated manner,
e.g.
by leaching. Hence this
method is feasible for site-specifi c fertilizing of phosphorus and with the exception
of sandy soils also of potash. With nitrogen, the situation is completely different
because of its high disposition to unpredictable leaching, at least in areas with humid
climate. In these areas therefore,
site-specifi c nitrogen fertilization
is a prime
candidate for proximal sensing. This technique can be based on either sensing the
nitrogen supply in the soil or in the crop. Determining the supply in the soil might
rely on the use of ion-selective electrodes or on the refl ectance of mid-infrared
radiation. For sensing the supply of the crop, refl ectance indices that are based on
narrow wavelengths from the red-edge range between the visible and near-infrared
radiation are reliable indicators. This technique of in-season site-specifi c nitrogen
application based on a control in real-time is used commercially and allows small
yield increases or better nitrogen use effi ciencies and hence a reduction of nitrate
leaching into ground-waters. The latter result is very important since less nitrate in
drinking waters is a very urgent environmental objective in humid regions.
Site-specifi c control in the
application of fungicides
can be based on spatial
differences of the crop-biomass or on infected loci. The fi rst approach is state of the
art. The second concept - treating only the infected loci - is still in an experimental
stage, but should be strived for.
The variety of interdependencies between soil-and crop properties as well as
between various farming operations that rely on these calls for
holistic solutions
.
These should, however, avoid information overloads. Concepts that point in this
direction are sensor fusion, map overlay and management zones.
Sensor fusion
aims at recording two or several soil- and crop properties simultaneously in order to
improve the control of farming operations. And urgent approach along this line is
simultaneous sensing and processing information about the nitrogen and water
supply of crops. Because without the uptake of water, any nitrogen fertilization is
useless.
Map overlay
holds for the merging of site-specifi c information from several
maps of the same fi eld. And
management zones
within single fi elds are created
from maps about temporally stable soil properties. All these techniques condense
the site-specifi c information, yet depend on an adequate processing of the data.
Finally, it always should be kept in mind, that precision farming techniques must
comply to spatial, temporal and rate resolutions. The latter term refers to the rate at
which the various farming operations fulfi ll their function. In short, the challenge is
to do the
right thing
at the
right place
and in the
right time
. Meeting these
challenges will provide the means to feed the world population and to protect the
environment.