Agriculture Reference
In-Depth Information
The steady advances in
chemical weed control
induce farmers more and more
to rely on herbicides instead of the plough. From an environmental point of view,
the herbicides as well as the plough can be questioned. Yet the future looks brighter
for weed control by herbicides than for weed control by the plough. The advances
which have been made for effi cient and environmentally safe herbicides as well as
for crops made resistant to herbicides by genetic progress are remarkable. It will
hardly be possible to offset these advances by better ploughs.
There still may be negative effects of residues from the previous crop on the
emergence of seeds. They mainly result from a less accurate seed placement in the
soil by the openers of the sowing machines because of the residues. Yet this obstacle
to cultivation without soil inversion by a plough too is losing its impact. Several
means of eliminating negative effects of
crop residues
on or in the seedbed on the
emergence have been developed. Examples are openers, which hardly are affected
in their seed placement by residues or raking devices which operate ahead of the
coulters and move the residues in the area between the rows (row cleaners). At least
with widely spaced crops such as maize, soybeans and beets, these row cleaners can
be used successfully. Modern harvesting machines too substantially can alleviate
the problem by leaving fi nely chopped- and uniformly distributed residues on the
fi eld. In short, crop residue management also less and less requires ploughing.
The subsequent text therefore deals primarily with problems and solutions for
precision cultivation with tined implements.
7.2.1
Factors for the Depth of Primary Cultivation
The bulk density needed for effi cient plant growth is mainly regulated by the
depth of the primary cultivation. The deeper the primary cultivation tools operate,
the more the soil is elevated above the original surface, thus the more the bulk
density is lowered. Methods for recording the bulk density in the laboratory are
state of the art. However, sensing techniques capable of recording the bulk density
in a continuous manner online on-the-go are not available. But a feasible approach
is to adjust and to control the depth of the primary cultivation according to sur-
rogates such as
•
water supply
•
texture
•
organic matter
•
slope
•
resistance to penetration.
7.2.1.1
Water Supply
Precipitation increases bulk density of soils. This holds especially for bare soils. But
when it comes to adapting cultural practices to precipitation, it is helpful to differenti-
ate between climate and weather.
Climate
acts on large, contiguous areas and is
