Agriculture Reference
In-Depth Information
a result of less cultivation, the residues of the previous crop remain on or near the
soil surface.
Yet there are important points in favour of reduced- or even
no-tillage
:
• substantial savings in the expenditure of energy and labour
• less decomposition of soil organic matter
• less or no moist soil is moved upwards to the surface, therefore less- or no
artificial clod production occurs
•
crop residues on or near the soil surface can substantially reduce erosion, especially
in areas with continental climate and on slopes.
However, some
consequences
of less or no tillage must also be dealt with:
•
hitherto mechanical weed control via soil cultivation must be compensated for
by more herbicides. This holds especially for regions with maritime climate.
•
since less fungi on crop residues are buried, more fungicides must be used. This
consequence too is more important in maritime regions.
•
the seeding techniques have to cope with crop residues on or near the soil surface.
As a result of more efficient herbicides and fungicides, counteracting to the
consequences for weeds and fungi becomes easier and easier. Yet the conflict
between seeding techniques and crop residues remains and must be taken care of.
With conventional sowing techniques, the residues can seriously reduce the emer-
gence. This can be the result either of less precise seeding depths or of residues that
are placed close to seeds and hence impair the water transfer from the soil to the
seeds. Several strategies to cope with these residue problems are available.
8.4.1
Vertical Discs, Cleaned Rows or Inter-Row Sowing
Openers that employ heavily loaded
vertical discs
often can solve the residue
problem in dry regions with small grains or oil crops, when the soil is rather hard
and the straw is brittle. Under these conditions, the discs just cut through the residues.
In humid areas, this method often fails, since here the soil and the straw are more
flexible. Therefore, the straw is not cut by the disc openers, but instead it is pushed
into the seed furrow. This can seriously impair the emergence.
In maritime climates, the moist straw also tends more to hair-pinning around
seeding devices and hence to clogging.
Sowing into cleaned rows relies on a
local segregation
of the respective areas for
sowing and residues.
Row cleaners
accomplish this by moving the residues ahead
of the openers into the inter-row areas. The implements used for this usually are
vertical, ground-driven, fingered wheels, which are slightly slanted in the direction
of travel as well as perpendicular to it (Fig.
8.11
, left). The rotating fingers act like
rotary rakes and push the residues sidewards. Depending on the depth of operation,
also some strip cultivation (strip tillage) just ahead of the openers can result
(Fig.
8.11
, right). Site-specific depth control of the row-cleaner units via data from
field maps (
e.g.
about soil texture or residues) is possible.
