Agriculture Reference
In-Depth Information
needs for specifi c and uniform plant products necessitate annual monoplant fi elds
and thus soil cultivation, either as
primary cultivation
(ca.10-30 cm deep),
sec-
ondary cultivation
or
seedbed preparation
(less than 10 cm deep) and in some
cases also postharvest
stubble- or fallow cultivation
.
Precision in soil cultivation should be focussed at
•
creating the bulk density needed for effi cient plant growth
•
providing the soil aggregate sizes that guarantee a high emergence of seeds
•
weed control
•
crop residue management
•
water management.
All these efforts can be queried. In fact, some farmers plant crops without any
previous cultivation. A soil, which is high in organic matter content may - without
any cultivation - provide the bulk density as well as the soil aggregates needed.
Weed control can be taken care of completely by herbicides. And if crop residues
just are left on the soil surface, they can effi ciently reduce soil erosion. So why
worry to get them buried?
Yet again, there are also serious limits to these options. Not all soils have a suf-
fi ciently high organic matter content. Very often soils get compacted by heavy har-
vesting machinery as well as by post-harvest rain, hence necessitating cultivation.
Weed control solely by herbicides can be costly. And last but not least, crop residues
in the seedbed can seriously impair the emergence of seeds. This applies especially
to narrowly spaced crops such as the widely used small grains in high yielding areas
and when short time spans between harvesting and sowing prevail.
In short, despite the advances in zero- and minimum tillage practices, the major-
ity of the farmers still has to cultivate. For these farmers, cultivation might take
between 30 and 50 % of the energy needed for all fi eld operations. Yet more preci-
sion in cultivation is urgently needed and might help to reduce the present contro-
versies about soil cultivation techniques.
7.2
Primary Cultivation
Two effects deserve attention:
•
the soil inversion and
•
the depth of cultivation.
It is generally known that only the
mouldboard plough
can provide for an effective
soil inversion and thus for a rather complete burial of weeds as well as of crop residues.
All other implements just mix the soil and therefore leave some weeds and residues on
the surface. The result is that the plough is the most effective tool for mechanical weed
control and does away with all problems arising from residues in sowing operations.
Yet on the other hand, the plough is a very energy- plus labour consuming tool.
And the bare surface left by the plough induces soil erosion. This holds true espe-
cially for sloped fi elds with silty soils in continental climate.
