Club of bologna proceedings

6. Conclusions 
The soil bulk density and 
-
particle size
s
needed 
depend on the long term climate as well as the 
short term weather. Adapting the cultivation
technologies to the climate hardly is a pro
b
lem, 
but to the not foreseeable weather is impossible. 
Advances in reliable weather
-
forecasting are
urgently needed. 
The progress with efficient and environme
n
tally 
safe herbicides combined with crops made
resistant to them by genetic engi
n
eering will
probably more and more reduce mechanical
weed control by plowing. 
The prevention of soil surface crusting r
e
quires 
particle size segregration by secondary cultivation 
in some cases. This process needs slowly moving 
tines and thus up to now di
s
pensing with p.t.o. 
driven tools. 
The energy for soil
-
breakup by secondary
cultivation can be re
d
uced substantially by
weathering effects. However, this advan tage can 
be used only when a long time span b
e
tween 
harvesting and sowing of the subs
e
quent crop 

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51
exists. 
Secondary cultivation by solely drawn tools often 
is associated with energy waste because of
tractor wheel slip. Th is waste can be avoided by 
p.t.o. driven tines, yet their e
n
ergy efficiency up 
to now is much impaired by the high acceleration 
of soil particles. 
Straw in the seedbed increasingly is a pro
b
lem 
for cultivation methods without plowing. It can
substantially reduce the field eme rgence, because 
it deteriorates the precision of the sowing depth 
obtained with traditional openers, and because it 
alters the air to water supply of the seeds.
Negative chemical effects of watery extracts from 
straw on the germination on filter paper often
show up in laboratory experi
m
ents. However, 
these detrimental effects were not noticed in
artificial or natural soils. For practical purposes 
they probably can be neglected. 
Remedies for the straw problem can be sowing 
methods, which
can cope better with crop
residues, or placing the straw on top of the
seedbed instead of incorporating it, or breaking it 
up much more by the combine. All three methods 
can improve the emergence.