Club of bologna proceedings

Figure 5
shows the effect of freezing
-
thawing 
cycles on soils, which were primary cultivated 
either beforehand in the winter or in the spring on 
the date, when the secondary cultivation took
place. With the loomy sand soil the time of the 
primary culti
v
ation did not affect the fineness of 
the seedbed after secon
d
ary cultivation.
However, with the clay
-
loam soil the primary
cultivation beforehand in winter resulted in a
much finer seed bed after the same secondary
cultivation. Getting the same fine seedbed for this 
soil with primary cultivation in spring would have 
required 4 times as much energy for several
passes of se
c
ondary cultivation. So on heavy
soils much energy can be saved for secondary 
cultivation, if the primary cultiva
t
ion occurs
several months beforehand.
However, in the usual crop rotation this e
f
fect 
can only be used when preparing for sprin
g
crops. The conclusion from this for farming on 
heavy soil with a high share of spring crops
should be, that a combination of primary and
secondary cultiva tion should be avoided under 
these circumstances. 
The topic of energy need for secondary
cultivation often includes a comparison of p.t.o. 
driven implements on the one hand and only
drawn tools on the other hand. The energy losses 
occuring between the tractor and the implement 
are an important topic. The e nergy transfer to the 
implement tools via the 
p.
t.o. or via the contact 
area between the tractor tires and the soil affects 
these losses. 
Actually the losses via the p.t.o. and the
transmission of the implement almost always will 
be lower, because of the energy wasted by the 
wheel slip associated with
s
olely drawn
machines. Yet comparisons between p.t.o. driven 
and drawn tools in field e
x
periments up to now 
did not demonstrate, that the soil size reduction 
by solely drawn tools is less efficient in the use of 
energy. These comparisons were made taking
into consideration the increase in particle surface 
by the respective energy input [1, 2].
So the question arises, whether p.t.o. driven tools 
do waste energy by other means. And in fact, it 
may be that they do waste energy because the 
soil particles up to
now are a
c
celerated much 
more as with solely drawn tools. The energy
transfered to the soil part
i
cles in accelerating
them is hardly used for breaking them up. So 
improving the energy effi
c
iency of p.t.o. driven 
implements for secondary cultivation prob
a
bly 
means, that either accelerating the soil particles 
should be reduced or the kinetic energy of the 

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accelerated par ticles should be used better to 
crush them.