Club of bologna proceedings

5. Tillage systems 
The results of world
-
wide research show the
ample role of the interactions among tillage
operations and other agronomic practices, so that 
possibilities for new soil management systems are 
made available by increasing both fertilizer rate 
and herbicide use. In orchards plastic mulching or 
grass cover and irrigation can be efficiently
combined with non
-
conventional tillage [38].
Especially in the 70's and 80's, til
l
age problems 
appeared to be more suitably treated within the 
framework of the whole soil management
programme, since the possibilities of radical
changes brought about by the introduction and 
improvement of herbicides. 
Taken from the reviews [8; 11], the most 

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27
important tillage systems can be classified and 
defined as follows: 
Conventional tillage
- Generally refers to
mouldboard ploughing with soil inversion,
followed by a secondary tillage such as discing 
and/or harrowing. Weed control can be
accomplished through cultivation or hebicides 
use. 
Minimum tillage
(reduced tillage) - Is similar to 
conventional tillage, but with fewer trips and
shallower tillage depth. Implements are mainly
discs, chisels (disc planting, wheel
-
track 
planting). 
Mulch tillage
- Th
e
soil is disturbed prior to 
planting. Tillage implements such as chisels, field 
cultivators, disc sweeps, or blades are used.
Weed control is accomplished by he
r
bicides 
and/or cultivation. A mode of mulch tillage for 
small grains is stubble
-
mulch [39] whe re winter 
cereal stubble is left on the su
r
face of the soil 
which is shallow mixed or surface cut without 
inversion (implements for mixing: discs, chisel
-
ploughs, field cultivators, mulch treaders; for 
non-i
nversion: sweeps, rotary rod weeders). 
Ridge-furrow tillage
- The soil is left
undisturbed from harvest to planting except for 
nutrient injection and provides surface drai
n
age 
[40]. Planting is in a seedbed set out in ridges 
with sweeps, disc openers, coulters, or row
cleaners. Residues are left on the
s 
urface 
between the ridges. Weed control is by
herbicides and/or cultivation. 
Chiselling
or 
paraploughing
[11] - Consising 
of subsoiling along the inter
-
row zone to loosen 
the compacted subsoil. 
Strip tillage
or 
zonal tillage
- i.e. cultivation
along the inter-row zone only. 
No-tillage
- Involves complete elimination of
mechanical seedbed preparation (except na
r
row 
bands where the seed is placed) and rel
i
ance on 
herbicides or cover crops or both to control
weeds. In no
-
tillage the soil is left undisturbed 
from harvest to planting, except for possible
nutrient injection. This system includes direct
seeding of small grains. 
The last three tillage classes are known as
"conservation tillages"; the second one may or 
may not qualify in this group depending on the 
amount of residues left on the soil surface after 
seeding [8]. 
No single tillage system is however superior to 
any other and the most suitable system should be 
sought for each pedoclimatic and general
agricultural condition. 
Among the advantages of the so
-
called 
conservation systems, supporters claim effective 
soil erosion control, water conservation and more 
efficient water use, lower energy 
r 
equirements 
(less use of fossil fuels), reduced labour
requirements, more timeliness of til
l
age 
operations, so ensu
r
ing better flexibility with
regard to weather conditions and greater
possibility for double cropping in certain climates 
(which means more intensive use of soils) and 
less risk of environmental poll
u
tion. 
These advantages can be obtained to diffe
r
ent 
extents by one of the above
-
listed soil tillage 
systems. Drawbacks are also recognised, such as 
increased energy costs for herbicides, fertilizer, 
amendments and irr
i
gation; increased herbicide 
use has a worse disadvantage: it contributes
towards dange rous environment pollution, which 
ecologists are striving to oppose; on the other 
hand di
f
ficulties are found in controlling some
weed species. In soils with poor internal drainage 
(most clay soils) conservation tillage can
aggravate wetness limitations in a tempe
r
ate 
climate for both surface temperature and a
n
oxic 
effects beneath. 
The comparison of these systems in different
soils, in diverse climates and in more than one 
year usually shows a very wide variation on the 
yields and the trend over time has not yet be
e
n 
clearly demonstrated in all cases; some long
-
term 
modifications to soil traits are now appearing.
Very often different til
l
age systems give no
significant yield diffe rences in the long
-
term; in a 

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28
single year, however, some relevant differences 
might occ
u
r, which only demonstrate the
existence of strong interactions with seasonal
meteorological events for any given soil and
climate; these effects are usually compensated as 
an average over many years. This is one of the 
reasons for considering the debate s
t
ill open [12; 
14]. When annual yield differences arise this
mostly depends on the effects on early crop
development; usually the reasons for these
differences are not clear or at most not clearly 
demonstrated; e.g. it can be that excess water 
drainage and consequently be tter root deepening 
are the cause [28]. 
According to most authors [7; 12; 14; 8] the 
conditions for which, at least on average, each of 
the tillage systems seems advisable can be
identified in the following way:
°
conventional mouldboard plou ghing fo
l
lowed 
by secondary tillage operations still seems the 
best solution for soils where internal drainage 
is a problem, such as clay soils with poor 
structure, and for most crops, but especially 
for sugarbeet, carrots and similar crops (