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1998 CoB Vol 09

6. Conclusions 
Seed bed preparation is a costly investment in crop 
production; it is relatively more important for field 
crops, especially in its most extensive form. Soil 
tillage has always required farmers' attention; 
economy [41] much more than energy balance or 
"emergy" being pre-eminent. 
After thousands of years of slow evolution, the 
mouldboard plough attained a dominant role in seed 
bed preparation. This solid myth crumbled, however, 
under the intensive research of more than half a 
century. This doesn't at all mean that the traditional 
ploughing system will disappear; it only means that 
conventional tillage should be selected or retained 
where and when there is a reasonable argument to 
prefer it or not to abandon it. 
The many different tillage implements avaiable today 
for seed bed preparation act differently on the soil; 
these actions combined with other agronomic practi-
ces (such as crop residue management, seeding 
technique, herbicide use, fertilizer and irrigation rate) 
and meteorological conditions develop very 
complicated interactions, which are not yet throughly 
understood and the effects of which can be very 
different and open to ample technical possibilities. In 
the field farmer's experience is still very valuable and 
eventually expert systems should be preferred to 
mathematical models. 
On the basis of the many, in principle well-
established, actions of different tillage operations it is 
possible to develop tillage and management systems 
which go from traditional more or less deep 
ploughing followed by secondary tillage 
operations, to no-tillage; many intermediate systems 
have been proposed both as a rule or as a contingent 
solution. Some of them are very efficient in erosion 
control and in building a stable soil structure, with 
agronomic consequences (runoff control, o.m. 
balance, effects on soil compaction, protection from 
tropical high soil temperature); in some cases 
drainage is hindered and germination is delayed by 
low soil surface temperature. The needs alter in 
different conditions (slopes, crusting soils, dry or wet 
climates, etc.) and for different crops. In orchards 
competition for water is a limiting factor for 
permanent grass cover, even when irrigation is 
available. 
The trend on a world basis seems to indicate an 
increase, to a certain extent, of the area sown after 
minimum tillage or no-till. Future developments are 
still uncertain; at least for some extensive crops they 
will depend mainly on the evolution of herbicide 
techniques and the possibility of reducing 
environmental chemical pollution to an acceptable 
level. The combination of transgenic varieties 
resistant to given herbicides, these being efficient 
against perennials and at the same time not selecting 
resistant weeds, is expected to open up new 
possibilities for some crops (e.g. maize and 
soybean); the problem is in any case not simple, 
being connected to the whole question of transgenic 
varieties. The whole must be seen within the 
framework of a hoped precision-agriculture, which 
implies social progress and innovation in the 
farming world. 
The criteria that the operator should keep in mind in 
decision-making are: labour cost, equipment cost, 
adaptation to soils (espcially drainage ability) and to 
climate (cold temperate, warm, dry winter, dry 
summer, winter freeze, etc.), adaptation to the crop 
species grown (some require deeper tillage) and 
flexibility in the case of changing crops in a rotation, 
herbicide and any fertilizer and irrigation costs, 
operation simplicity and rapidity, mean yield (after 
reaching steady 


31
state conditions) and yield variability from year to 
year. In heavy clay soils traditional ploughing
usually proves better and stabilizes yields. All
these aspects should be weighted according to 
single situations an d crops and then added up to 
reach a comprehensive 
d
ecision. No unique
judgement on tillage system is therefore possible. 
For public administrators the criteria of i
n
terest 
are usually general economic welfare as well as 
control of hydrological (including runoff) and
erosion consequences, pollution of water bodies, 
eutrofication, environmental protection (including 
herbicide diffusion in the environment). Some of 
the tillage alte rnatives to conventional ploughing 
are more efficient for this purpose, at leas
t
in 
some conditions. Have these authorities the
means to intervene in this direction? The cost to 
the community could be high, but what is more 
serious is the question: is our present know
l
edge 
sufficiently sound for valid public i nterventions? It 
seems that a lot of improvments have been
made in the 20th century, but there is much more 
we need to know quantitatively, rather than by 
simple descri ption, faced with the perspectives 
opening up in the third millennium.

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