| Introduction
When I was invited to present this paper on the "frontiers
of conservation tillage" from a global perspective, I at
first refused because it seemed a very difficult task. The United
States is among the few countries in the world that has yearly
statistics on the different forms of conservation tillage. Information
on conservation tillage in other parts of the world is scarce
or nonexistent. Another problem associated with conservation
tillage is its definition. There is confusion in the term conservation
as well in the term tillage. When reducing conservation tillage
to no-tillage, information is easier to get and for this reason
I will concentrate on this praxis, although one must be aware
that information remains imprecise. As most of my working experience
with no-tillage has been gained in South America, my remarks
will concentrate on this part of the world. It is interesting
to note that in the U.S., no-tillage accounted for just 44%
of all cropland hectares planted in conservation tillage in
1998, while in South America no-tillage probably accounts for
more than 95% of conservation tillage area.
No-tillage is defined in this paper as the planting of crops
in previously unprepared soil by opening a narrow slot, trench
or band only of sufficient width and depth to obtain proper
seed coverage. No other soil preparation is performed (Phillips
and Young, 1973). We also refer here to permanent no-tillage
rather than not tilling the soil occasionally. It is understood
that the soil remains covered by crop residues from previous
cash crops or green manure cover crops (GMCCs) and that most
of the crop residues remain undisturbed at the soil surface
after seeding. As long as this requirement is met, shanks can
be used to break compacted soil layers below the seed zone.
Therefore the term direct seeding (also used in translation
in South America), is more appropriate than no-tillage unless
we use this term in a broader sense. We have to understand that
soil carbon and crop residues are key factors for no-tillage
to function. We have concentrated too much and too long on not
tilling the soil instead of concentrating on crop residues as
a main tool for management (Wayne Reeves, personal communication
1997).
Control of soil erosion is still one of the main driving forces
for no-tillage adoption. No technique yet devised by mankind
has been anywhere near as effective as no-tillage at halting
soil erosion and making food production truly sustainable (Baker
et al., 1996). The long term gains from widespread conversion
to no-tillage could be greater than from any other innovation
in third world agricultural production (Warren, 1983).
General situation of no-tillage in the world
The countries in the world with the largest area under
no-tillage are the U.S. with 19.3 million hectares, Brazil with
11.2 million ha, Argentina with 7.3 million ha, Canada with
about 4.1 million ha, Australia with 1 million ha and Paraguay
with 790,000 ha (Table 1). In Paraguay, no-tillage was practiced
on only 20,000 ha in 1992 but grew to 790,000 ha in 1999. It
is not easy to get information about the spread of no-tillage
in Asia, Africa and the East European countries. Admitting that
there may be many gaps in information it is estimated that no-tillage
is practiced on about 45 million hectares worldwide. Approximately
96% of the technology is practiced in the Americas (North and
South) and probably less than 4% in the rest of the world. About
52% of no-tillage is practiced in the U.S. and Canada, 44% in
Latin America, 2% in Australia and 2% in the rest of the world,
including Europe, Africa and Asia. There is a very big potential
to bring this soil conserving technology to these parts of the
world, although limiting climatic and socio-economic factors
have to be taken into account. The East European countries seem
to have the biggest potential for a fast growth of this technology.
In order to overcome the information gaps relating mainly to
the East European countries as well as Africa and Asia, the
author would welcome any information about the area of no-tillage
and conservation tillage being applied in those parts of the
world.
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Table
1: Total area under
no-tillage in different countries (hectares)
| Country |
1998/1999 |
| USA |
19,750,0001 |
| Brazil |
12,000,0002 |
| Australia |
8,640,0003 |
| Argentina |
8,000,0004 |
| Canada |
4,080,0005 |
| Paraguay |
800,0006 |
| Mexico |
650,0007 |
| Bolivia |
200,0008 |
| Chile |
96,0009 |
| Columbia |
70,00010 |
| Uruguay |
50,00011 |
| Others |
1,000,000 |
| TOTAL |
55,386,000 |
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Although the biggest area under no-tillage is found in the
U.S., in this country the technology is applied only on 16.3%
of the total cultivated area, compared to 21% in Brazil, 32%
in Argentina and 52% in Paraguay. In relation to the total
cultivated area, Paraguay has the highest adoption rate of
no-tillage in the world (Figure 1).
A study of the potential use of no-tillage in Africa has been
made by GTZ in 1998. The study concludes that no-tillage ensures
optimum soil protection and is therefore the system of choice
for those regions where sufficient biomass can be produced
to provide year-round ground cover. The ecological constraining
factors for spreading no-tillage in this continent are: low
precipitation with low biomass production, short growing seasons,
sandy soils with tendency to compaction and soils at risk
of water-logging. The socio-economic constraining factors
are: strong demand for crop residues as forage for livestock,
uncertain land use rights, poorly developed infrastructure
(market, credit, extension service), distinct market preference
for one crop (e.g. maize), and high demand on farm management.
The study also concludes that in regions and under conditions
where no-tillage is not possible, the second best choice is
minimum tillage (GTZ, 1998).
While no-tillage was researched in the U.S. in the 1940s and
'50s, and in Europe in the '60s and '70s, it was not until
1971 that research on this technology started in Brazil and
Latin America (Derpsch, 1998). At first no-tillage was conceived
as an efficient technology for soil conservation, since the
spread of arable farming had brought about widespread erosion
in the southern states of Brazil. With time, the technology
has evolved to a truly sustainable production system with
positive economic, environmental and social consequences.
In the MERCOSUR Countries (Brazil, Argentina, Paraguay and
Uruguay) the technology has experienced a twenty-fold expansion
between 1987 and 1997, versus a 4.6-fold increase of the area
in the U.S. in the same period (Figure 2). From 1997 to 1998
the MERCOSUR Countries experienced an expansion of 28% of
the area under no-tillage as against 3.7% in the U.S. The
following are some of the factors associated with this rapid
change in Latin America:
- No-tillage offered efficient erosion control under climatic
conditions with high potential for soil erosion and degradation.
- Appropriate knowledge was available through research and
development as well as farmers' experiences.
- There has been widespread use of cover crops for weed
suppression (reducing the use of herbicides), organic matter
build-up, biological pest control, etc.
- A consistent, positive message about no-tillage has generally
been voiced by all sectors involved, private and public.
- No-tillage has been the only conservation tillage technology
recommended to farmers.
- There has been aggressive farmer-to-farmer extension through
farmers' associations.
- Publications with adequate, practical information were
made available to farmers and extensionists.
- Economic evaluations using a system approach showed substantial,
immediate economic returns for no-tillage, including no-till
with cover crops and crop rotations.
- There have been no major forces against the system.
- Latin American farmers have had to be very competitive
in the global market since in general there are no subsidies.
Constraints
to no-tillage adoption in South America, and how they have
been overcome
Adequate machines
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Only in 1975 were the first machines for no-tillage built
in Brazil, so many farmers started no-tillage by transforming
their old equipment. The first machines built in Brazil (based
on the Howard Rotacaster rotary hoe) were slow and farmers
were very enthusiastic when the faster, triple-disc machines
appeared on the local market in 1976. Importing no-tillage
machines has been almost impossible in Brazil because of high
import taxes. Production in other Latin American countries,
such as Argentina and Mexico, started much later. Today about
15 companies in Brazil and about 30 in Argentina are building
no-tillage equipment.
For small- and medium-sized mechanized farms, we recommend
that farmers buy a no-tillage machine suitable for wide-row
crops (soybeans, maize, sorghum, sunflower) and narrow-row
crops (wheat, oats, rye and green manure cover crops). Failure
to buy a multi-purpose machine puts limited-resource farmers
in a situation in which they cannot plant narrow-row crops
and therefore they are not able to seed small grains or green
manure cover crops and use adequate crop rotations. Leaving
the land fallow during winter results in high weed infestation
and high costs to eliminate these weeds.
Adequate herbicides
The first years of no-tillage adoption in South America
in the 1970s were difficult because the only herbicides available
were Paraquat and 2,4-D. Hand hoeing saved many crops from
failure at this stage. In the early 1980s the number of herbicides
available had grown to such an extent that it was difficult
to know the properties of each of the products. The only people
that had information about the different products' characteristics
were the companies producing them. This made it difficult
for farmers to find the products they needed. Two publications
written in the early 1980s (and now in their 4th editions)
helped to overcome this bottleneck and enabled more farmers
to adopt the system (Rodrigues and Almeida, 1998; Lorenzi,
1994).
The availability of a greater variety of more efficient herbicides,
together with a greater diversity of more efficient no-tillage
seeding equipment in Brazil and Argentina, has led to an unprecedented
growth of no-tillage in South America.
Mental change
A mental change of farmers, technicians, extensionists
and researchers away from soil-degrading tillage operations
and towards sustainable production systems like no-tillage
was essential. As long as the head stays conventional it will
be difficult to implement successful no-tillage in practical
farming. We found that this is true not just for farmers but
for technicians, extensionists and scientists as well. No-tillage
is so different from conventional tillage, turning everything
upside down, that anybody who wants to succeed with the technology
has to forget most everything they know about conventional
tillage systems and be prepared to learn.
Knowledge
Site-specific knowledge of the no-tillage system
has most likely been the main limitation to the spread of
the system in Latin America. The biggest change a farmer has
to face when moving from conventional to no-tillage is probably
weed control. To be able to manage this new situation a farmer
has to have a good knowledge especially of herbicides, weeds
and application technology.
Herbicides
A comprehensive publication is needed that describes
all the products available with all their chemical and toxicological
characteristics, amount to be used per hectare as well as
listing of the weeds that can be efficiently controlled by
each specific product. This is very necessary information
without which not only farmers, but also technicians, extensionists
and scientists will have a hard time making no-tillage work.
An example is the publication by Rodrigues and Almeyda (1998)
in Brazil.
Weeds
Also needed is a publication describing and depicting the
most common weeds. A very useful publication that describes
common weeds, shows pictures of the adult plant as well as
of seeds and seedlings and also lists which herbicides can
efficiently control each weed was published by Lorenzi (1994)
and has been an important tool for farmers and researchers.
This publication has also been reissued four times to date.
Herbicide application technology
The complex calculations of volume of water to be applied
per hectare, pressure, nozzle output, tractor velocity, tank
capacity and amount of product to apply the recommended rate
per unit of area, pose a difficult task. We learned that unless
easy-to-follow information is given to the farmer, imperfect
calibration will result in poor weed control even if using
the best product. Adding to that, in South America it took
many years of adaptive research and collection of farmers
experience before we learned that many products work better
with less than 100 liters of water per hectare than with more,
that in some cases we can reduce significantly the amount
of herbicide used by lowering the pH of the water to 3.5,
that costs and time of application can be greatly reduced
by using big spraying tanks (2000 liter capacity instead of
common 600-liter tanks) and low volume. With time we also
learned that light influences the efficiency of some products
significantly and that in the tropics farmers have to get
up very early to meet spraying requirements of less than 30°
C air temperature and more than 60% moisture in the air. In
some regions and in the hot season we have difficulty meeting
these conditions at any time of the day. Although isolated
information has been published and released every now and
then, it was only in 1996 that a more advanced publication
on application technology was made available to farmers in
Brazil (Fundação ABC, 1996).
Soils
Many tropical soils are acid or have toxic aluminum. We have
been recommending that farmers apply lime the year before
entering no-tillage because it is the last opportunity to
incorporate it. Newer research has shown us that farmers can
also apply lime without incorporating, since in the generally
very permeable tropical soils, with high infiltration rates,
lime moves into deeper soil layers. In this case it is recommended
that farmers apply small rates of lime each year, instead
of applying big amounts only once.
Concepts about liming and fertilization have changed a lot
in Latin America after shifting to the no-tillage system.
Experience shows us that we have to forget everything we have
learned in the university about fertilization and liming and
get acquainted with new concepts in fertility management in
this system. Pioneer farmer Nonô Pereira of Ponta Grossa,
Paraná, Brazil, together with the soil scientist Joao
Carlos Moraes de Sá have developed a system of no-tillage
into native pasture on soils that have a high aluminum saturation,
low pH and in general low fertility levels (farmers spray
off the native pasture 3 to 4 months before seeding to ensure
a good kill of woody grasses). Despite these challenging conditions,
farmers applying relatively low amounts of lime on the soil
surface and using medium fertilizer levels can harvest around
3,000 kg/ha soybeans in the first year. This is probably due
to the high organic matter content of these soils, which have
never been touched by tillage tools before. Similar experiences
are now being made on poor, acid soils and native pasture
in Paraguay.
Soil crusting
In general, crusting of soils is not a problem in no-tillage.
Because the mulch cover avoids the direct impact of raindrops
on the soil surface, crusts do not develop. We have found
that soils which tend to crust very badly in conventional
tillage do not present crusting problems in no-tillage, as
long as the soil is well covered with plant residues.
It is widely known that badly drained soils are not suited
for no-tillage. Luckily most South American tropical soils
are well drained and generally well suited for this technology.
Soil surface roughness
It is obvious that a no-till seeding machine is not going
to work properly if the soil surface is not level. In conventional
tillage farmers often control weeds by mechanical cultivation.
This tends to leave an undulating soil surface that has to
be leveled before entering the no-tillage system. If erosion
rills or small gullies are present, or if for other reasons
a rough surface is left after harvest, we recommend that farmers
level the soil surface before starting no-tillage to avoid
seeding problems and bad stands.
Soil compaction
Tillage-induced soil compaction inherent to conventional
tillage, like plow pans or heavy disc harrow pans, should
be eliminated before entering no-tillage. A chisel plow (in
rare cases a subsoiler) will generally be sufficient in Brazil,
Paraguay and Argentina to solve these problems.
Soil compaction in permanent no-tillage is an issue that is
discussed over and over again in Latin America. We have found
that researchers have a different perception of this problem
than farmers. Since researchers have sophisticated tools to
measure compaction and can easily demonstrate that soils are
more compact under no-tillage than under conventional tillage,
many researchers regard compaction as a very serious problem
in no-tillage. In general scientists and researchers in Latin
America tend to overstate the problem of soil compaction.
Farmers in Latin America, however, measure compaction not
in terms of soil density in g/cm3 or in penetration resistance
but in terms of crop response and yields. If yields are as
good or better in no-tillage than in conventional tillage,
the farmer does not care about compaction. Farmers also measure
compaction in terms of penetration of seeding equipment into
the soil. If soils are too hard to give good penetration to
the cutting elements of a planter then the farmer is going
to have a bad stand.
For the purpose of evaluating farmers' perception of the problem
of soil compaction, three no-till pioneer farmers from Brazil
where interviewed in 1997. The interviewed farmers were Nonô
Pereira (22 years of permanent no-tillage), Frank Dikstra
(22 years of continuous no-tillage) and Herbert Bartz (26
years of continuous no-tillage), totaling 70 years of experience.
Their soils vary from about 80% sand to about 80% clay. The
farmers were unanimous in stating that they do not perceive
compaction as a problem in permanent no-tillage (Revista Plantio
Direto, 1999). They also stated that there is no need to till
the soil every so often once no-tillage has been established.
Finally they said that the best way to avoid compaction in
the no-tillage system is to produce maximum amounts of soil
cover using green manure cover crops and crop rotations, so
that roots and biological activity as well as earthworms and
insects, etc., loosen the soil. Good soil cover is also essential
to maintain higher moisture content on the soil surface and
this will result in better penetration of cutting elements
of the seeding equipment.
Mulch cover
Permanent soil cover with a thick layer of mulch
has been a key factor for success in no-tillage in Latin America.
Farmers who have not understood the importance of a mulch
cover have not yet understood the system. We aim to have at
least 6 and if possible more than 10 tons of dry matter from
green manure cover crops (GMCCs) and cash crops per hectare
per year. This way we have good weed suppression, positive
effects of mulch on soil moisture and soil temperature, and
improve chemical, physical and biological soil fertility.
We not only look at the amount of mulch but on distribution
as well. Harvesting machines should have spread the mulch
evenly over the whole cutting width. Machine manufacturers
have seldom understood this requirement of no-tillage, the
result being an uneven distribution of plant residues, with
excessive mulch in the center and too little or none at the
end. This results in poor performance of herbicides and seeding
equipment.
Besides the limiting factors mentioned, a farmer also has
to learn about the influence of no-tillage on chemical, physical
and biological soil properties, its impact on surface water
and the environment, on yields and most important on the economics
of the system. Several comprehensive publications with research
results have been published in the region since 1981 (see
references below). The proceedings of many conferences held
in Argentina, Brazil, Chile and Paraguay also contain detailed
information. In this respect AAPRESID in Argentina and FEBRAPDP
in Brazil (the federations of no-till farmers in each country)
have contributed strongly to the diffusion of site-specific
knowledge.
Primary needs
associated with no-till's further use and adaptation
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Crop rotations and green manure cover crops
Crop rotation and green manure cover crops are an
essential element in the success of no-tillage in Latin America.
Only those farmers that have understood the importance of
these practices are obtaining the highest economic benefits
from this system. Cover crops do not cost but will pay. When
practiced in monoculture or in double-cropping no-tillage
is an imperfect and incomplete system in which diseases, weeds
and pests tend to increase and profits tend to decrease. Adaptive
research in this area is the most important factor for making
no-tillage work—that is, enabling farmers to take advantage
of all the benefits of the system, including reduced weed
pressure and increased economic returns!
Research conducted in southern Brazil shows consistent reductions
in weed infestation with crop rotations in no-tillage and
conventional tillage (Table 2).
Table 2:
Number of weeds per m3 with and without
crop rotation in two tillage systems in Rio Grande do Sul,
Brazil (Ruedell, 1990, adapted by Gazziero, 1998)
| |
With Rotation |
Without Rotation |
| Occurance of weeds |
NT |
CT |
NT |
CT |
| Broad leaf weeds in wheat |
36 |
24 |
102 |
167 |
| Narrow leaf weeds in wheat |
17 |
30 |
41 |
44 |
| Broad leaf weeds in soybeans |
4 |
20 |
15 |
71 |
Good no-till farmers in Latin America use GMCCs and crop
rotations independently of the price situation of crops. Once
farmers have discovered the benefits of these practices they
don’t want to miss them. Sorrenson (1984), among others,
has clearly shown the economic advantages of using crop rotation
and the right cover crops. While many people still think that
when using GMCCs you are adding costs without getting anything
back, farmers especially in Brazil and Paraguay have learned
that economics of no-tillage can be substantially increased
with their use.
Research conducted by Kliewer (1998) in Paraguay has shown
that crop rotation and short-term GMCCs can reduce the cost
of herbicides drastically, to US$36.62/ha in the case of Crotalaria
juncea (52 days GMCC) and to US$37.39 in the case of sunflower
(57 days GMCC), versus costs of US$107.66 when only herbicides
and monoculture were used. Kliewer (unpublished, 1998) also
reported soybean yields after black oats of 2600 kg/ha without
using any herbicides at all. Weed measurements 96 days after
seeding soybeans showed 93 kg/ha of dry matter of weeds/ha
after black oats versus 7390 kg/ha after fallow. In the last
case, soybeans yielded not more than 780 kg/ha. Using a rotation
where long- and short-term GMCCs or cash crops are seeded
as soon as possible after harvesting the previous crop, or
after rolling down GMCCs with a knife roller, it was possible
not to use herbicides in no-tillage for as much as three years
in a row. In some cases when farmers are using crop rotations,
only eliminating weeds with a total herbicide before planting
is necessary without any herbicide application during the
growing season. If some weeds escape, they can be economically
controlled by hand hoeing.
Research conducted in Brazil has shown that black oats used
as a green manure cover crop before soybeans can increase
soybean yield by as much as 63% compared to soybeans after
wheat (Derpsch, et al., 1991).
Good knowledge about green and dry matter production and profitability
of green manure cover crops, how to fit them into different
crop rotations and what residual fertilizer effect to expect
of is essential for dissemination of their use. Several publications
have contributed to filling this knowledge gap, mainly in
Brazil (Sorrenson and Montoya, 1984; Monegat, 1991; Derpsch,
1991; Derpsch and Calegari, 1992; Calegari et al., 1992).
Lessons learned
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Steps
in no-tillage adoption
All too often we see that some farmers after hearing
about no-tillage buy a no-tillage machine. This
has led, in many cases, to failure in the application
of the technology. Only after acquiring good knowledge
about all the components of the system should
a farmer buy a no-till planter.
Several critical factors should be considered
before starting no-tillage. Therefore, we recommend
the following steps to farmers:
-
Improve
your knowledge about all aspects of the system,
especially weed control
-
Analyze your soil and if necessary
incorporate lime and correct nutrient deficiencies
-
Avoid
soils with bad drainage
-
Level the soil surface if
necessary
-
Eliminate soil compaction
using chisel plows or subsoilers
-
Produce
the highest possible amount of mulch cover
-
Buy a no-till machine
-
Start
on only 10% of your farm to gain experience
- Use crop rotations and green manure cover
crops to get the full benefits of the system
- Be prepared to learn constantly and stay up
to date with new developments
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One of the most fruitful lessons we have learned in the no-tillage
system is that farmers should, if possible, never leave the
land in fallow. In general fallow periods of only a few weeks
will result in weed proliferation, reduction of soil cover,
soil erosion and lixiviation of nutrients. If instead farmers
seed any crop as soon as possible after harvest, they will
reduce weed proliferation, increase soil cover and organic
matter, avoid soil erosion and the washing out of nutrients,
and improve soil biological conditions. After systematic research
with GMCCs in the late 1970s, a variety of crops have been
identified and are now available for use by farmers especially
in Brazil and Paraguay. Some of the winter cover crops are
black oats (Avena strigosa Schreb), rye (Secale
cereale L.), triticale (Tritico-cereale), oilseed
radish (Raphanus sativus var. Oleiferus
Metzg), white bitter lupins (Lupinus albus L.), vetches
(Vicia sativa L.), hairy vetch (Vicia villosa
Roth), chick peas (Lathyrus sativus L.), and sunflower
(Helianthus annuus L.). The most commonly used summer
cover crops are millets (Penisetum americanum L.,
Sorghum bicolor L, etc), crotalaria (Crotalaria
juncea L.), and lab-lab (Dolichos lablab L.).
Even plants that up to now have been considered noxious weeds,
like Brachiaria plantaginea, are used in the Cerrados
of North-Central Brazil as cover crops in no-tillage. The
Cerrados have only one growing season. Here farmers and researchers
have developed production systems where cover crops are established
immediately after harvest. If cover crops die in the dry season
it is not a problem as long as they have produced enough biomass.
In Southern Brazil and Paraguay conditions are such that some
cash or GMCCs can be seeded at any time of the year if soil
moisture is available.
GMCCs and crop rotation are key factors in the unprecedented
growth of no-tillage especially in Brazil and Paraguay. Linked
to the spread of cover crops is the use of a "knife roller"
to lay down the cover crops. This implement is inexpensive
and in many cases can be made locally or on-farm. It can be
pulled by medium-sized tractors or by animal traction and
has contributed a great deal in reducing herbicide rates in
the no-tillage system. The knife roller has become an essential
tool for managing GMCCs in many countries of South America.
Alternatively, steel bars can be welded on top of the discs
of disc harrows for the same purpose.
New developments
No-tillage is a dynamic system, so farmers should
be prepared to learn constantly and stay up to date with new
developments. New, cheaper and better herbicides and machines
appear continually, new cover crops are introduced, new research
results on fertilization, liming, varieties, management, diseases
and pest control, etc., are constantly published. We are learning
that no-tillage facilitates biological pest control. We know
that we should learn from organic farmers and introduce aspects
of biological farming into the no-tillage system. We have
to be humble and remember that there will always be more to
learn. There is great opportunity for every farmer to be creative
and to develop the system further.
Finally, we have to admit that all over the world farmers
adopt technologies because they are economic and are positive
to their pockets and seldom because they are environmentally
friendly. Therefore an economic evaluation of the system under
the different agroecological and socio-economic conditions
is essential. It is misleading to analyze the results of only
one or two cropping seasons. Instead an evaluation of the
whole system, with all its components has to be made, putting
value to timeliness, wear and tear on equipment, improvement
of soil fertility, reduced costs for fertilizers and pesticides,
environmental benefits, etc.
Thorough economic studies have been made by Sorrenson and
Montoya (1984) in Brazil and again by Sorrenson et al. (1997
and 1998) in Paraguay. The 1998 economic evaluation in Paraguay
was made on small farms, generally less than 20 ha, without
tractor mechanization. The study concluded that economic benefits
from adoption of no-tillage on 480,000 ha in Paraguay amounted
to US$941 million (Sorrenson, 1998). The same author claims
that "no other farming techniques have been shown to
have such a high impact on farmers’ incomes, reduce
their production costs and risks, and at the same time be
environmentally sustainable and generate very considerable
net social gains to society."
Rolf Derpsch is an international agricultural consultant
specializing in conservation agriculture, no-till, cover cropping
and on-farm research. Born in Chile of German parents, he
speaks six languages, has worked all over the world, and currently
makes his home in Asunción, Paraguay. From 1966 to
2001, Derpsch was employed by GTZ, the German Agency for Technical
Cooperation, where he became an early advocate of no-tillage
technologies. You can read more about his work and about no-till
farming at www.rolf-derpsch.com.
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