Frontiers in conservation tillage
Assessing the past, present and future of no-till
as a global conservation practice

By Rolf Derpsch
Posted April 14, 2005

A longer version of this paper appears in D.E. Stott, R.H. Mohtar and G.C. Steinhardt, eds., Sustaining the Global Farm - Selected Papers from the 10th International Soil Conservation Organization Meeting, held May 24-29, 1999, at Purdue University and the USDS-ARS National Soil Erosion Research Laboratory. Reprinted by permission of the author.

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.

 

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

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:

  1. No-tillage offered efficient erosion control under climatic conditions with high potential for soil erosion and degradation.
  2. Appropriate knowledge was available through research and development as well as farmers' experiences.
  3. There has been widespread use of cover crops for weed suppression (reducing the use of herbicides), organic matter build-up, biological pest control, etc.
  4. A consistent, positive message about no-tillage has generally been voiced by all sectors involved, private and public.
  5. No-tillage has been the only conservation tillage technology recommended to farmers.
  6. There has been aggressive farmer-to-farmer extension through farmers' associations.
  7. Publications with adequate, practical information were made available to farmers and extensionists.
  8. Economic evaluations using a system approach showed substantial, immediate economic returns for no-tillage, including no-till with cover crops and crop rotations.
  9. There have been no major forces against the system.
  10. 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

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

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

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:

  1. Improve your knowledge about all aspects of the system, especially weed control
  2. Analyze your soil and if necessary incorporate lime and correct nutrient deficiencies
  3. Avoid soils with bad drainage
  4. Level the soil surface if necessary
  5. Eliminate soil compaction using chisel plows or subsoilers
  6. Produce the highest possible amount of mulch cover
  7. Buy a no-till machine
  8. Start on only 10% of your farm to gain experience
  9. Use crop rotations and green manure cover crops to get the full benefits of the system
  10. Be prepared to learn constantly and stay up to date with new developments

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.