Indiscriminate and immediate exploitation was decisive in the different agricultural regions of the Paraná since the beginning of colonization. Most often, the natural vocation of areas was not respected, thus speeding a degradation process by water erosion and a decrease in organic mater and nutrients in the soil. 

Until 1990 only a few examples of no-tillage with small farmers in Latin America were found in the literature. Since then a number of projects have been carried out and many were presented in 1996 at the II Latin American Meeting on No-Tillage On Small Farms. According to FAO, approximately 4 million farms in Brazil use animal traction combined with human traction. These farms are characterized by family labor, animal traction, limited natural resources, unsuitability for intensive agriculture, high slope steepness, shallow soils and low natural fertility. Since 1985, the Iapar developed no-till technologies with animal traction such as the direct sowing-fertilizing machine (Gralha-Azul), in addition to technologies for the management of low fertility soils and for weed control in small farms. In 1991 on farm experiments were established with the aim of: a) verifying technical and economical factors that restrict the adoption of no-till system; b) monitoring the generation and technological adaptation process; c) evaluating ecological, technical, economic, and social sustainability of no-tillage systems in small farmers. In 1993, the small farm no-tillage project started with the participation of farmers, extension, research, and agricultural industry. The project resulted in an improvement of animal-drawn no-till implements for the management of the system, better labor distribution during the year, superior maize and beans yields, varying 78-106%, respectively, compared to conventional systems and positive net income and system adoption by 75% of the farmers involved in the project. The results show that the no-tillage system is technically, economically, and socially viable for small farmers, and an important tool towards small farm sustainability. 

The No-tillage system, entails using different species of green manure, dry matter crop residues, and crop rotation as fundamentals in the structure of rational and sustainable management, mainly in annual crop areas. The systematization of the areas through work in hydrological micro basins and also in no-tillage today occupies more than 3 million hectares in Paraná and estimates show that the No-Tillage covers close to 8 million hectares in Brazil. The results obtained throughout the years in Paraná and other parts of Brazil prove that green manure, as part of the productive systems preferably in no-tillage areas (No-tillage), are very economically feasible as well as ecologically sustainable; proving not only greater crop productivity, but also conservation, maintenance and/or recovery of soil fertility. In addition to this, they promote economy with nitrogenous fertilizers (leguminous plants), greater biologic balance in the soil, decreasing the effects of pests and or disease; in other words they represent a very promising way to manage soils tending to sustainability. 

The concern over preserving soil and water in Brazil wasn't a priority until the seventies. Perhaps due to the predominant systems: perennial crops and pastures, erosion wasn't so severe and hadn't created such interest; therefore it wasn't considered a priority problem until the so-called industrialization phase and agricultural intensification in the country. With the progress of areas with yearly crops, motomechanization, (which practically doubled in the Paraná in the seventies) and in the face of practically no conservation technologies, the accelerated erosion process and the growth of agriculture served as the framework for a new phase of soil and water preservation in Brazil in the seventies. 

Given the challenges imposed by the management, use and conservation of natural resources in the State of Paraná, Brazil, as years went by it became necessary to join efforts and systematize global integrated actions, capable of answering to different and complex demands through the use of efficient techniques in all the phases of the process. 

Happily, this situation began to change, mainly through relevant results in research, together with the rural extension work to help many growers adopt new practices to manage and conserve the soil. 

In Brazil, No-tillage system began more specifically in the state of Paraná at the beginning of the seventies, with a pionner farmer. The main objective was to control erosion in areas where soybean and wheat were intensively cultivated in southern Brazil. Afterwards, corn also began to be cultivated under this system. After this the researchs system started with experiments and also trying to improve this system according different production systems in South Brazil. 

According to data, more than 6 million (M) hectares are cultivated with summer species, areas that to date (1996) continue with the same trend: with soybean (2.5 M), corn (1.85 M), beans (470 thousand), cotton (98 thousand), irrigation rice (17 thousand), dry rice (80 thousand hectares) and others, sugarcane, cassava, coffee, fruits, etc. 

Approximately half this area remains uncultivated in the autumn/winter, though last year (1996) wheat was planted in 1.3 million hectares. In addition to this diversity of exploitations, the historical occupation in several economical cycles and the recent transformation of agriculture (in the seventies), betrayed by the urban-industrial development of the country contributed to this great variance. 

The absence of adequate occupation planing and use of the Paraná State lead a dramatically decreased tropical and subtropical forests (from 84% to 24% in 1965 and less than 10% to 1984) with agriculture covering both able as well as marginal areas. 

At present, there is a constant concern on the part of most growers to find appropriate global planing for soil exploitation and use, considering maintenance and/or recovery of fertility levels and productive capacity, balancing organic matter and preserving natural resources. 

Many of the results obtained by researchers and the practices of growers in different parts of the world show that the minimum disturbance in the soil and a perfect mulch on the surface made-up of growing plants or their residue, are effective ways to protect and restore the productive potential of the soil. 

1. Soil Management Methods 

In different parts of the world, researchers have proven that good coverage with plants or plant residue is an extremely important factor in protecting soil against erosion (Hargrove, 1982, Unger, 1994). 

When using traditional management and planting methods, soil can be protected by plants even in the most advanced stages of development. In general, primary management is achieved by plowing (tilling), which buries plant residue and leaves, leaving the soil naked and vulnerable to heavy rain. In Europe because of its low rain intensity as well as favorable topography and soil characteristics, this management system hasn’t caused such severe trouble. On the other hand, the use of these cultivation methods in heavy sloped areas in the tropics, undergoing heavy rainfall, has caused severe erosion and a dramatic loss of fertility in many farming areas (Derpsch, 1986). 

a) The Conventional Method 

The process of soil erosion is substantially influenced by management practices. In south, the standard method of the conventional system is basically: 1) (plowing with discs or harrows), and 2) rollers to break-up the soil and prepare the bed. When this system is followed correctly and tillage isn’t excessive, it causes less erosion damage than the traditional system (heavy rollers that barely penetrate 10-15 cm of the soil profile, leaving a small, thin and disaggregated superficial bed on the soil). Losses of between 10 and up to 40 t/ha/year of soil were observed under this system (Sorrenson & Montoya, 1984). 

b) Minimum Tillage 

Normally the soil surface is not totally disturbed in this system, which can be used chisel plow (animal or tractor traction), or some times small holes are opened by special implements, that in general allow a great part of mulch, residues of green manure or weeds ( 40- 70 %) remain on the soil surface. The major part of the soil surface remain undisturbed. In many cases is used in steep areas with animal traction. More than 70% of the area cultivated with soybeans and wheat which is not in no-till system grow in minimum tillage. 

c) No-Tillage 

No-tillage is the only planting method that makes it possible to keep soil covered with plant residue or developing plants all year long. 

Significant interest on the part of growers and progress in the No-tillage system and minimum cultivation in the USA has motivated the USDA to make projection for the following years (USDA, 1985). According to these projections, maybe more than 50% of the cultivation areas in the USA will be using the No-tillage system by the year 2010, and tillage and other conventional methods will be reduced to less than 5%. Estimates show that more than 17 million hectares have been seeded in the USA in the year 1996 (William Hargrove, personal communication, 1996). 

Thus, this system integrated or combined with mulch-producing plants and adequate crop rotation are the most efficient production systems that should be developed in tropical and subtropical conditions since they substantially reduce soil loss, increase soil fertility, crop yield and make continued soil use sustainable. 

The great challenge in No-tillage is to harmoniously balance and appropriately organize all the different components: that is to identify weeds in the field: choose if necessary, the right herbicides to be used and see to their correct application; use fertilizers, as well as green manure mulch crops) rationally, and rotate crops. In order to have an appropriate no-tillage system, continuous observation of the field is fundamental: watch plant development and constantly monitor changes in the physical, chemical and biological characteristics of the soil. A grower, therefore, needs good training and management skills. 

2. No-tillage in small farms : Iapar's researchs 

A few experiences has been related in Brazil and also abroad about the viability of the no-tillage practice by small farmers. Generally they are occupying areas with low soil aptitude intensive labor family use and also animal traction, finding in the no-tillage system a important alternative to save labor, improve soil conservation process and then decrease production costs. 

According to Araújo et all, 1991 some tentatives to develop mechanical implements were carried out by IAC (Instituo Agronomico de Campinas), ACARESC-SC and also by a factory from Curitiba-PR that developed a direct no-tillage machine which was projected by ITA (Instituto Internacional de Agricultura Tropical) (Schmitz,1988). Despite of this almost nothing was did to improve the use of no-tillage in small farmers. Starting in 1985 with a Research Project, the Agronomic Institute (Iapar) developed a no-tillage machine "Gralha-Azul" to improve the no-till system for smallholders in Paraná State. 

2.1 Experimental Station Plots 

Starting at 1985 testing beans and corn in no-tillage system with the Iapar no-till machine, after 5 harvests the results showed the needy to introduce changes related to soil fertility, green manure species in the crop rotation system looking for better conditions crops development. 

So, new experiments beginning at 1990 are been conducted to evaluate the effects of no-tillage including black oats mixed with common vetch, raygrás mixed with Ornithopus and velvet bean (Araújo et all.,1991). 

The results obtained are showing that: 

1. After 2 cuts the cover crops evaluated presented good mass production to implant the no-till system;
2. The cover crops were managed by knife roll and herbicides (handing spread);
3. The Iapar no-till machine "Gralha-Azul" presented a good performance cutting the straw, and also distributing the seeds and fertilizers on the soil, promoting a homogeneous plants developing.
4. Comparing with conventional system (plowed plots) were need 2 weeds handing control in the beans cycle, conversely in reason of alellophatics straw effects only one control operation was need in the no-till system.
5. In general the no-till treatments showed better plants development and also earlier soil cover than conventional system.

Another experiment evaluating soil losses showed the erosion effects reduction by some tillage systems (Table 1). 

Annual Rainfall Average during 4 years evaluation: 967,5 mm. 

Source: Araújo et all. 1991. Iapar, Ponta Grossa-PR. 

The soil losses were reduced in more than 90% in no-till system when compared with moldboard. 

2.2 Small farms Test/Validation Process and No-tillage system applied to Predominants Production Systems: 

In the studies conducted in farmers areas were applied the Iapar research methodology in Production System integrating the farmers evaluation in the testing/validation process. The no-tillage system is a tremendous dynamic system that leads a very strong change not only in the soil management process but also in the farmers behavior. The traditional costume and repeated practices plowing the soil every year need to be changed for a system which presents different challenges. One of the main aims to be considered for attain the no-till success is the constant monitoring soil properties and also many important aspects that need to be followed like a weeds infestation, soil compaction process, no-till machine adaptation, soil fertility dynamic, definition and management of cover crop and crop rotation. 

The results are showing that is factible the use of no-till system to small farmers meanwhile the studies and evaluation/validation need to be continued. Many challenges and advancing in weeds control, cover crops management (knife-roll, herbicides), soil fertility etc. need to be continuously evaluated and also monitored by the small farmers testing/validation technologies process. 

The crop rotation system used by small farmers in South Brazil, is according to soil, climatic, technical and economical factors. In the majority of the farms basically comprise: 

1) In the Fall/Winter season: oats (mainly black oats), vetches (common and hairy), oil seed radish, rye, lupin(white and blue), raygrás; many farmers leave in fallow, a few farmers number use wheat cash crop.

2) In the Spring/Summer season: corn, beans, tobaco, onion, garlic, potatoes, rice, cotton, etc. A very small group grow soybean crop. 

To maintain the no-till system is fundamental the use of crop rotation (Darolt, M. 1998) that will contribute to better soil equilibrium decreasing the insects and  disease effects and also diminishing the weeds infestation. 

Many times when the tabaco is the main crop the fertilizer residues are used planting 2 beans rows or 1 corn row in each tabaco planting row (is possible to use the handing machine "saraquá"or the no-till machine). There are some farmers, for example Mr. Rolando Ristow in Ibirama-Santa Catarina State, that use corn intercropped with mucuna which is sowed in the flowering corn stage and after corn harvested mucuna continue growing sometimes joint with a grass- Brachiaria plantaginea until the next Spring when is killed by knife-roll (or frost in the winter) and no-till tabaco are planted in small holes. This system are improving the tabaco and corn yield and also decreasing production costs enhancing the farm net income. 

There are some green manure options that can be used in Summer season like mucuna (Stilozobium spp), Crotalaria sp.(juncea, spectabilis, mucronata, ochroleuca, etc.), pigeon pea (Cajanus cajan), jack bean (Canavalia ensiformis), cowpea (Vigna unguiculata) etc. which promote a high nitrogen content to the system. Other species like Penissetum americanum, also can be very useful to mulch production, covering the soil and increase soil humidity and also effective in weeds control. 

Another option used by small farmers in Paraná State is the spontaneous vegetation grow that are formed mainly by Brachiaria plantaginea which will develop during the corn grow season and after will be killed by herbicides promoting a important mulching layer (4-7 tons of dry matter) which will be very important to no-till system and useful to planting beans, corn, cotton, soybeans, etc. 

3. The Results of the No-tillage System Including Green Manure and Crop Rotation 

With the practice of the No-tillage system and continually mulching soils with vegetal residue, soil losses due to erosion can be considerably decreased (Triplett et al., 1968; Lal, 1975; Wilson, 1978; Derpsch et al. 1991; Calegari et al., 1994). 

Assessments carried out by Calegari (data not published) on a soil with the following chemical composition: pH=4,7; Al³⁺=0,17 meq; Ca²⁺=3,5 meq; Mg²⁺=2,04 meq; K⁺=0,42 meq; %C=2,5 and P=3,0 ppm, in the southwestern region of Paraná (Pato Branco) are showed on Table 2. 

• Higher corn yields were obtained on vetches, blue lupin, and sweet pea.
• The no-tillage presented in the majority of the cases higher corn yield than conventional tillage.
• In general the corn planted on legumes cover crops presented low response to nitrogen application, conversely grasses areas and also fallow presented higher nitrogen response.
• The favorable tendency shown by the results achieved agrees with the data obtained by Paraná growers who use green manure, crop rotation and No-tillage.

They also prove that white and blue lupine, when cultivated before corn, can provide the equivalent to 90 kg/ha of nitrogen (Derpsch & Calegari, 1992; Calegari, 1995). 

The experience of a farmer in the Agripastos Farm in Palmeira, Paraná has shown that after 18 years of cultivation and management, the use of fertilizers decreases significantly, while grain yields increase under the No-tillage system as opposed to the conventional system (1 plowing and 2 turns with disc harrows). 

Table 2 . Corn yield (Ag-513) (kgha^-1 ) after winter crops. Pato Branco-PR Experimental Station. Average of 3 replications. 

The results are showing that with time, no-tillage leads to better conservation and improvement of all soil characteristics, thereby causing reduced fertilizer use, increased crop productivity and, consequently, greater profits from the property. 

4. Considerations on the Use of Technologies for Agricultural Development - towards Sustainability 

Old World experience has shown that the abundance of natural resources leads individuals to immediate actions. In contrast, scarce resources stimulate economical rationality and concern over predictability; in other words, responsible actions for environmental preservation both present and future. 

A clear example of the negative impacts of different agricultural technologies is soil misuse which reduces productivity. The estimates of EMBRAPA (Empresa Brasileira de Pesquisa Agro-pecuária; Brasilian Agricultural Research Firm), SNLCS Serviço Nacional de Levantamento e Conservação de Solos; National Soil Survey and Conservation Service) showed that application of the technologies available for soil conservation to control erosion in the South Central-South, and Central-West regions of Brazil, could avoid losses in 1992, of up to U$ 110 billion, in soil calculated as fertilizer equivalent (Vergara et al., 1991). 

Improving soil use and management processes is a way to keep families in the farming activity in a sustainable manner compatible with socio-economical resources. 

To guarantee long-term productive, competitive and sustainable agroecosystems, we must undoubtedly seek systems that contemplate, through biodiversity production diversification in time and in space, nutrient recycling and recovery and/or conservation of the physical, chemical and biological properties of the soil. Therefore, integrating duly systematized practices considerably helps improve not only agriculture as a whole, but also the socioeconomical conditions of rural growers. This means that it is crucial to environmentally plan agriculture in places where it has greater chances of success, and where agroecosystems with their self-control mechanics will act decisively to maintain acceptable dynamic balances in production and environmental quality. 

The No-tillage System leads to better work distribution throughout the year, which results in the elimination of soil tilling, harrows and mechanical control over weeds. This condition will provide more time to arrange, plant and manage different activities for better land diversification. With this system there is a significant reduction in soil loss, fertility improves, crops yields increase, there is greater production stability, in addition to the possibility of permanently using the land, thus proving that it also contributes to agricultural system sustainability. 

Bibliography 

Appendix

TABLE 3. Chemical composition of different cover crops used to green manure and animal food. 
 

Source: Adapted by Gallo et al., 1974, Kluthcouski, 1982; Calegari, 1982 and Chaves, 1989; cyted by Calegari ,1995. 

Agronomic Institute of Paraná-Iapar, Rod. Celso G. Cid, Km 375, CEP-86001-970, Fax: 00 55 43 376 2101,
Email:asoiapar@pr.gov.br , Londrina, Paraná, Brazil