LATIN AMERICAN CONSERVATION AGRICULTURE NETWORK (RELACO)
FAO is promoting a change in the concepts and understanding regarding soil tillage and a reduction in the intensity and use of tillage equipment. It favours a greater use of conservation tillage techniques and related equipment and sustainable soil management practices. FAO has helped to disseminate information on the benefits of conservation tillage through education, technology transfer and input programmes.
To facilitate an exchange between participating countries, FAO supported the creation of a network, called Latin American Network of Conservation Tillage (RELACO), dedicated to the dissemination of conservation tillage systems. RELACO is a network of research and agricultural extension institutions, dedicated to the generation and transfer of technology on improved soil management and water conservation practices, with emphasis on conservation tillage.
How does RELACO work?
To function efficiently, RELACO depends on a regional co-ordinator, whose main responsibility is technical leadership and the administration of the network. The regional co-ordinator is supported by a technical committee consisting of specialists and experts of participating institutions who act as national co-ordinators of the network. The main function of the committee is to evaluate the execution of forthcoming planned activities of the biennial workplan. At the end of every biennium, the technical committee meets in a workshop where the Regional Co-ordinator for the following two years period is elected, and the venue for the next conference is chosen. Traditionally, members of the institutions organizing the actual workshop have been elected as the network co-ordinators for the next biennium.
History of RELACO
RELACO started its activities in 1986 with the aim of supporting national research institutions in technology generation, the dissemination of existing knowledge and methods for identifying soil management and conservation problems, and the evaluation of conservation tillage potential in the Chaco of Argentina, Bolivia and Paraguay. Venezuela joined the existing network in 1988, and in 1991 during a training course on Tillage Systems organized by The National Institute of Agricultural Technology (INTA), with the support of FAO, the Latin American Network of Conservation Tillage was founded. This course was held at the Sáenz Peña Agricultural Experimental Station (Province of Chaco, Argentina), and attended by persons from nine countries (Argentina, Bolivia, Brazil, Costa Rica, Nicaragua, Paraguay, Peru, Dominican Republic and Venezuela). With the joining of institutions from Chile, Columbia, Cuba, Ecuador, El Salvador, Honduras and Mexico, RELACO now has a membership of 16 countries.
Objectives of RELACO
The main objective of RELACO is to improve the utilization of soil, water and plant nutrients by generating and transferring tillage practices which prevent soil degradation. Despite the adverse socio-economic situation of farmers, the research and technology transfer promoted by the Network is gradually resulting in a shift from conventional tillage to conservation tillage systems. The Network also promotes an integral focus on management, which includes crop rotation, crop cover, the use of organic materials to restore soil structure and fertility, and the auxiliary practices of soil conservation which improve water and nutrient availability to crops.
Activities and results obtained by the Regional Co-ordinators of RELACO
National Institute of Agricultural Technology (INTA), Argentina
Ing. Agr. Roberto Casas, Director of the Institute of Soils of the Centre for Investigation of Natural Resources of the National Institute of Agricultural Technology (INTA) Argentina, was the first Regional Co-ordinator (1992-93) of RELACO. During the first biennium, RELACO provided technical assistance and stimulated the interchange of information between participating national institutes. A system of feedback and information exchange between participants, collaborators and co-ordinators of the Network was established through the publication of trimester circular letters. Successful examples of the validation and demonstration of tillage techniques were published. Teaching materials for a Training Course on Tillage Systems was published in FAO Soils Bulletin No. 66, entitled "Manual of Tillage Systems for Latin America" in November 1992. INTA and FONAIAP (The National Fund for Agricultural Investigation of Venezuela) agreed to organize the Second RELACO Biennial Meeting and Workshop on "Effects of Tillage Systems on the Degradation and Productivity of Soils" in Acarigua/Guanare (Estado Portuguesa, Venezuela), which is an intensively cultivated productive zone affected by soil degradation. The event was co-sponsored by the Food and Agriculture Organization of the United Nations, the National Experimental University of the Llanos Ezequiel Zamora (UNELLEZ) of Venezuela, and the International Society of Soil Science (ISSS).
The National Fund of Agricultural Research (FONAIAP), Venezuela
During 1994-1995, the Regional Co-ordination of RELACO was undertaken by Dr. Francisco A. Ovalles V. of the National Fund for Agricultural Research (FONAIAP) of Venezuela, supported by the Soil Resources, Management and Conservation Service of the Land and Water Development Division of FAO. The Venezuelan Network of Conservation Tillage was formed during this period and many circular letters and technical bulletins were published. Material presented at the Workshop, "Effects of Tillage Systems on Soil Degradation and Soil Productivity" in Acarigua/Guanare was edited by Ildefonso Pla Sentis and Francisco Ovalles, and published as Memoirs of the Second Biennial Meeting of Conservation Tillage. The Institute of Research in Agricultural Resources (CENIAP) of the National Fund of Agricultural Research (FONAIAP) of Venezuela, in its capacity as the Regional Co-ordinator of RELACO from 1994-95, and the Ministry of Agriculture and Livestock (MAG) of Costa Rica, agreed to organize the Third Biennial Meeting of RELACO. The event took place from 4-8 December 1995 in the Faculty of Agronomy of the University of Costa Rica (UCR), in San Pedro de Montes de Oca, and was co-ordinated by the MAG, with support from the Costa Rican Association of Soil Science and the Centre of Agronomic Research of the UCR. Venezuelan co-ordination, financed by FAO-RELACO, was in charge of inviting the foreign participants.
National Centre for Training and Communications for Development (CENCCOD), Costa Rica
Ing. Agr. Nils Solorzano, an official from the Ministry of Agriculture of Costa Rica was in charge of the Regional Co-ordination of RELACO during the biennium 1996-97. In this period, 64 professionals had attended a round table conference on the importance of conservation agriculture. The formation of National networks has also been promoted. At that time existed: the National Network of Conservation Agriculture (RENACO) in Costa Rica, the Venezuelan Network of Tillage, Water and Soil Conservation (REVELACO), the Network of Conservation Tillage of Argentina (RALCO) and the Dominican Network of Conservation Tillage (REDOLACO). RELACO supported various Mexican institutions to strengthen the Mexican Network of Conservation Tillage. An agreement of Technical Co-operation with Developing Countries (TCDC) has also been signed between Costa Rica and Brazil to cover topics such as conservation agriculture, conservation tillage and participatory planning, whilst an agreement between Costa Rica and Cuba covers organic agriculture and conservation tillage equipment. Finally, in co-ordination with Dr. Ramon Claverán of the National Institute of Research in Agriculture, Forestry and Livestock (INIFAP) Mexico, the fourth Biennial Meeting of RELACO was organized in from 17-20 November in Morelia, Mexico. The proposed theme was "Institutionalization of Conservation Agriculture".
National Research Centre for Sustainable Production (CENAPROS), Mexico
Dr. Ramón Claverán Alonso, Director of the National Research Centre for Sustainable Production (CENAPROS) of Mexico was elected regional Co-ordinator of RELACO for the biennium 1998-99. During the VIth meeting of RELACO in Morelia, Mexico the name of RELACO was changed from "Conservation Tillage" into "Conservation Agriculture" Network. The Mexican network for conservation farming was founded. As work programme for this biennium it was decided to obtain for the network a legal status as association, to charge a membership fee, to open a web site in the internet, to approach additional funding sources, organize more national networks and reinforce the present ones, co-ordinate projects and exchange experts.
ADVANCES IN THE UTILIZATION OF CONSERVATION TILLAGE IN LATIN AMERICA
So far, efforts on planning, research and technology transfer in conservation tillage in Latin America are giving expected results, though with varying degrees of success. The real contribution and potential of conservation tillage towards an effective and sustainable use of soils is indisputable, and can result in greater food security for the growing populations of Latin America.
ARGENTINA
Humid and Sub-Humid Regions
During the last two decades, soil degradation has increased at an alarming rate in the humid and sub-humid regions of Argentina. The main cause has been the use of clean fallow in the rotation wheat/second Soya crop. Conventional tillage using a disc plough, disc harrow or double disc harrow, results in soil free of weeds and crop residues, exposed to torrential summer rains.
To slow down the degradation process, a decision was made to change over from conventional tillage to conservation tillage. INTA (National Institute of Agricultural Technology), together with private institutions, technical advisors and companies supplying equipment and inputs are now involved in an intensive period of research and technology transfer related to conservation tillage.
Trials conducted by INTA at Marcos Juárez Experimental Station show that direct sowing increases the yields of wheat and the second Soya crop in rotation. Other benefits observed are: less soil inversion leaving a greater quantity of stubble on the surface, improvements in hydraulic conductivity, more efficient use of soil water, and higher soil organic matter contents.
In fact, direct sowing is an alternative technology that has aroused most interest amongst farmers in humid and sub-humid regions of Argentina. It is estimated that in the region producing wheat and Soya, more than 4 million hectares are now sown under different types of conservation tillage.
Semi-arid Region
In the semi-arid region, especially in Domo Agricola del Chaco, the main causes of soil deterioration are: cotton monocropping, intensive conventional tillage and erosive climates characterised by intense rains and strong winds between October and December, which coincide with the period of sowing cotton.
Faced with the problems of natural resource degradation and with existing technologies, the "Conservation Production Alternatives for Mechanized Systems of the Chaco Project" was launched in 1990, based on crop and crop-livestock rotations, pasture reseeding, reductions in the number of passes with implements, and the use of traditional green manure. The intervention strategy developed by INTA, functions through a strong agricultural extension component, on-farm field trials (adaptive experimentation), and the formation and promotion of farmer associations within which demonstrations of production systems are selected that permit natural resource conservation.
Trials conducted by INTA at the Sáenz Peña Experimental Station comparing conventional tillage system with minimum tillage and direct sowing have shown that conventional tillage produces considerable cotton seedling losses due to low emergence followed by death due to the destruction of the superficial soil structure. In contrast, direct sowing and minimum tillage result in greater seed emergence and lower plant mortality. Management of stubble on the soil surface, as obtained with direct sowing or with a "rough" seedbed obtained by minimum tillage, contributes towards higher plant densities per hectare.
In the 1994/95 campaign it was estimated that an area of 3 300 hectares was covered with directly-sown crops, of which 650 hectares corresponded to rice, 1600 hectares to Soya and the rest to maize, pastures and cotton. In Corrientes, there are about 6000 hectares of rice (10% of the total surface) under direct sowing, with minimal previous tillage just to eliminate the combine harvester tracks and to level the soil.
BOLIVIA
Semiarid and hilly region
In much of the Central Valley of Tarija in Bolivia, a large part of the natural vegetation has been eliminated as a result of agricultural activity, resulting in extensive areas showing advanced processes of soil degradation. Conventional tillage with animal traction (a pair of oxen) using a wooden plough, shallow ploughing and excessive pulverization, results in sub-surface sealing below the plough depth to form a compacted layer at 15-20 cm depth over successive years, which impedes water filtration and root growth. Soil compaction can also occur by animals grazing during winter months, although this type of compaction is more superficial.
Scarce crop residues are normally removed, leaving the soil exposed to the erosive effects of rainfall. This practice is typical of small farmers, faced with low quality natural resources in poor, degraded areas that are easily eroded, and results in subsistence levels of crop production. The limited availability of technologies adapted to these conditions is also a factor which affects yields and soil and water conservation, with repercussions on all the inhabitants of the region. In response to this worrying situation, the use of crop residues (stubble) as cover, minimum and zero tillage have shown that in this region of Bolivia, simple, management practices requiring low investment give encouraging results.
Sub-humid Region
The "Expansion Zone", located east of Santa Cruz de la Sierra, extending north-south from El Plato to Morgen Land colony, and west-east from San José to Rio Grande represents a new zone of great expectations and high potential for extensive agricultural development. This is reflected by the great influx of farmers and agricultural companies over the last 10 years, and a parallel increase in the area sown to crops.
Mechanized agriculture with excessive soil tillage that leaves few crop residues on the surface in the preparation of a "clean" seed-bed, and mechanical weed control, have resulted in compaction, crusting, reduction of soil organic matter and other soil problems that limit the productivity of very important agricultural zones in Santa Cruz.
Investigations on conservation tillage initiated in 1989, localized in different edapho-climatic zones of the department, have demonstrated that leaving adequate crop stubble on the soil surface is the foundation stone for the successful development of direct sowing. In general, the maintenance of a good protective cover, derived from previous crop residues or from a cover crop, offer multiple benefits to the system. The most important of these benefits are the control of water and wind erosion, improved capture and retention of rainwater in the soil profile, total elimination of crusting, better regulation of soil temperature, a notable reduction in weed incidence and improvements in soil fertility.
However, it is very difficult to maintain an adequate quantity of stubble in direct sowing, due to its rapid decomposition caused by climatic conditions that favour organic matter decomposition, such as high humidity and temperature, particularly in the summer. It is therefore necessary to plant green manure as an additional crop sown between the harvest of summer Soya or maize, and the planting of winter wheat. Amongst the green manure species which are highly competitive and/or effective for weed suppression are crotalaria (Crotalaria juncea), black Mucuna (Stizolobium sp. = Mucuna sp.), grey Mucuna (Stizolobium cinereum = Mucuna pruriens), Mucuna "barcina" (Stizolobium sp. = Mucuna sp.) and pearl millet (Pennisetum americanum = P. Typhoides); these species are characterized by rapid initial growth and cover the ground in a short time.
Vertical tillage is one of the systems that have been most easily adopted by Soya and maize farmers in the expansion zone. In fact, vertical tillage is being utilized by about 50% of the farmers. On the other hand, zero tillage has increased its area in a spectacular manner. In the summer season of 1994-95, 20 farmers started this system, and by the winter of 1995 the number had increased by 185%. The area sown under zero tillage in winter 1995 was 28,752 ha, compared to 22,000 ha in the 1994-95 summer season. Farmers who practice zero tillage use modern equipment, especially for herbicide application and sowing. However, it is important to stress that the transition from conventional to zero tillage is difficult initially. Therefore due to lack of experience, technical knowledge and awareness of the necessary precautions required to change from a conventional system to zero tillage. About 60% of the farmers changed from conventional to zero tillage directly, while the remaining 40% took precautions by carefully preparing their soils using a chisel plough or subsoiler to break up compaction horizons.
BRAZIL
Humid Region in Undulating Areas
The transitional tropical-subtropical climate in the southern zone of Brazil presents a great challenge to grain and forage production for sustenance, whilst preserving soils and soil fertility. Up until the decade of the 70´s the traditional system of intensive management (two harvests per year), using conventional clean tillage caused grave problems of soil degradation.
Between 1970-83, the state of Paraná introduced minimum tillage and direct sowing in order to promote a good soil cover, improve the productivity of beans, Soya, maize and rice, and reduce soil erosion processes. It also introduced crop rotation systems of grasses with annual crops in order to renovate the prairies.
Over the last decade, systems of zero tillage have been widely adopted by large farmers in Paraná and by small farmers in the state of Santa Catarina. The change from conventional to conservation tillage in Paraná and Santa Catarina has shown that erosive processes can be reversible if the farmers are willing to change their soil management system.
Initial implementation of conservation tillage has two basic requisites: (a) loosening compacted layers in the subsoil (e.g. the plough pan), (b) correcting aluminium toxicity and low pH within at least the upper 20cm. These requirements are achieved by applying lime to the soil surface, followed by deep tillage or ripping passing below the compacted layer. It is essential that no physical or chemical barriers exist in the soil's rooting zone, and it is important to eliminate rill erosion by levelling the surface. This should be followed by dense sowing of oats or a grass crop.
CHILE
Sub-humid Region in Hilly areas
The entrance of Chile into the global economy has provoked important changes in the production of annual crops. Since 1991, there has been a negative tendency in agricultural productivity due to the use of inappropriate tillage systems which intensify the natural soil degradation processes. Water erosion is already a grave, endemic problem in a great majority of soils in the Cordillera de la Costa (Alfisols) and the Andean lower mountain ranges. More than 75% of the soils used for rainfed cropping are affected by processes of soil erosion, and in the arid ecosystems of the north the soil cover fluctuates between only 0-40%.
As a consequence of the observed degradation problems, new tillage practices have been introduced into the coastal mountain range, which permit seeding without inverting, harrowing or disturbing the soil, so that seeds are sown through the residues of the preceding crop. These practices avoid the problems of water erosion, and eliminate the need for traditional conservation practices such as terraces and strip cropping.
Results of comparative trials on conventional and conservation tillage conducted in Chequen in the south of Chile, show that to date, the high investment required for zero tillage has given economically favourable results in comparison with conventional systems, and at the same time has reduced erosion and improved soil fertility. It was also possible to observe crop residues on the soil surface, which was not the case before the initiation of the intervention, and which has therefore helped achieve the objective of an increased cover. In addition, sowing by minimum tillage has enabled farmers to improve the supply of forage for animals, and the possibility to produce seeds for the next sowing.
The present situation on the use of conservation tillage in Chile shows that from Regions V to X the commercial practice of not inverting the soil, generally for sowing annual crops is less than 10 years old. Nevertheless, it achieved a great acceptance by entrepreneur farmers, considering that according to their experience, yields were not affected negatively, which implies less machinery use and greater flexibility in the sowing period.
The management of soils by zero and reduced tillage has increased at the rate of 4,000 hectares per agricultural season in severely eroded granitic soils in the VII Region, between
5,000 and 10,000 hectares in the VIII Region, about 60,000 hectares in the IX Region and about 10,000 hectares in the X Region. In these regions, most of the land under zero tillage, is found in the Pre-Cordillera, an agroecological zone which may be regarded as the most important area for food production, in the face of future changes in the demand for food, the result of global economic policies in the Southern Cone countries.
COSTA RICA
Humid Hilly Regions
In Costa Rica, the northern zone of Cartago is characterized by a system of intensive horticultural production, principally onions, and shows a high degree of soil deterioration from to erosion. The erosion is a consequence of tillage practices using disc ploughs and rotary cultivators prior to each crop planting. Land use is intensive with a minimum of two crops per year, and hardly any crop rotation is practised. Onion is a crop with few leaves, hence the soil remains largely uncovered throughout the entire crop cycle. In addition, the whole zone is dominated by slopes greater than 10%. The project MAG/FAO on promoting soil conservation, validated the use of chisel ploughs to reduce erosion, compaction and production costs. The lack of soil cover is one of the greatest problems in the entire zone. In the representative farms of the Pilot Area, farmers have reduced the number of disking, and especially of passes with the rotary cultivator type. Similarly preparing and sowing land on the contour with a gradient of 3% has been adopted by the farmers in the pilot areas. In addition, it has been observed that costs of using a chisel plough were much lower than those for conventional ploughing, and could be reduced even more by using fewer passes.
EL SALVADOR
Sub-humid dry Region
During the decades of the 70’s and 80’s, a new project on tillage and soil conservation was initiated by CENTA through the Agency of Agricultural Extension of Guaymango, located in the south west of El Salvador. The project started with the practice of "no burning" crop residues in the maize-sorghum system, which is most common in the Guaymango-Metalío area. The project objectives were: promotion of conservation tillage with "no burning of residues" in the maize-sorghum system; increase and maintenance of grain and residue production in the maize-sorghum system; improvements in the living standards of small farmers in the project area, and a gradual diminishing of degradation of the natural resources (water, soil and forest).
MEXICO
During the last 50 years, Mexico has suffered from
an accelerated deterioration of its natural resources as a consequence of agricultural
practices which do not take soil and water conservation into consideration. The
application of conventional tillage systems, the absence of practices such as cover to
protect the soil from erosive rain and concentrated overland flow, and the preponderance
of monocropping systems (maize-maize), are some of the reasons for soil losses in hilly
and steeply sloping areas.
The potential contribution of conservation tillage in Mexico has shown that it considerably diminishes soil erosion, and can reduce it almost to zero, and maintains higher water infiltration rates. In addition, there is a reduction in the number of weed species, the effect being most pronounced in systems with more than 60% residue cover. The possibility of including legumes in irrigated cropping systems with conservation tillage seems most favourable. Research has shown that legumes can add significant quantities of nitrogen to the soil - up to 130kg/ha, when included in a crop rotation. In contrast when the legumes are associated, they cause a reduction in maize yield without supplying any Nitrogen to the grain crop. Research has shown that zero tillage and chisel plough treatments reduce soil losses by 40 and 49% respectively in comparison with harrowing which registered the highest losses. Another important aspect related to soil cover and erosion is that soil losses diminish in proportion to the increase in crop cover. In the case of wheat, a crop with a high basal cover, erosion is reduced by 95% compared to the control, and is much more effective than maize which reduces erosion by only 52%.
In spite of the efforts made to introduce conservation tillage, the impacts have been much less than expected. Thus the area sown with conservation tillage in Mexico is 45,000 hectares, which represents only about 2% of the potentially cultivable lands, whilst the problem of soil degradation due to erosion continues to increase at an accelerated rate.
A factor which has limited the adoption of conservation tillage is the need to use crop residues for cattle feed, even when the farmer realizes the importance of crop residues for restoring soil fertility and reducing erosion losses. Investigators in Chiapas, in the Southeast of Mexico, found that 49% of the 443 farmers interviewed, who cultivate maize and maize-beans in lands of more than 40% slope, knew the importance of using residues, at least for returning a part of the soil nutrients extracted. Nevertheless, 87% of those interviewed had to feed at least one livestock unit, whether it is cattle, horses, goats or sheep.
PARAGUAY
Sub-humid dry Plains
The Chaco of Central Paraguay is a fragile ecosystem, which when badly managed can suffer irreversible damages. The agriculture of this region has been developing for about 60 years. The principle crops are peanuts, cotton, sesame and Euphorbia; with few winter crops included in the rotation due to drought. Soils show a constant reduction in productivity due to impoverishment caused mainly by monocropping, inadequate tillage and wind erosion. During the first few years, the soil is tilled by hand, and then by oxen and horses. Mechanization was introduced in the 70’s and the implements most used are disc ploughs of three or four discs and off-set disc harrows used with 75 HP tractors.
The cost of soil preparation is high, and from an economic view point it would be interesting to reduce the excessive tillage. Soil compaction is another negative effect, caused by using many machinery passes. The number of passes made by tractors are 13 for peanuts, 17 for cotton, 10 for Euphorbia, and 7 for grain and forage sorghum.
In order to reduce the number of tractor passes, investigations are being carried out to find species of green manure adapted to the climatic and soil conditions of the region, and which can be sown after groundnuts and cotton. In addition to the many benefits of incorporating green manure, it will provide a protective cover against soil erosion and subsequent degradation, and will reduce the number of operations required for winter soil preparation. In this way it would be possible to develop sustainable agriculture.
In Paraguay, the diffusion of conservation practices currently promoted by government and agricultural co-operatives, generally centres around those particularly involved in direct sowing, the establishment of permanent soil cover and an increase in soil organic matter. The increase in the area under direct sowing has increased from 20,000 hectares in 1992 to 230,000 hectares in 1995. In absolute terms, comparing with similar regions in neighbouring countries, the figure has little significance, but in relative terms, it signifies an increase of 15.3% of the total area under mechanized cultivation, a figure unmatched by any other conservation practice recommended in Paraguay. Factors which favour the adoption of this tillage system are its profitability and access to herbicide technology.
PERU
Humid Tropics
In continually cultivated Ultisols of the humid tropics in Yurimaguas (Loreto), with an average annual rainfall of 2,200 mm, the potential for soil erosion is high.
Results of investigations conducted at the Experimental Station of Yurimaguas, showed that soil bulk density at 0-10 cm depth, in treatments where subsoiling along the crop row had been applied, increased slightly compared to measurements taken before the subsoiling treatment was applied. The change in bulk density at 10-20cm depth was not significant for subsoiling treatments without tillage, but increased significantly in subsoiling treatments with minimum and conventional tillage. This must be due to the subsoiler loosening the soil up to 30cm depth, and when subsoiling was not used, compaction occurred due to the continuous weight of the disc harrow. Also, with no tillage, the soil surface was protected from the direct impact of rain drops, resulting in increased infiltration, reduced runoff and associated plant nutrients.
Since there was no soil disturbance in the zero tillage treatments, there was an accumulation in the superficial layer (0-5cm) of P, Ca and Mg - elements less mobile than potassium which is easily lost, Also, crop residues were left as a surface cover which prevented soil loss through runoff.
Yields of Soya were significantly superior in treatments with no tillage, with or without subsoiling, compared to yields with conventional tillage without subsoiling.
Considering the average yields from nine maize, and three Soya seasons, significant differences were observed between with and without subsoiling, regardless of the type of tillage practice for maize, but not for Soya. Perhaps with a longer period of evaluation a clearer picture may emerge.
Finally, significant differences were also found in tree cover diameter and height of Inga edulis. The effect of zero tillage with or without subsoiling was 50% higher than for conventional tillage after six months growth. This effect of treatments on growth rates signified that fallow periods should be much longer, as in six months it was estimated the trees should have an average height of two metros, which is the normal growth of a secondary forest.
VENEZUELA
Sub-humid Plains
For many years in Venezuela the use of high power tractors with implements for superficial soil preparation (harrows), has been a common practice. This has created serious problems of superficial and subsurface compaction, and has also accelerated other soil degradation processes, such as erosion, sealing and superficial crusting.
In response to the above-mentioned problems, numerous trials comparing direct sowing with conventional tillage have been implemented in various parts of the country, to evaluate yields and crop development of maize, sorghum, and Soya over a period of two years. Also, demonstration plots have been established in farmers’ fields to introduce direct sowing and minimum tillage in diverse basic grain-producing regions of the country.
In the Central Plains, a region with great agricultural potential, an accelerated increase in direct sowing has been observed, and at present there are about 50 seed drills suitable for direct sowing. This situation suggests a considerable increase in the area under direct sowing in future years. However, it is expected that the increase will be gradual, as work is needed to build up confidence amongst the producers’ leaders, to enable them to dominate the technology better. It should be noted that some operational problems have already arisen.
In the Central Plains, the potential for direct sowing in minimising and in some cases eliminating the negative effects of drought has been studied since 1988. Research projects designed to evaluate the effect of existing cover in conservation tillage systems on temperature, humidity, infiltration and other physical soil characteristics are being carried out. In parallel, an evaluation of nutrient dynamics, the efficiency of nitrogenous fertilization and the control of weeds are being implemented. Work in this zone also involves the adaptation of conventional equipment to direct sowing, as the costs of acquiring special equipment are very high, and represent a serious limitation in the adoption of these technologies.
In the Western Plains, FONAIAP has been doing a follow-up study on a maize-beans rotation, and the response of different crops to different tillage practices. Recently, through an agreement between FONAIAP-PROCITROPICO, a project evaluating management alternatives for the sustainable production of annual crops in the Western Plains has been initiated. In parallel, the Post Graduate Soil Science Department of the Faculty of Agronomy of the Central University of Venezuela (UVC) and its mechanization section has been conducting trials on tillage systems for different crops (maize, sunflower, sorghum), which measure and evaluate variables such as soil, crop, soil-machine relationships, operational problems and cost-benefit ratios amongst others.
In the region of Guayana, investigations on tillage systems are just beginning and there are only references to some experiences in the commercial field (1,000 hectares). In the zone of Paragua there are some encouraging results, but with operational and management problems which must be solved.
As a result of the
above mentioned efforts, farmers in Venezuela have been accepting conservation tillage,
though with caution. It should be pointed out that in the last few years there has been
great acceptance of direct sowing by entrepreneur farmers, given that this implies less
machinery use and allows greater flexibility in the time of sowing. At present, the total
area under conservation tillage represents about 20,000 hectares, of which 16,000 hectares
are in the Central Plains and 2,000 hectares in the Western Plains. Some 2,000 ha also
occur in the Oriental Plains with crops such as maize, sorghum and Soya, and with
technical advice provided by some institutions. Satisfactory results have been obtained,
as the yields are equal to or higher than those obtained by conventional methods. It
should be stressed that in all the zones, the majority of the area is sown to cereal crops
such as maize-sorghum.
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