EUROPEAN SOIL BUREAU RESEARCH REPORT NO. 7
Farmer classification. An approach to soil qualityin Murcia, SE of Spain
ANDRADE-LIMAS1 Elizabeth, FAZ-CANO Ángel2, GARCÍA-FERNÁNDEZ Gregorio2 & ARNALDOS-LOZANO Raquel2 1División de Estudios de Postgrado e Investigación. Universidad Autónoma de Tamaulipas, México. E-mail: eandrade @uamac.uat.mx 2Departamento de Producción Agraria. Universidad Politécnica de Cartagena, Murcia, España. E-mail: [email protected]
Abstract There has been very commonly an absence of correspondence between modern systems of soil taxonomic classification and the agronomical qualities of the soils. For this reason, this study has resorted to tapping the knowledge of the farmers that know best these agronomical properties in a practical sense, in order to obtain an agronomical classification of the soils. This rural classification has been determined for three typical agricultural zones near the Mediterranean coast of Spain. Four types of soils located in the study area and characterized according to the World Reference Base as Luvisol, Calcisol, Regosol and Fluvisol, were differentiated on the basis of physical and agronomics characteristics into 8 different classes according to the local farmers. The names given by the farmers, which refer to some distinctive feature of the soil’s physiognomy, are the following: "black", "mud", "red", "slate" or "sluggish”, "coloured ("red") or "moyas", "sand", "smooth" and "hard" soils. To this effect, this system exhibited a very high knowledge of the physical, chemical and agronomics properties of the soils. In a sense, this rural classification can be very helpful for a better knowledge of the soils, and to establish more effective technologies for the management and conservation of the agricultural lands.
Keywords: rural soil classification, ethnoedaphology, soil quality.
Introduction The Region of Murcia, located in SE Spain, has a semiarid climate that determines sparse vegetation and a high rate of erosion. It has been formed by a complex geological process (Arana Castillo et al., 1999). These particular geological conditions have given rise to prevalence of a mining industry in the region. The semiarid landscape of the Spanish South-east constitutes one of the European enclaves where the fingerprints of geological processes can be more clearly observed (Arana Castillo et al., 1999).
Under these environmental conditions, a variety of soils have been formed a long thousands of years, with well developed profiles and differentiated horizons. Inside the studied area, four groups of soils have been found (FAO-ISRIC-ISSS, 1998): Luvisols, Calcisols, Regosols and Fluvisols (Alías Pérez et al., 1986).
Most of these soils present a great agricultural potential, and they has been traditionally used for agriculture for centuries. Nevertheless, the traditional use of them have been altered since two decades ago, due to the construction of a big hydraulic system that has made possible the irrigation of thousands of hectares, which previously were devoted to rain fed crops. On the other hand, and due to the mining activity, many soils in the Region of Murcia have been, directly or indirectly, affected by this activity.
Agriculture always implies the modification to a smaller or greater extent of both physical and chemical properties of soils. In SE Spain, where agriculture is one of the most intensive in Europe, the lack of
An approach to soil quality in Murcia, SE of Spain. Andrade-Limas et al.. 157 EUROPEAN SOIL BUREAU RESEARCH REPORT NO. 7 rainfall and the increase in irrigated crop cultivation due to external demands has sometimes led to the use of irrigation water with a high salt content. Incorrect or intensive ploughing and excessive use of agrochemical compounds are other features that may lead to soil degradation. Consequently, soils of these agricultural areas are exposed to a very high erosion problem, and sometimes to a high salinity level. This has led to the plantation of salt-resistant crops in places.
Some mineralogical, physical and chemical properties of the soils have been considered, which have served for its classification in the World Reference Base (FAO-ISRIC-ISSS, 1998). In this respect, it is convenient to highlight the lack of correspondence between the agronomical qualities of soils of similar typology, which seems to be related with the lack of detail and the technical limitations that the proper system of classification presents. Another common situation solved by this farmer’s approach is when the investigator tries to classify a soil and faces a scarcity of information.
The present work had as general aim to demonstrate the usefulness of the rural knowledge on the different classes of soils placed in the Region of Murcia, as a frame of reference for the macromorphologic characterization and for the knowledge of use and management of these soils facing its conservation.
Materials and methods
Location of the studied area The present study was realized from February to April 2001, in three clearly delimitated stands sited around areas of Cartagena and Murcia city (SE of Spain), close to the Mediterranean sea. These different places were located in the central and east part of the Region of Murcia, two close to the locality of Cartagena and one near Murcia city, were considered.
In three different typical agricultural areas of Murcia, SE Spain, an ethno-edaphological study has been carried out. The management of these soils was quite different in each case: dry lands in La Azohía (Table 3), drip irrigation in El Beal (Table 2) and flood irrigation in the Huerta de la Vega Media del Río Segura (Table 4). These three areas were selected because the farmers have traditionally worked these soils using traditional land management and the obtained production is used for the family consumption. Likewise, the land uses are representative of the different forms of traditional management of the soils in the Region of Murcia.
The used methodology recognizes the existence of the empirical knowledge of the use of the natural resources, which has allowed to the peasants to establish an environmental nomenclature, which is neither commercial nor technical, but has a semantic soundness to name to the soils.
The climatic characteristics of this area are determined by its geographical situation in the south east of the Iberian Peninsula characterized by summer drought, scanty cloud cover and a high index of radiation. Physiographically there is a big contrast between the mountainous –forest- and the plain –agricultural- areas, so that vegetation changes depend on the climate and the relief (ITGME, 1999). Precipitation ranges from 200 mm to 300 mm, and temperature averages 18 °C throughout the year.
The agriculture of the zone is of great importance with crops such as almond tree and cereals in dry lands, and vegetables as potatoes, cabbage and pepper among others, and irrigated fruit trees such as the lemon tree, orange tree, peach and plum tree. In rain fed lands sheep keeping was of great importance, principally ovine and caprine production.
Field and laboratory work Several soil types were located in each study site (Table 1) according to the rural classification system of soils (Ortiz et al., 1990). It includes open interviews to the farmers joint with a direct observation in the field and complemented with the use of air photographs, edaphology maps, topographic maps and plans of the communities. Besides, conventional soil profiles classified by World Reference Base soil classification system (FAO-ISRIC-ISSS, 1998) were used for comparison purposes. The knowledge of the soil resource generated by the farmers, based on his traditional experience, leads to a better and more practical agronomic denomination. This is a rural classification of soils or ethnoedaphology (Ortiz et al., 1990).
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The guide of interviews carried out included questions about the sowed surface, types of farming, ways of sowing, types of fertilizers and plants that are used (forage, medicinal, ornamental), labors of farming, types of lands and its management. Fields tours were realized to locate the information, and to establish the boundaries of the different classes of soils in its plots. In the second stage, several representative points were selected for every study locality (from two to three per class). Profiles were realized for its field description, according to F.A.O.-I.S.R.I.C. (1990) guidelines.
Results and discussions Data related to the description of the different soil types according to the rural classification (Ortiz et al., 1990) are presented. An essential part of this work has been the use of farmer’s knowledge as an information source. When they were contacted it was important to look for expert farmers, with good field knowledge. The process was developed in a soft way, with no pressure at all and in a spontaneous way to enable a quiet conversation. They were in advance informed about our interest in their rural knowledge about the different soils qualities, and about alternative management and conservation techniques of the soils.
Using the ethnoedaphologic methodology, soils were classified in each studied site, having in account the interaction between the different soil types and its uses and management techniques. Classification was done to a plot level according to agricultural, livestock and forest production criteria. In this respect, a significant relationship has been found between the soil type and its management, and the soil use and the soil quality. Table 1 presents the data about the different soil types found following the rural classification of soils in three localities in the Region of Murcia, to the southeast of Spain. Eight soil classes according to the methodology published by Ortiz et al. (1990) were found: “black”, “mud”, “red”, “slate”, “reddish o moya”, “sand”, “smooth” and “hard” (Tables 1, 2, 3 and 4). These correspond to just four soil groups according to World Reference Base system (FAO-ISRIC-ISSS, 1998): Calcisols, Luvisols, Regosols and Fluvisols at the Reference Group level.
On the base of previous studies on these soils (Alías Pérez et al., 1986), in all cases the values of pH were lightly over 7.5-8, for what it is a question of soils lightly basic, whereas the values of salinity, measured as electrical conductivity, range around values of 1-2 dS m for the localities of El Beal and La Azohía, and of 3-5 dS m for the locality placed in La Vega Media del Río Segura. Table 1: soils types and taxonomic equivalence in the studied area of Murcia, Spain. Study site Soil type World Reference Base (1998) equivalence El Beal Black Calcisol A-Ck or Fluvisol Mud Fluvisol or Calcisol Red Luvisol A-Bt-Ck La Azohía Slate Regosol A-C Reddish o Moya Luvisol A-Bt-Ck Huerta de la Vega Media del Río Segura Sand Fluvisol A-C Smooth Fluvisol A-C Hard Fluvisol A-C
On the map obtained from the photointerpretation, using also the results of the field and the morphological observations, there can be seen an excellent correspondence between both methodologies, rural and taxonomic. Our results, show than the knowledge of the land and terminology used by traditional farmers do not mean an inadequate definition of the land. It has been corroborated with conventional soil classification methodology. Tables 2, 3 and 4 show different types of soils found by means of the rural classification of soils, in three communities of the Region of Murcia, Spain.
Soil type 1: Black Lands Black lands are identified by its grey and dark colour of the surface and a strongly darkish stratum below 30 centimetres depth. These soils present sediments lightly stratified, with thin strata. Its location is narrowly related with small plains with an important human activity that exists since remote times.
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Farmers mentioned that the “black” lands are cracked easily, that they keep high moisture inside, that they are sticky and that the lumps do not crumble easily. When they are dry these soils are not good for agriculture. They have no stones and are good agricultural lands, but they need to be fertilized.
Due to the good depth that it has, this soil type has been long time cultivated, what made them suitable for the human accessions. An example of it are the areas of “black” lands located near to the area of Cartagena city, where diverse populations have been installed since more than two millenniums. Results of the respective field description appear in Table 2. Texture of these soils vary from silt-clay to clay-silt, and its structure is simple granular.
Table 2: rural characterisation of three soil types in El Beal, Murcia, Spain. PROPERTIES SOIL CLASSES BLACK MUD RED Loose, dry Dusty Loose with sand DRY CONSISTENCE Loose Sticky Weighing Sticky Viscose No viscose HUMIDITY TEXTURE To shape crevice Clayish No viscose MOISTURE Moisture retention No moisture No moisture RETENTION retention retention FERTILITY Good soil, but need Need fertilising Very fertile fertilising WORKLY Is good to work Weighing in damp Easy to work ground and dry SALINITY The water is salty The water is salty The water is salty Soil type 2: Muddy Lands The farmers mentioned that the lands of “mud” get dried off strongly and form cracks, that these soils are sticky and viscous when they are humid, and that they form hard lumps when they are dry. If they are prepared on time they retain high moisture, nevertheless they need irrigation in order to let the plants sprout after sowing. Mud lands are constituted by soils of dark colours and thin textures in the surface. They have a granular structure in the superficial horizons and subangular blocks are present in the subsoil. They present cracks that can make deeper depending on the thickness of the clay sediments.
In El Beal site the soils are very productive when they are irrigated. Results of the respective field description appear in Table 2. The size of the particles confirmed that the texture of these soils is predominantly clay and clay loam. The thickness of the horizons or caps can change from 40 up to 150 centimetres and with the content of organic matter. The content of organic carbon is high in the surface, diminishing gradually with the depth. Soil type 3: Red Lands Red lands do not need fertilizers, they are not sticky and are not cracked when are dried. These soils keep low moisture and their lumps are smooth. They can be easily worked, so most of the crops of the county are produced in these soils. Farmers consider the “red” land as the best agricultural land and they describe it as the product of the accumulation of materials transported by the water from the mountainous. Results of the field description appear in the Table 2.
On the surface medium size particles can been found. Texture is mostly loam with a big number silt lumps. The content of organic matter in these soils ranges from medium to high values, which can diminish gradually in depth or decrease irregularly.
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Soil type 4: Slate or Sluggish (weak) Lands Slate or sluggish (weak) lands are soft when they are wet, do not become hard, do not keep moisture, and are not sticky and neither cracked. These soils have bulky material with sand and stones in the surface, so they have low fertility. The information of texture indicates that there is predominance of stones and/or slates in the surface, where its name is derived from and by what they are easily identified. The location of these soils is narrowly related to small elevations (mounds). These soils have been found in La Azohía site, where dry land agriculture predominates. Principally crops are barley, oats, and almond trees. Results of the field description are presented in Table 3. Soil type 5: reddish or Moyas lands The farmers define the “reddish” lands as the characteristics of the Spanish east. They are very dry, hard lands, with presence of lumps or “tormos” hard as gravels. They get cracked very easily and keep high moisture. They are very fertile soils, or as the farmers say are strong (moya) soils. These lands have been found in the area of La Azohía, where the rains are extremely rare (<200 mm per year).
Reddish lands can be recognized by its colour and by the dried clay lumps, which makes these soils very heavy for the cultivation works. These lands, together with the “red” soils of El Beal, are the clay lands of the county, even their morphologic characteristics and management techniques are quite differentiated. Results of the field description appear in the Table 3.
Table 3: rural characterisation of two soil types in La Azohía, Murcia, Spain. PROPERTIES SOIL CLASSES SLATE REDDISH Hard and Clods DRY Loose CONSISTENCE Loose with sand Weighing Is smooth Sticky HUMIDITY TEXTURE Sand Sticky MOISTURE Moisture retention Moisture retention RETENTION FERTILITY No fertile Strong (good fertility) WORKLY Smooth to work Weighing to work PROBLEMS Dry land Dry land
Soil type 6: Sandy Lands The peasants of the Vega Media del Río Segura Segura site delimited three types of different lands. They mentioned that the “sandy”, free lands, are soft when they are wet and do not become hard. These soils are not sticky and do not get cracked. Moisture is quite good kept, nevertheless need to be watered often for good agricultural management. They are fertile soils and they can be easily worked. These lands are located in former riverbeds –Segura River- in thin stripes. Results of the field analyses on sandy soils are presented in Table 4. The information of texture indicates the predominance of the sand fraction (from 60 to 68 % of sand) in the surface. They are moderately fertile soils; the content of organic matter is inferior to 2 % and it decreases irregularly up to all 150 cm of depth. Soil type 7: Smooth Lands Smooth lands are soft, but harder than the “sands”, and appear small lumps. The farmers of the zone define them as heavy and sticky, without salt. These soils do not need fertilizers, and have little sand. They have a high moisture storage capacity, have a good fertility and are easy to work. These lands are commonly identified for its grey, whitish colour in the surface.
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For the farmers of this site “smooth lands” are the best agricultural lands and they describe them as the product of the accumulation of materials transported by the river. These lands are located close to the Segura River bed, so they seem to be relatively young soils. In the Table 4 results of the fields analyses of the “smooth” lands are presented. Texture of these soils ranges from silt to clay, and are heavy when wet due to their high percentage of clay, which causes the formation of small lumps, or tormos, when these lands are not regularly worked. Soil type 8: Hard Lands The farmers call “hard” lands to soils that dry off strongly and form big clay lumps and small cracks. They are sticky, less soft than the “sands” and the “soft” ones. If they are worked on time and regularly they keep moisture. Anyway, these lands need at least two flood irrigations in order to get a high yield of the crops.
Hard lands are formed by dark coloured soils. They have a granular structure in the topsoil and subangular blocks in the subsoil. They present cracks that go deeper than 25 centimetres, depending on the thickness of the clay sediments.
In the Vega Media del Río Segura area, these soils are very productive when they are under irrigation. The yield of the almond trees, apricots, peach trees and the vegetables is quite good. These soils are highly estimated by the farmers. The Table 4 shows the results of fields analyses of the “hard” lands. Table 4: Rural characterisation of three soil types in La Huerta de la Vega Media del Río Segura, Murcia, Spain. PROPERTIES SOIL CLASSES SAND SMOOTH HARD Loose with sand Hard, little clods Hard, clods DRY Very Smooth Weighing, viscose Very viscose HUMIDITY TEXTURE Loose with sand Smooth, whitish Smooth grey MOISTURE Moisture retention Moisture retention Moisture retention RETENTION FERTILITY Good fertility Need fertilization Good fertility WORKLY Smooth Easy to work Hard to work PROBLEMS The water is salty The water is salty The water is salty
One class or type or soil according to the taxonomic classification (FAO-ISRIC-ISSS, 1998) can be identified by the farmers of the area -rural classification- as several different land types.
In the Region of Murcia it is possible to find soils with a different genesis, due to different geological and pedogenetic processes. In relation with this, the size of the superficial granules of the soils, feature that depends on this soil genesis, is one of the different attributes by which the peasants identify the different land types. From an edaphogenetical point of view, these characters have influence on the type of the surface sediments that we can find (Grossman, 1983), which influences the agronomical and edaphical properties for every type of soil. The thin sediments seem to be the origin of the "mud" and "black" lands. The difference between both classes of lands is the presence of amorphous materials. It is believed that its origin is directly related to the alluvial influence, what means that it have relation with the existence of thin sediments that had a direct origin in beds of lakes and rivers. The “reddish” and “red” lands have been considered to be paleosoils, known also as “red Mediterranean soils”. These lands would be considered by taxonomic classification as Luvisols (FAO-ISRIC-ISSS, 1998). They have a reddish B horizon, due to the strong liberation of oxides of iron, with a secondary enrichment in clay. These soils are less abundant, and are relegated to the more geomorphological stable positions. These lands need to be preserved because they are elements of great importance for the natural environment and for the landscape of the Region of Murcia.
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The silt sediments originated the “soft” and “hard” lands, which nowadays are located in margin of the Segura River, which allows identifying them as the younger soils. Its origin seems to be in more recently deposited sediments, and in some cases also for the accumulation of organic matter. These soils can be classified as Fluvisols (FAO-ISRIC-ISSS, 1998).
The anthropogenic influence of the works for the soil recovery used by the farmers, have changed some soil properties, especially into the zones of irrigation, where the pH has suffered some variations. In those areas where dry land agriculture has been traditionally practised, and in areas opened recently to the crops, the human influence has been historically less.
Conclusions The farmer soil classification shows knowledge of soil quality inside his plots. The programs of sustainable development must consider the rural knowledge, to detect technical, ecological and management problems of the soils.
The rural classification showed a wide knowledge on the use and managing of the resources to plot level. The peasant knows in detail the soil resource that often exceeds to the technical knowledge, what allows to apply technologies adapted to the real needs of the producers, and to establish communication for their active participation in the conservation of the natural resources. In any case, this does not mean at all that taxonomic classifications must be obviated; even more both systems must be complementary for these purposes.
There are quite a good coincidence between the physical characteristics known for the different types of soils and the rural soils described by the producers, especially for texture and color. Nevertheless, due to the use and management of soils by the farmers of the zone, agricultural soils have been altered and so differ from natural lands.
For the farmers of this region the best farming soils seems to be the “black” lands. With the rural classification we obtained a greater number of soil types than with the taxonomic classification (FAO- ISRIC-ISSS, 1998) at Reference level. Programs supporting sustainable development must consider the rural knowledge, since it allows recovering some management technologies for a better conservation of the soil resource.
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