Lameo, an indigenous method of soil conservation Farmers in the Andes have many traditional ways of enriching and conserving their soils. For example, a technology called may’kas refers to a process of enriching the soil, using nature’s means of transportation of mineral and organic materials, as is common in high mountain regions. In Oruro, Bolivia May’kas is done with the help of flowing water when the river has risen and with dust filtered from the wind (San Martín, 1988 and Rengifo, 1994). Volcanic ashes are also used. Zimmerer (1995) studied the geomorphology and the sediments in the Valle Alto, Cochabamba, Bolivia. Having analysed the soil with the C14 method, he estimates that the use of lameo (the technique of sediment trapping) goes as far back as 1500 BC. In some valleys of the Department of Cochabamba in the central part of Bolivia, farmers still practise the technique of lameo. To trap the sediment carried along by the rivers, flowing water is captured by altering the river’s course allowing it to flood the fields. In this way, farmers create their own soil. In the fields located further away from the river, they enrich the soil by mixing the sediments carried by the river with the existing soil. The technique of lameo represents the relationship between man and the river. In the same way that the flooding of the river helps to make the soil, it can also lead to the destruction of that very same soil. In order to alter the course of the river, so that it can flood the land, bocatomas (man-made openings or inlets) are made. Every time the river floods, the farmers have to rebuild these bocatomas. Capinota: a village practising lameo Rengifo (1994) describes how the farmers practise the technique of lameo in the Valley of Capinota, one of the valleys of the Department of Cochabamba, using the water of the river Arque. This technique is still being used even though a very intensive and commercially oriented agriculture has developed in this region. In the basin of the river Arque (2224 km²), which is the upper part of the basin of the Amazon river, cultivated as well as uncultivated areas can be found. The altitude varies between 2380 and 4820m a.s.l. The base flow of the river Arque is between 2 and 2.5 m³/s. When the river rises during the rainy season (from November to April), the flow is calculated to be 908 m³/s once every hundred years. During this season the river carries the sediments (up to 120g/l) in suspension. The colour of the sediments ranges from red to yellow and dark brown, depending on the area from which the water originates. Capinota is a village at 2380m a.s.l. situated where the rivers Arque and Rocha meet to become the river Caine. The climate is semi-arid with an average rainfall of 509 mm per year. The dry season is relatively cold while the rainy season is warmer. The average annual temperature is 18º C. It does not freeze during the dry season. The conditions for agriculture are good all the year round. The most important crops are potatoes, carrots, beets, onions, sweet potatoes, corn and alfalfa. There are also vineyards and fruit trees, such as peaches and apples. There are no fallow periods and the farmer’s fields are small (the average size is 3500 m², ranging between 600 and 6000 m²). Besides landowners producing for themselves, it is common to organise production in different ways, such as renting the land and producing on a share-cropping basis. The family is usually employed as labour. Preparing and ploughing the land is done manually and with oxen. The tractor is rarely used. The size of the area of lameo irrigation is 228 ha. and 210 farmers participate in it. They organise the lameo by dividing the land into sections. The maintenance of the canals and the bocatomas is the most important activity to be coordinated between the different sections. How it is done The farmers use a main canal with a capacity of 1500 l/sec. This canal is used by approximately 15 farmers, who irrigate their land with 60 to 120 l/sec. each. They are able to capture an average layer of sediment of 10 cm. in every field. This process takes from a few days to a month, depending river discharge, the water pressure and the distance of the bocatoma to each field. After some weeks of drainage the land is ploughed so the farmers can plant - mainly Dutch potatoes, grown for the market.The various activities thus include: the preparation of the land, letting in the water containing the sediment, and the drainage of excess moisture. During the month of December a 30 cm high dyke is built around the field. If farmers want to obtain a layer of sediment thicker than 10 cm, this dyke can be raised up to one meter high with mud or peat blocks. The building of the dykes takes from half to a whole day depending on the size of the field. The building of the higher dykes takes two or three days. Inside the field, between the dykes, they build small canals which are 80cm wide and 35 cm deep so that the water can be distributed as equally as possible over the land. It usually takes one or two days to build these small canals. The river water, full of sediment, flows into the fields at a rate of 60 and 120 l/s and with a speed of 0.7 to 1 m/s. To distribute the water as equally as possible, farmers closely monitor the irrigation canals and repair them with mud when necessary. Sometimes the speed of the water has to be slowed down and plant material and branches are placed in the canals to do this. At the lower end of the field (close to the river) the farmers make furrows some 30cm wide every 5m to drain the excess water, thereby leaving the land under 12 to 15cm of water. In the final stage of the lameo, water inlets are closed off so that the excess moisture can be drained, enabling the farmers to prepare the land for planting and sowing. The drainage takes about one month. Why use lameo? Because the lameo technique is used every 1 to 3 years, it is an essential part of the agricultural system. During the research period we were able to verify that farmers used the sediment trapping technique in 30% of all the farmland of the area (see map). This is in fact the land where they grow potatoes, their most important crop. The soil is prepared by mixing the layer of mud (the sediment), the existing soil and adding chicken manure. The depth of the ploughing is approximately 20cm. After the potatoes have been planted, chemical fertilizers are added. There are several reasons why the farmers use this sediment trapping technique. In interviews they mentioned that when the soil has become "hard" (llink’i - an expression in Quechua meaning clay or heavy ground) and the mineral salts have come to the surface, crops can deteriorate. Another reason mentioned is that they have to keep their fields at an adequate height in relation to the level of the river. In some years, when there is little rain and therefore the river does not rise as much as usual, stones and rocks accumulate in the river bed. The level of the river is raised and the danger of flooding increases in the following rainy season. Evaluating local knowledge The sediment trapping technique, lameo, is a low-cost technology that only needs labour and local material, and it avoids the major investment needed to buy inputs. On the whole, the farmers consider their soil to be improved by it. There is no doubt that this technique affects the soil’s height, fertility, moisture content and mineral salt content. Another important aspect is that lameo helps to improve the health of the potato plant, by decreasing the amount of nematodes. It is not easy to scientifically evaluate a particular technology used by farmers. What do they mean by "the soil becomes hard"? The studied textures range from clear ("franca") to muddy. The internal drainage of the land is good because it lies higher than the rocky river bed. The presence of mineral salts like calcium and magnesium have been shown. There is a possibility that these salts act as a hardening substance that prohibits the ventilation of the soil. The estimates of erosion caused by water and wind in Bolivia are alarming. It is estimated that that 64% of the surface of the Department of Cochabamba is at least moderately eroded (CORDECO,1980). Erosion is caused by natural factors, but in fact, sediment in the river beds comes from the fields of the farmers up-stream. When we take the hydrographic basin as the unit of analysis, we understand why the farmers use this technique as a way to preserve and improve their soil. In areas that lie in the lower part of the basin, they make use of the sediments that are freed by the impact of the rains on the upper part of the basin. In spite of the enormous efforts of farmers trying to improve the soil by means of sediment trapping, the danger of the river invading the reclaimed land still exists. This is the reason why the farmers have started to build cement walls to protect their land and their houses, so that they can better defend themselves against the whims and wiles of the river. Bert Boer and Ramón Castellón, PEIRAV, Casilla 4926, Cochabamba, Bolivia. References - Antunes de Mayolo, SE. 1990. Hidráulica costera prehispánica. Allpachis 11-37. Lima. - CORDECO, 1980. Análises de problemas y potenciales en el desarrollo regional de Cochabamba: CORDECO. - Rengifo, G. 1994. El suelo agropecuario en las culturas Andinas y en occidente moderno. PRATEC, Lima. - San Martín, J. 1988. Manejo de may’kas en tecnologías campesinas de los Andes. Primer seminario taller Altiplánico de revaloración del conocimiento Andino: 106-114. Oruro. - Zimmerer, K. 1995. The origin of Andean irrigation. In: Nature, Vol. 378: 481-483. << country/story review