LEDD issues in cropland: Spain and Canyoles River Basin

Editor's note 30 Apr 2012: Text source D111.

Modern agriculture is based on the use of chemicals, which are highly dependent on a non-renewable resource: oil. The sustainability of current agricultural practices is low and will result in a reduction in soil fertility once oil prices increase significantly or become exhausted. The main difficulties with oil dependent agriculture are: i) farmers lose their knowledge of traditional agriculture and it will be difficult to return to traditional agriculture as a result of that discontinuity of knowledge; and ii) soils are being depleted of organic matter and are becoming more dependent on mineral fertilizers, which only contribute to a short-term increase in soil fertility. This can be the beginning of the collapse of production, as once chemical fertilizers are no longer available, there will be neither knowledge nor natural fertility in the soils to maintain food production in the area.

Soil erosion

Soil erosion rates are high in Spain and the Júcar River watershed due to the lack of vegetation cover. Farmers use herbicides and ploughing to reduce and eliminate weeds and this reduces soil organic matter, increase soil sealing and soil erosion due to splash and sheet erosion. These LEDD conditions are mainly found on new and intensively managed farms such as orange and olive plantations and are also widespread in land used for cereal production, fruit orchards, olive groves and vineyards.

Soil organic matter decline

Forest soils at the Canyoles river basin show three to 15 percent organic matter content. Agricultural soils have 0.6 to three percent organic matter content with average values of one percent. These soils have a weak structure and low infiltration rates due to their lack of organic matter.

Soil compaction

The intensive use of machinery and the application of agricultural chemicals results in an increase in soil compaction. The bulk density is on average greater than 1 kg cm-3. The use of heavy machinery also results in disturbance of the soil.

Soil sealing

The use of concrete contributes significantly to the increase in soil sealing. Asphalt and concrete are widely used in road building to avoid erosion but this strategy results in increased runoff and soil and water losses. Farmers are increasing soil sealing by using asphalt and concrete to improve the surface of farm tracks, which facilitates easier access into their fields. Easy access to land is especially important during harvest when fruit needs to be picked and transported quickly.

Soil and water pollution

The extensive use of chemicals in agriculture is triggering an increase of nutrients and pesticides in watercourses and rivers. This is mainly an issue in groundwater where nitrates are widely found, and is resulting in water supply shortages in coastal areas where aquifers have become polluted. Some researchers have found a relationship with stomach cancer. The pollution of aquifers results in an increase in water exploitation from mountainous areas where water is unaffected by pollution, as there is little intensive agriculture in the mountains because the population migrated to the lowlands over 50 years ago.

Loss of biodiversity

Chemical-based farming and drip irrigation are contributing to a reduction in plant and animal biodiversity. As a result of a lack of ponds and irrigation ditches, amphibians have almost disappeared. This new type of intensive agriculture which uses chemical fertilizers and drip irrigation means that there is no vegetation to cover the soil between the rows of fruit trees

Aquifer depletion and the loss of traditional water management

Traditional irrigation in the Canyoles River basin was based on springs which emerge from karst aquifers. This is the basic water resource system in Mediterranean agriculture, as summers are hot and dry. The over exploitation of aquifers by the new citrus and olive plantations has resulted in the loss of these traditional springs.

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