Reading N. 1: SOILS AND TOPOGRAPHY in ECUADOR

SOILS AND TOPOGRAPHY in ECUADOR

Topography
Ecuador is divided into three continental regions--the Costa, Sierra, and Oriente areas, plus one insular region--the Galápagos Islands (Ecuador, 2001). The Coastal region is located between the Pacific Ocean and the Andes Mountains, and it consists of lowlands and mountains. The lowlands are generally below 200 metres, whereas the Coastal Mountains ("Cordillera Costanera"). The width of the Costa ranges between 15 and 150 kilometres.

The Sierra includes two major chains of the Andes Mountains that run north - South, the Cordillera Occidental (Western Chain) and Cordillera Oriental (Eastern Chain). The Western Chain contains Ecuador's highest peak, 6,267 metre Mount Chimborazo. The Oriente consists of two subregions: the Andean piedmont and the Eastern lowlands. The piedmont drops from a height of 3,353 metres to the lowlands, which spread out at an altitude of 150 to 300 metres.

Soils
The extremely variable topography of the country is associated with a complex mosaic of soils.

The Coastal littoral, 

Located between the Pacific Ocean and the western Andes possesses an abundance of hydromorphic soils particularly in the well-watered parts, which have moderate to low drainage, and moderate fertility. It contains soils derived from deposits of diverse origins influenced by volcanic activity of the Andes, aeolian transport of volcanic ashes and alluvial deposits, all subjected to intense weathering.

In the temperate Andean eco-zone 

(see below under ecozones), soils vary somewhat depending upon rainfall. It should be noted that classification of Andean soils is notoriously complex; details and equivalencies between systems of classification are available. The portion of the temperate area frequently classified as a low montane spiniferous steppe, with rainfall of less than 500 mm includes the following soils:

(a) Durandept, sandy loams, with a calcareous layer located above a duripan placed at a depth of 70 cm - these are soils that if irrigated support a variety of annual crops, lucerne, oats and Kikuyu grass;

(b) Durustoll, generally located on slopes, over fine ashes and also with an underlying duripan;

(c) Eutrandept, loamy soils with very fine ash, low water retention, pH 7; and lastly

(d) Torripsamment, very sandy soils, with less than 1 percent organic matter and pH 8. When rainfall increases to 500-1,000 mm, the zone is classified as low montane dry forest, and includes very variable soils, most frequently derived from volcanic ashes. These are clayey loams, black soils, that support productive stands of lucerne if irrigated. The low montane humid forest zone is encountered in areas with 1,000 to 2,000 mm, and has similar soils to the previous one.

The cold temperate eco-zone 

Is found at high altitudes. Within it, the Paramo (or cold high steppe) is the typical landscape, receiving 250-500 mm rainfall. In general terms, Paramo soils are of volcanic origin; these include soils derived from recent volcanic ashes, and those derived from metamorphic and igneous rocks. Those of the northern and central Paramos are generally Andisols, young, undifferentiated, high in organic matter, with high water retention capacity, highly permeable and resistant to erosion. Nevertheless, once they lose these physical properties as consequence of compaction, they begin to repel water. Soils of the southern Paramos are generally Inceptisols, derived from metamorphic rocks, older than the previous one, less fertile but have less capacity.

Soils of the Amazon piedmont, on the eastern slope of the Andes are mostly Inceptisols of low to medium fertility. It has soils with pH 5-5.8. In the lowland plains three main types of soils are recognized:

(a) alluvial sandy soils in the flatter portions along the rivers, seasonally cultivated with a variety of crops;

(b) black, fertile volcanic soils, in the plains located near the Napo River, and

(c) red ultisols in broken hills, characteristically acid and of low fertility.