Ancient igneous rocks underly the major part of the district. Strongly metamorphosed ancient sediments occur along the western boundary. There are also important areas of relatively young unconsolidated sediments in the south and southeast. Dahomeyan gneiss and schist’s occupy most of the plains proper. Basic gneiss forms a number of large inselbergs (isolated rocky hills) in the north and center of the belt.
Small rock outcrops are also common in the north close to the inselbergs but are rare in south and southeast. The eastern belt of acidic gneiss consists mainly of the grained metamorphosed rocks rather richer in minerals than the rocks in the western belt and with many fewer quarts veins.
Recent alluvium occupies the Volta flood plains and the valleys of the major streams on the plain. There are no known mineral deposition of commercial and economic value in the area, except for oyster shell deposits at Volivo and its surroundings and clays of various types occurring in different places used for pottery and for the making of tiles and bricks.
Soils And Suitability For Agriculture
The predominant soil types in the district are the black clays classified as Akuse series and occupies the central to eastern parts of the district. The soils are highly elastic when wet but become hard and compact when dry and then crack vertically from the surface. This renders the soil unsuitable for hand cultivation.
Cultivation in the Akuse series dominated areas is confined mainly to small amounts of subsistence cropping of cassava, okro, maize and other vegetables. The short type grassland covering the Akuse series provides extensive grazing fields.
The Black clays are considered highly suitable for development mechanized irrigation farming. At the gentle foot slopes of the Akwapim Range north of Dodowa, Agomeda and Ayikuma occurs an accumulation of slope wash from the hills.
The slope wash material consists predominantly of the Oyarifa series. These are deep, red, well-drained loamy soils. Here crops such as cassava, cocoyam and to a larger extent maize are best suited. Mangoes are also largely grown in the Dodowa areas
The soil types, which occur further east of Dodowa, within the Doryumu and Kordiabe areas, are of the Simpa-Doryumu-Agortor-Association. These are brownish gray, slight humus, medium or coarse sand, underlain by a hard porous gristly loam.
The soils have low nutritional status and are quick in becoming parched after the end of the rainy season. Main crops grown here include pepper, okro, watermelon and maize.
Other soil types identifiable are those classified locally as the Agortor series found on the extreme eastern to south-eastern part of the district around Agortor, Dawa and Minya.
The soil here consists of gray-brown soils loamy for about 15-30 centimeter the surface than abruptly changing to an impervious clay which contains lime concretion below a depth of 60 centimeters. The topsoil rapidly becomes draughty during the dry seasons.
This type of soil fairly supports any level of crop production. Most parts of the area are, however, left for grazing purposes. In the extreme north and northeast of the district occurs the Volta Alluvium, which makes up the Volta flood plain.
The soils classified as an association of Amo and Tefle series consists more or less have poorly drained pale-coloured sandy silty and clay soils developed in recent or contemporary Volta Alluvium.
The soils appear to be moderately well supplied with nutrients under natural conditions and are easily workable even with simple implements. A greater portion of it in recent past was placed under extensive sugar cane cultivation to feed the now collapsed Asutsuare Sugar Factory.
The same fields are currently place under extensive rice cultivation making the flood plain soils, one of the most fertile soils in the Dangme West District.
At the coastal south, the predominant soil type is associated with coastal sand dunes, backed by a discontinuous series of narrow, saline or brackish lagoons. These soils to some extent support coconut growth.
Lastly, the type of soils classified as Toje-Agortor series covers the area along the road to Ada and located at the southern sections of the Agortor series. It is made up of a mixture of red soils developed over tertiary deposits on the uplands and gray-brown impervious clays of Agortor series. These soils absorb moisture freely except when left bare.
Under the prevailing climatic conditions, they tend to be draughty in the topsoil, but lower layers have a good moisture storage capacity. These soils, to some extent, are favoured for cultivation as they are easily workable.
However, the application of frequent cover crops or the addition of farmyard manure will be essential if intensified crop production is to be maintained.