Variations in selected soil physical properties with landforms and slope within an inland valley ecosystem in Ashanti region of Ghana
2011
Obalum, S.E.,University of Nigeria, Nsukka (Nigeria). Dept. of Soil Science | Nwite, J.C.,Federal Coll. of Agriculture, Ishiagu (Nigeria). Dept. of Crop Production Technology | Oppong, J.,Soil Research Inst., Kumasi (Ghana) | Igwe, C.A.,University of Nigeria, Nsukka (Nigeria). Dept. of Soil Science | Wakatsuki, T.,Kinki Univ., Nara (Japan). School of Agriculture
One peculiar feature of the inland valleys abundant in West Africa is their site-specific hydrology. Development and management of these land resources under the increasingly popular sawah (a system of bunded, puddled and levelled rice field with facilities for irrigation and drainage) technology is a promising opportunity for enhancing rice production in the region. Three landforms (river levee, elevated area and depressed area) were identified within a sawah field located in an inland valley at Ahafo Ano South District of Ghana. Each of these landforms was topsoil-sampled along on identified gradient (top, mid and bottom slope positions) in order to determine particle size distribution, bulk density, total porosity and field moisture content. The soil is predominantly clayey. There were no variations in the particle size distribution among the slope positions in the river levee. Overall, the river levee had lower silt content than the elevated and the depressed landforms. The bulk density, total porosity, and gravimetric moisture content indicated relative improvements only in the depressed area in the following order: bottom more than mid more than top slope. Irrespective of slope position, the three landforms differed in the charcateristics studied in the following order: depressed more than river levee more than elevated. The sand fraction impacted negatively on the silt fraction and bulk density of the soil, both of which controlled the soil moisture status. Despite the fairly low silt content of the soil, the silt fraction strongly influenced the gravimetric moisture content (R2 = 0.80), the soil bulk density influenced the gravimetric moisture content (R2 = 0.90). It is concluded that: (1) since the land forms more prominently influenced the measured characteristics than the slope positions, the former should take pre-eminence over the latter in soil suitability judgment; (2) with respect to moisture retention, variations in silt fraction and bulk density of this and other clayey inland-valley soils should be used as guide in site selection for sawah development.
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