Variability of Some Properties of the Nun River Plain Soils in Bayelsa State, Nigeria

Whereas studies on spatial variability of soil properties on toposequences are well documented, information on the variability of characteristics of floodplain soils is lacking. This study, therefore, evaluates the status and variability of the soil properties in three physiographic units in two locations on the Nun River floodplain. Silt-sized particles dominated soil texture and soil texture variability due to stratification associated with fluvial parent materials and the recentness of the deposits. The pH values ranged from 5.76 to 6.30, and pH was the least variable characteristic. Organic C, total N and available P were highly variable in all the physiographic units of Odoni. Odi soils and the distribution of these properties decreased irregularly down the profiles, revealing organic matter as the primary source of total N and available P. Calcium was the dominant cation in the exchange complexes of the soils, and Ca2+ variability was irregular. At the same time, primary, Mg2+ and K+ were highly variable (CV≥35%) in all the physiographic units of the two locations. Though exchangeable acidity values were high (above 1cmol/kg) across depths, physiographic unit and location, pH values were above 5.5, and no soil acidity problem is envisaged in these soils. Exchangeable bases and acidity variability results reflected differences in the source of parent materials and possibly, the degree of hydromorphism. Bush burning and removal of crop residues should be avoided to maintain organic matter in these soils. The most significant constraints to agricultural intensification are flooding, wetness and fertility constraints.