Morphology, organic carbon and dissolved nutrients in groundwater table in two benchmark wetlands sites in Nigeria

Wetland soils in two benchmark sites located in the tall/grass land savanna (Edozhigi) and in the Rain Forest (Ibadan) were selected in order to study the soil morphological characteristics, organic carbon contents, and the nutrient dynamics (P, Ca, Mg, Fe, and NH4-N) in the ground water table when rice was planted. Morphologically these soils are gleyed, mottled, with a hue of 10 YR, and low chroma that reflects poor drainage (i.e. aquic soil moisture regime). Th e soils are deep; more than 1.20 m in depth. Th e soil organic carbon was high in the surface soils (between 0.6 and 2.15%) and fluctuated irregularly with depth. In addition, the ground water table fluctuated between 40-80 cm depth within all the soils at both sites. Following soil submergence, water soluble P, Ca, Mg, Fe, and NH4-H increased in the fi rst week and began to decline as from the 56 - 70 days aft er transplanting (DAT) which coincided with the tillering stage of rice plants. Th e Nitrate-N concentration was very low (≤4 mg/l) at both sites. Th is flooding during the rainy seasons would benefi t rice plants and the high organic carbon contents in the soils could be a substantial factor in the maintenance of these soils for the cultivation of arable crops during the dry seasons.