Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Plant, Enviromental and Soil Sciences

First Advisor

Wayne H. Hudnall


Mangrove soils along the Guinea coast are among the most fertile and potentially suitable soils for rice production. Rice production success and feasibility is hampered by adverse soil chemistry conditions and the use of traditional farming methods. The objectives were to undertake a pedological investigation to characterize these soils during the wet and dry seasons, provide an understanding of fertility constraints, and develop a management plan to improve rice production. Seasonally and permanently flooded soils categories were recognized. Seasonally flooded soils are subjected to drainage and permanent protection from saltwater intrusion. These soils were correlated as Typic Endoaquerts, Typic Endoaquepts, or Hydraquentic Sulfaquepts. They are characterized by low ECEC, high Al saturation, imbalanced nutrients, and S toxicity when flooded. High ESP and salinity in recently drained soils, and low dry season moisture are limiting. Permanently flooded soils still used for traditional rice cultivation were correlated as Typic Sulfaquents. New subgroups--"Sodic" (ESP $\ge$ 15) for Endoaquerts and Endoaquepts, and "Psammentic" (sand $\ge$ 50%) for Sulfaquents great groups are proposed. Fertility constraints are: potential sulfate acidity, high salinity and ESP, nutrient imbalance, potential high Al saturation and toxicity, S and Fe toxicity. Inappropriate water control/management, cultural practices, and low yielding, non-resistant traditional rice varieties add to these constraints. Management recommendations for the seasonally flooded soils include: establish dike and canal systems to control floodwaters during the wet season; incorporate rice straw into the topsoil after harvesting; correct nutrient imbalance using nitrogen fertilization; initiate field experiments for N, P, and K effects on rice yield; and apply lime to neutralize Al and increase Ca in the soil. The suggested management system for permanently flooded soils includes: drainage and protection from saltwater intrusion and use the same seasonally flooded soils fertility management system. The use of stress-resistant and high yielding rice cultivars is strongly recommended. Adaptive and applied research is needed to develop lower-cost and locality-adaptive technologies to ensure sustainable food production on these soils to protect the environment and ensure sustainable agriculture for future generations.