The wetlands are reputed to produce over 90% of crops grown on uplands, (Ogban, Effiong, Obi and Ibia, 2011) and are therefore as important as the upland farmlands in that they can be used in the wet season (mainly rice), dry season (cassava, yams, cocoyams, tomato and vegetables), and all year round for tree crop production. The wetlands thus forms an important component of the ecosystem in the State, therefore justifying the need to study them including their natural fertility with a view to recommending appropriate management options for crop production and putting them to other sustainable uses. Their fertility is important as nutrient depletion is one of the major constraints in tropical and sub-Saharan soils and P is one of the nutrients of concern or interest in agro-ecologies.

Phosphorus is one of major essential nutrient elements required by plants. It is the second most deficient plant nutrient element as more than ninety percent (90%) of the world soil require moderate to high phosphorus levels for optimum crop growth and development (Rashid, 1994). Phosphorus plays a vital role in energy transformation and photosynthesis. The quality of fruits, forages, vegetables and grain crops as well as disease resistance of crops are enhanced under adequate phosphorus availability (Sanyal and De Datta, 1991).

The major sources of phosphorus in the soil are the parent materials, inorganic fertilizers, plant and animal residues (Agbede, 2009). The availability of phosphorus to plants in soils is usually linked to the relative abundance of various forms of phosphorus, such as total phosphorus, organic phosphorus, inorganic phosphorus and available phosphorus.