DETERMINING PHYSICAL AND CHEMICAL PROPERTIES OF E THREE WETLAND TYPES
CHAPTER ONE
INTRODUCTION
Wetland soils, otherwise designated hydromorphic soils, may be
defined as soils whose properties are influenced by the presence, either
seasonally or perennially of standing water within their profiles
(Eshett et al., 1986). Wetland soils are those soils, which are
water saturated during most of the months (Onyekwere and Akpan-Idiok,
1999). Wetland soils occur commonly in swamps, floodplains, inland
valleys, and other areas of low topography and are usually underlain by
impervious parent material which prevents or retards infiltration of
water emanating from rainfall, irrigation, river inundation, surface
run-off or seepage from surrounding highlands.
Wetland cultivation is now being emphasized (Okusami and Rust, 1992;
Ogban and Babalola, 2003, 2009) to supplement the uplands where soil
productivity and crop yields have declined due to severe accelerated
erosion and degradation (Lal, 1988), accentuated by farmers mining the
physical, chemical and biological fertility of their soils (IITA, 1990).
The wetlands are reputed to produce over 90% of crops grown on uplands, (Ogban et al.,
2011) and are therefore more important than 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.
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 or
solution phosphorus.
Widespread deficiencies of phosphorus have been reported (Nnoke,
1980; Dyboh, 1999) as a major constraint to crop production in
Southeastern Nigeria due to over cultivation, low total P and
insufficient replenishment of lost P from soils. A major loss leading to
phosphorus deficiency in these soils was attributed to phosphorus
fixation by sesquioxides. According to Osodeke and Kamalu (1992), Ibia
and Udo (1993), Sharawat et al., (2001), Osodeke (2000), Abekoe
and Sharawat (2001), (2003) and Osodeke and Ubah, (2005), highly
weathered soils of the humid tropics rich in 1:1 clay minerals
(kaolinitic clays) and high contents of sesquioxides are not only low in
phosphorus but the applied soluble phosphorus is converted into forms
not readily available to crops and as such limit crop production and
productivity. This immobilization often described as fixation,
precipitation, sorption or adsorption depends on the amount of
phosphorus added, the nature of the fixation product and on the soil
physical and chemical properties (Osodeke, 2000).
There is inadequate information on the phosphorus status of wetland
soils in Akwa Ibom State. Therefore, the study seek to investigate the
phosphorus status of three wetland types in Akwa Ibom State.
The following were the specific objectives:
- To determine some physical and chemical properties of e three wetland types.
- To assess the levels of total P, organic inorganic inorganic and available phosphorus in three wetland types.
- To determine the phosphorus retention capacity of three wetland types.
- To assess the relationship among three wetland types.
CHAPTER TWO
LITERATURE REVIEW
2.1 Wetlands
Wetland is a type of landform that has been defined variously by different
DETERMINING PHYSICAL AND CHEMICAL PROPERTIES OF E THREE WETLAND TYPES