English

Mbene Kenneth,Suhtening Aaron,Nkafu Fomenky Norbert,Bih Che Vivian,Emmanuel Suh Cheo

doi:10.5897/ajar2017.12530

Abstract

The Eastern flank of Mount Cameroon is made up of human settlement and agricultural activities. Determination of phosphorus (P) fixation characteristics of soils around this region is important for a clean environment and economic fertilizer application. The objectives of this study were to evaluate P-fixation characteristics of soils within the region and identify factors contributing to P-fixation. Composite surface soil samples from five sites (between 36 to 1006 m) were collected and analyzed for physicochemical properties and P-fixation capacity. Fixation data were obtained by equilibrating the five soil samples with 25 ml of KH2PO4 in 0.01 M CaCl2, containing 0, 10, 50, 100, 250 and 500 mg L-1. Phosphorus-fixation data were fitted to Langmuir and Freundlich adsorption models and the relationship between P-fixation and soil properties was determined. The adsorption maximum (KL) for Freundlich model was the highest for Limbe - Man O’War Bay Road (LMR, 174.58 mg P kg-1), followed by SLR (34.12 mg P kg-1), Dibanda-Mutengene Road (DMR, 24.72 mg P kg-1), VAS and UPD (16.87 mg P kg-1). The Langmuir adsorption maximum for Vasingi (VAS), Upper Boduma (UPD), Sasse-Limbe Road (SLR), DMR, and LMR were 0.01, 0.02, 0.01, 0.02 and 0.05 mg P kg-1, respectively. The phosphate adsorption isotherm gave good fit adopting Freundlich (r = 0.98 to 0.99). KF correlated with pH (r = - 0.87), Ca (r = - 0.87), exchange acidity (r = 0.87), and clay (r = 0.67). This study illustrated that P sorption isotherm in relation to soil properties can be used as a tool for P management in sustainable crop production.   Key words: Phosphorus fixation, adsorption isotherms, soil physicochemical properties, volcanic soils, Mount Cameroon.

Highlights

Phosphorus plays a very vital role in plant germination, growth and maturation
The chemistry of soil inorganic P strongly depends on the composition and crystalline nature of the solid phase of soils and the ionic nature of soil solution P (Mehmood et al, 2010)
Particle size fraction indicates that the textural class of the surface composite soil samples ranged from loam (VAS), through clayey loam (UPD, Sasse-Limbe Road (SLR) and LMR) to silty clay (DMR)

Summary

Introduction

The chemistry of soil inorganic P strongly depends on the composition and crystalline nature of the solid phase of soils and the ionic nature of soil solution P (Mehmood et al, 2010). The composition and crystalline nature of the solid phase of soils, and the ionic nature of soil solution P vary greatly; this variation influences the chemistry of soil P and has drawn the attention of many researchers. Fixation is said to have occurred when chemicals accumulate at the interface between solid phase and aqueous solution phase. This phenomenon determines the availability of native soil nutrients and the rates at which nutrients are applied to the soil as fertilizers. Phosphate ions are chemically unstable in soil solution, and readily react largely with oxides and hydroxides of aluminium (Al) and iron (Fe) found on clay surfaces for acidic soils and with the hydroxide of calcium (Ca) in calcareous soils to form less and more stable compounds (Bolan and Baskaran, 1996; Bolland et al, 2003)

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