CONCRETIONARY NODULES AS NUTRIENTS SINKS AND THEIR EFFECT ON PHOSPHATE ADSORPTION IN A PLINTHIC HAPLUSTALF

CONCRETIONARY NODULES AS NUTRIENTS SINKS AND THEIR EFFECT ON PHOSPHATE ADSORPTION IN A PLINTHIC HAPLUSTALF

Abstract:

This research focuses on the effects of concretionary nodules on nutrient composition of a Plinthic Haplustalf, and the effects of concretionary nodules on phosphate fractions and adsorption by the soils. Soil samples were collected from five farmers field in Biye northern guinea savannah,Nigeria, the soils collected were further designated as Biye north, Biye south, Biye east Biye west, and Biye central. The soil sampled were furtherseparated into Soils without concretionary nodules, soils mixed with concretionary nodules and concretionary nodules for detailed distributions of P and other microelement in the area. This study revealed that, the total phosphorus (Pt) of concretionary nodules in surface soils ranged from 604 to 1014 mg /kg while that of the soil without concretion was between 301.4 and 624.30 mg /kg in all locations. However, the available P in soils without concretion ranges from 10 to 15 mg/kg. Although the available P was low, the concentration was relatively higher than the concentration in soils with concretion and three times higher than the concentration in concretionary nodule. Furthermore, concretions were shown to accumulate high concentration of the total elements analysed. In the soils with concretionary nodules, most P recovered by sequential extraction was in the residual (276 – 697 mg/kg) and potentially bio-available fractions (43 – 55.8 mg/kg). The exchangeable P fraction (NaHCO3-P) of the soils held the least percentage (2 – 5%) of the total P in the soils with concentrations ranging from (8 – 12.3 mg/kg) in all the locations.Organic P (Po) was also low.Phosphorus adsorption was highest when solution P concentration increases from 250 μg ml-1 to 1000 μg ml-1.The Langmuir and Freundlich adsorption isotherms both showed well fitted with the correlation coefficients (R2) that ranged from 0.89 to 0.96 in all the soils. The adsorption maximum (b) obtained from the Langmuir isotherm ranged from 28 mg P kg-1 soil in soil without concretion to 68 mg P /kg concretionary nodules. The constant related to viii bonding energy (K) calculated from the Langmuir adsorption model varied from 0.4 to 0.99 mg P /kg The Freundlich adsorption parameters also ranged from 0.87 in soils without concretion to 0.95 mg kg-1 in concretionary nodules and for the Freundlich isotherm constant (Kf) from 1.89 in soils without concretion to 1.99 in concretion.Phosphorus recovered was highest in soils without concretion. The concentration of P recovered range from 34 mg/mg P to 86 m/kg p in soils without concretions whileconcretions range from 38 to 73 m/kg P in all location.P recovery continues as a true equilibrium was not attained

CONCRETIONARY NODULES AS NUTRIENTS SINKS AND THEIR EFFECT ON PHOSPHATE ADSORPTION IN A PLINTHIC HAPLUSTALF

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